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// SPDX-License-Identifier: GPL-2.0
/*
* Data Access Monitor
*
* Author: SeongJae Park <sj@kernel.org>
*/
#define pr_fmt(fmt) "damon: " fmt
#include <linux/damon.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/mm.h>
#include <linux/psi.h>
#include <linux/slab.h>
#include <linux/string.h>
#define CREATE_TRACE_POINTS
#include <trace/events/damon.h>
#ifdef CONFIG_DAMON_KUNIT_TEST
#undef DAMON_MIN_REGION
#define DAMON_MIN_REGION 1
#endif
static DEFINE_MUTEX(damon_lock);
static int nr_running_ctxs;
static bool running_exclusive_ctxs;
static DEFINE_MUTEX(damon_ops_lock);
static struct damon_operations damon_registered_ops[NR_DAMON_OPS];
static struct kmem_cache *damon_region_cache __ro_after_init;
/* Should be called under damon_ops_lock with id smaller than NR_DAMON_OPS */
static bool __damon_is_registered_ops(enum damon_ops_id id)
{
struct damon_operations empty_ops = {};
if (!memcmp(&empty_ops, &damon_registered_ops[id], sizeof(empty_ops)))
return false;
return true;
}
/**
* damon_is_registered_ops() - Check if a given damon_operations is registered.
* @id: Id of the damon_operations to check if registered.
*
* Return: true if the ops is set, false otherwise.
*/
bool damon_is_registered_ops(enum damon_ops_id id)
{
bool registered;
if (id >= NR_DAMON_OPS)
return false;
mutex_lock(&damon_ops_lock);
registered = __damon_is_registered_ops(id);
mutex_unlock(&damon_ops_lock);
return registered;
}
/**
* damon_register_ops() - Register a monitoring operations set to DAMON.
* @ops: monitoring operations set to register.
*
* This function registers a monitoring operations set of valid &struct
* damon_operations->id so that others can find and use them later.
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_register_ops(struct damon_operations *ops)
{
int err = 0;
if (ops->id >= NR_DAMON_OPS)
return -EINVAL;
mutex_lock(&damon_ops_lock);
/* Fail for already registered ops */
if (__damon_is_registered_ops(ops->id)) {
err = -EINVAL;
goto out;
}
damon_registered_ops[ops->id] = *ops;
out:
mutex_unlock(&damon_ops_lock);
return err;
}
/**
* damon_select_ops() - Select a monitoring operations to use with the context.
* @ctx: monitoring context to use the operations.
* @id: id of the registered monitoring operations to select.
*
* This function finds registered monitoring operations set of @id and make
* @ctx to use it.
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_select_ops(struct damon_ctx *ctx, enum damon_ops_id id)
{
int err = 0;
if (id >= NR_DAMON_OPS)
return -EINVAL;
mutex_lock(&damon_ops_lock);
if (!__damon_is_registered_ops(id))
err = -EINVAL;
else
ctx->ops = damon_registered_ops[id];
mutex_unlock(&damon_ops_lock);
return err;
}
/*
* Construct a damon_region struct
*
* Returns the pointer to the new struct if success, or NULL otherwise
*/
struct damon_region *damon_new_region(unsigned long start, unsigned long end)
{
struct damon_region *region;
region = kmem_cache_alloc(damon_region_cache, GFP_KERNEL);
if (!region)
return NULL;
region->ar.start = start;
region->ar.end = end;
region->nr_accesses = 0;
region->nr_accesses_bp = 0;
INIT_LIST_HEAD(&region->list);
region->age = 0;
region->last_nr_accesses = 0;
return region;
}
void damon_add_region(struct damon_region *r, struct damon_target *t)
{
list_add_tail(&r->list, &t->regions_list);
t->nr_regions++;
}
static void damon_del_region(struct damon_region *r, struct damon_target *t)
{
list_del(&r->list);
t->nr_regions--;
}
static void damon_free_region(struct damon_region *r)
{
kmem_cache_free(damon_region_cache, r);
}
void damon_destroy_region(struct damon_region *r, struct damon_target *t)
{
damon_del_region(r, t);
damon_free_region(r);
}
/*
* Check whether a region is intersecting an address range
*
* Returns true if it is.
*/
static bool damon_intersect(struct damon_region *r,
struct damon_addr_range *re)
{
return !(r->ar.end <= re->start || re->end <= r->ar.start);
}
/*
* Fill holes in regions with new regions.
*/
static int damon_fill_regions_holes(struct damon_region *first,
struct damon_region *last, struct damon_target *t)
{
struct damon_region *r = first;
damon_for_each_region_from(r, t) {
struct damon_region *next, *newr;
if (r == last)
break;
next = damon_next_region(r);
if (r->ar.end != next->ar.start) {
newr = damon_new_region(r->ar.end, next->ar.start);
if (!newr)
return -ENOMEM;
damon_insert_region(newr, r, next, t);
}
}
return 0;
}
/*
* damon_set_regions() - Set regions of a target for given address ranges.
* @t: the given target.
* @ranges: array of new monitoring target ranges.
* @nr_ranges: length of @ranges.
*
* This function adds new regions to, or modify existing regions of a
* monitoring target to fit in specific ranges.
*
* Return: 0 if success, or negative error code otherwise.
*/
int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges,
unsigned int nr_ranges)
{
struct damon_region *r, *next;
unsigned int i;
int err;
/* Remove regions which are not in the new ranges */
damon_for_each_region_safe(r, next, t) {
for (i = 0; i < nr_ranges; i++) {
if (damon_intersect(r, &ranges[i]))
break;
}
if (i == nr_ranges)
damon_destroy_region(r, t);
}
r = damon_first_region(t);
/* Add new regions or resize existing regions to fit in the ranges */
for (i = 0; i < nr_ranges; i++) {
struct damon_region *first = NULL, *last, *newr;
struct damon_addr_range *range;
range = &ranges[i];
/* Get the first/last regions intersecting with the range */
damon_for_each_region_from(r, t) {
if (damon_intersect(r, range)) {
if (!first)
first = r;
last = r;
}
if (r->ar.start >= range->end)
break;
}
if (!first) {
/* no region intersects with this range */
newr = damon_new_region(
ALIGN_DOWN(range->start,
DAMON_MIN_REGION),
ALIGN(range->end, DAMON_MIN_REGION));
if (!newr)
return -ENOMEM;
damon_insert_region(newr, damon_prev_region(r), r, t);
} else {
/* resize intersecting regions to fit in this range */
first->ar.start = ALIGN_DOWN(range->start,
DAMON_MIN_REGION);
last->ar.end = ALIGN(range->end, DAMON_MIN_REGION);
/* fill possible holes in the range */
err = damon_fill_regions_holes(first, last, t);
if (err)
return err;
}
}
return 0;
}
struct damos_filter *damos_new_filter(enum damos_filter_type type,
bool matching)
{
struct damos_filter *filter;
filter = kmalloc(sizeof(*filter), GFP_KERNEL);
if (!filter)
return NULL;
filter->type = type;
filter->matching = matching;
INIT_LIST_HEAD(&filter->list);
return filter;
}
void damos_add_filter(struct damos *s, struct damos_filter *f)
{
list_add_tail(&f->list, &s->filters);
}
static void damos_del_filter(struct damos_filter *f)
{
list_del(&f->list);
}
static void damos_free_filter(struct damos_filter *f)
{
kfree(f);
}
void damos_destroy_filter(struct damos_filter *f)
{
damos_del_filter(f);
damos_free_filter(f);
}
struct damos_quota_goal *damos_new_quota_goal(
enum damos_quota_goal_metric metric,
unsigned long target_value)
{
struct damos_quota_goal *goal;
goal = kmalloc(sizeof(*goal), GFP_KERNEL);
if (!goal)
return NULL;
goal->metric = metric;
goal->target_value = target_value;
INIT_LIST_HEAD(&goal->list);
return goal;
}
void damos_add_quota_goal(struct damos_quota *q, struct damos_quota_goal *g)
{
list_add_tail(&g->list, &q->goals);
}
static void damos_del_quota_goal(struct damos_quota_goal *g)
{
list_del(&g->list);
}
static void damos_free_quota_goal(struct damos_quota_goal *g)
{
kfree(g);
}
void damos_destroy_quota_goal(struct damos_quota_goal *g)
{
damos_del_quota_goal(g);
damos_free_quota_goal(g);
}
/* initialize fields of @quota that normally API users wouldn't set */
static struct damos_quota *damos_quota_init(struct damos_quota *quota)
{
quota->esz = 0;
quota->total_charged_sz = 0;
quota->total_charged_ns = 0;
quota->charged_sz = 0;
quota->charged_from = 0;
quota->charge_target_from = NULL;
quota->charge_addr_from = 0;
quota->esz_bp = 0;
return quota;
}
struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
enum damos_action action,
unsigned long apply_interval_us,
struct damos_quota *quota,
struct damos_watermarks *wmarks)
{
struct damos *scheme;
scheme = kmalloc(sizeof(*scheme), GFP_KERNEL);
if (!scheme)
return NULL;
scheme->pattern = *pattern;
scheme->action = action;
scheme->apply_interval_us = apply_interval_us;
/*
* next_apply_sis will be set when kdamond starts. While kdamond is
* running, it will also updated when it is added to the DAMON context,
* or damon_attrs are updated.
*/
scheme->next_apply_sis = 0;
INIT_LIST_HEAD(&scheme->filters);
scheme->stat = (struct damos_stat){};
INIT_LIST_HEAD(&scheme->list);
scheme->quota = *(damos_quota_init(quota));
/* quota.goals should be separately set by caller */
INIT_LIST_HEAD(&scheme->quota.goals);
scheme->wmarks = *wmarks;
scheme->wmarks.activated = true;
return scheme;
}
static void damos_set_next_apply_sis(struct damos *s, struct damon_ctx *ctx)
{
unsigned long sample_interval = ctx->attrs.sample_interval ?
ctx->attrs.sample_interval : 1;
unsigned long apply_interval = s->apply_interval_us ?
s->apply_interval_us : ctx->attrs.aggr_interval;
s->next_apply_sis = ctx->passed_sample_intervals +
apply_interval / sample_interval;
}
void damon_add_scheme(struct damon_ctx *ctx, struct damos *s)
{
list_add_tail(&s->list, &ctx->schemes);
damos_set_next_apply_sis(s, ctx);
}
static void damon_del_scheme(struct damos *s)
{
list_del(&s->list);
}
static void damon_free_scheme(struct damos *s)
{
kfree(s);
}
void damon_destroy_scheme(struct damos *s)
{
struct damos_quota_goal *g, *g_next;
struct damos_filter *f, *next;
damos_for_each_quota_goal_safe(g, g_next, &s->quota)
damos_destroy_quota_goal(g);
damos_for_each_filter_safe(f, next, s)
damos_destroy_filter(f);
damon_del_scheme(s);
damon_free_scheme(s);
}
/*
* Construct a damon_target struct
*
* Returns the pointer to the new struct if success, or NULL otherwise
*/
struct damon_target *damon_new_target(void)
{
struct damon_target *t;
t = kmalloc(sizeof(*t), GFP_KERNEL);
if (!t)
return NULL;
t->pid = NULL;
t->nr_regions = 0;
INIT_LIST_HEAD(&t->regions_list);
INIT_LIST_HEAD(&t->list);
return t;
}
void damon_add_target(struct damon_ctx *ctx, struct damon_target *t)
{
list_add_tail(&t->list, &ctx->adaptive_targets);
}
bool damon_targets_empty(struct damon_ctx *ctx)
{
return list_empty(&ctx->adaptive_targets);
}
static void damon_del_target(struct damon_target *t)
{
list_del(&t->list);
}
void damon_free_target(struct damon_target *t)
{
struct damon_region *r, *next;
damon_for_each_region_safe(r, next, t)
damon_free_region(r);
kfree(t);
}
void damon_destroy_target(struct damon_target *t)
{
damon_del_target(t);
damon_free_target(t);
}
unsigned int damon_nr_regions(struct damon_target *t)
{
return t->nr_regions;
}
struct damon_ctx *damon_new_ctx(void)
{
struct damon_ctx *ctx;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return NULL;
init_completion(&ctx->kdamond_started);
ctx->attrs.sample_interval = 5 * 1000;
ctx->attrs.aggr_interval = 100 * 1000;
ctx->attrs.ops_update_interval = 60 * 1000 * 1000;
ctx->passed_sample_intervals = 0;
/* These will be set from kdamond_init_intervals_sis() */
ctx->next_aggregation_sis = 0;
ctx->next_ops_update_sis = 0;
mutex_init(&ctx->kdamond_lock);
ctx->attrs.min_nr_regions = 10;
ctx->attrs.max_nr_regions = 1000;
INIT_LIST_HEAD(&ctx->adaptive_targets);
INIT_LIST_HEAD(&ctx->schemes);
return ctx;
}
static void damon_destroy_targets(struct damon_ctx *ctx)
{
struct damon_target *t, *next_t;
if (ctx->ops.cleanup) {
ctx->ops.cleanup(ctx);
return;
}
damon_for_each_target_safe(t, next_t, ctx)
damon_destroy_target(t);
}
void damon_destroy_ctx(struct damon_ctx *ctx)
{
struct damos *s, *next_s;
damon_destroy_targets(ctx);
damon_for_each_scheme_safe(s, next_s, ctx)
damon_destroy_scheme(s);
kfree(ctx);
}
static unsigned int damon_age_for_new_attrs(unsigned int age,
struct damon_attrs *old_attrs, struct damon_attrs *new_attrs)
{
return age * old_attrs->aggr_interval / new_attrs->aggr_interval;
}
/* convert access ratio in bp (per 10,000) to nr_accesses */
static unsigned int damon_accesses_bp_to_nr_accesses(
unsigned int accesses_bp, struct damon_attrs *attrs)
{
return accesses_bp * damon_max_nr_accesses(attrs) / 10000;
}
/* convert nr_accesses to access ratio in bp (per 10,000) */
static unsigned int damon_nr_accesses_to_accesses_bp(
unsigned int nr_accesses, struct damon_attrs *attrs)
{
return nr_accesses * 10000 / damon_max_nr_accesses(attrs);
}
static unsigned int damon_nr_accesses_for_new_attrs(unsigned int nr_accesses,
struct damon_attrs *old_attrs, struct damon_attrs *new_attrs)
{
return damon_accesses_bp_to_nr_accesses(
damon_nr_accesses_to_accesses_bp(
nr_accesses, old_attrs),
new_attrs);
}
static void damon_update_monitoring_result(struct damon_region *r,
struct damon_attrs *old_attrs, struct damon_attrs *new_attrs)
{
r->nr_accesses = damon_nr_accesses_for_new_attrs(r->nr_accesses,
old_attrs, new_attrs);
r->nr_accesses_bp = r->nr_accesses * 10000;
r->age = damon_age_for_new_attrs(r->age, old_attrs, new_attrs);
}
/*
* region->nr_accesses is the number of sampling intervals in the last
* aggregation interval that access to the region has found, and region->age is
* the number of aggregation intervals that its access pattern has maintained.
* For the reason, the real meaning of the two fields depend on current
* sampling interval and aggregation interval. This function updates
* ->nr_accesses and ->age of given damon_ctx's regions for new damon_attrs.
*/
static void damon_update_monitoring_results(struct damon_ctx *ctx,
struct damon_attrs *new_attrs)
{
struct damon_attrs *old_attrs = &ctx->attrs;
struct damon_target *t;
struct damon_region *r;
/* if any interval is zero, simply forgive conversion */
if (!old_attrs->sample_interval || !old_attrs->aggr_interval ||
!new_attrs->sample_interval ||
!new_attrs->aggr_interval)
return;
damon_for_each_target(t, ctx)
damon_for_each_region(r, t)
damon_update_monitoring_result(
r, old_attrs, new_attrs);
}
/**
* damon_set_attrs() - Set attributes for the monitoring.
* @ctx: monitoring context
* @attrs: monitoring attributes
*
* This function should be called while the kdamond is not running, or an
* access check results aggregation is not ongoing (e.g., from
* &struct damon_callback->after_aggregation or
* &struct damon_callback->after_wmarks_check callbacks).
*
* Every time interval is in micro-seconds.
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_set_attrs(struct damon_ctx *ctx, struct damon_attrs *attrs)
{
unsigned long sample_interval = attrs->sample_interval ?
attrs->sample_interval : 1;
struct damos *s;
if (attrs->min_nr_regions < 3)
return -EINVAL;
if (attrs->min_nr_regions > attrs->max_nr_regions)
return -EINVAL;
if (attrs->sample_interval > attrs->aggr_interval)
return -EINVAL;
ctx->next_aggregation_sis = ctx->passed_sample_intervals +
attrs->aggr_interval / sample_interval;
ctx->next_ops_update_sis = ctx->passed_sample_intervals +
attrs->ops_update_interval / sample_interval;
damon_update_monitoring_results(ctx, attrs);
ctx->attrs = *attrs;
damon_for_each_scheme(s, ctx)
damos_set_next_apply_sis(s, ctx);
return 0;
}
/**
* damon_set_schemes() - Set data access monitoring based operation schemes.
* @ctx: monitoring context
* @schemes: array of the schemes
* @nr_schemes: number of entries in @schemes
*
* This function should not be called while the kdamond of the context is
* running.
*/
void damon_set_schemes(struct damon_ctx *ctx, struct damos **schemes,
ssize_t nr_schemes)
{
struct damos *s, *next;
ssize_t i;
damon_for_each_scheme_safe(s, next, ctx)
damon_destroy_scheme(s);
for (i = 0; i < nr_schemes; i++)
damon_add_scheme(ctx, schemes[i]);
}
/**
* damon_nr_running_ctxs() - Return number of currently running contexts.
*/
int damon_nr_running_ctxs(void)
{
int nr_ctxs;
mutex_lock(&damon_lock);
nr_ctxs = nr_running_ctxs;
mutex_unlock(&damon_lock);
return nr_ctxs;
}
/* Returns the size upper limit for each monitoring region */
static unsigned long damon_region_sz_limit(struct damon_ctx *ctx)
{
struct damon_target *t;
struct damon_region *r;
unsigned long sz = 0;
damon_for_each_target(t, ctx) {
damon_for_each_region(r, t)
sz += damon_sz_region(r);
}
if (ctx->attrs.min_nr_regions)
sz /= ctx->attrs.min_nr_regions;
if (sz < DAMON_MIN_REGION)
sz = DAMON_MIN_REGION;
return sz;
}
static int kdamond_fn(void *data);
/*
* __damon_start() - Starts monitoring with given context.
* @ctx: monitoring context
*
* This function should be called while damon_lock is hold.
*
* Return: 0 on success, negative error code otherwise.
*/
static int __damon_start(struct damon_ctx *ctx)
{
int err = -EBUSY;
mutex_lock(&ctx->kdamond_lock);
if (!ctx->kdamond) {
err = 0;
reinit_completion(&ctx->kdamond_started);
ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
nr_running_ctxs);
if (IS_ERR(ctx->kdamond)) {
err = PTR_ERR(ctx->kdamond);
ctx->kdamond = NULL;
} else {
wait_for_completion(&ctx->kdamond_started);
}
}
mutex_unlock(&ctx->kdamond_lock);
return err;
}
/**
* damon_start() - Starts the monitorings for a given group of contexts.
* @ctxs: an array of the pointers for contexts to start monitoring
* @nr_ctxs: size of @ctxs
* @exclusive: exclusiveness of this contexts group
*
* This function starts a group of monitoring threads for a group of monitoring
* contexts. One thread per each context is created and run in parallel. The
* caller should handle synchronization between the threads by itself. If
* @exclusive is true and a group of threads that created by other
* 'damon_start()' call is currently running, this function does nothing but
* returns -EBUSY.
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive)
{
int i;
int err = 0;
mutex_lock(&damon_lock);
if ((exclusive && nr_running_ctxs) ||
(!exclusive && running_exclusive_ctxs)) {
mutex_unlock(&damon_lock);
return -EBUSY;
}
for (i = 0; i < nr_ctxs; i++) {
err = __damon_start(ctxs[i]);
if (err)
break;
nr_running_ctxs++;
}
if (exclusive && nr_running_ctxs)
running_exclusive_ctxs = true;
mutex_unlock(&damon_lock);
return err;
}
/*
* __damon_stop() - Stops monitoring of a given context.
* @ctx: monitoring context
*
* Return: 0 on success, negative error code otherwise.
*/
static int __damon_stop(struct damon_ctx *ctx)
{
struct task_struct *tsk;
mutex_lock(&ctx->kdamond_lock);
tsk = ctx->kdamond;
if (tsk) {
get_task_struct(tsk);
mutex_unlock(&ctx->kdamond_lock);
kthread_stop_put(tsk);
return 0;
}
mutex_unlock(&ctx->kdamond_lock);
return -EPERM;
}
/**
* damon_stop() - Stops the monitorings for a given group of contexts.
* @ctxs: an array of the pointers for contexts to stop monitoring
* @nr_ctxs: size of @ctxs
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_stop(struct damon_ctx **ctxs, int nr_ctxs)
{
int i, err = 0;
for (i = 0; i < nr_ctxs; i++) {
/* nr_running_ctxs is decremented in kdamond_fn */
err = __damon_stop(ctxs[i]);
if (err)
break;
}
return err;
}
/*
* Reset the aggregated monitoring results ('nr_accesses' of each region).
*/
static void kdamond_reset_aggregated(struct damon_ctx *c)
{
struct damon_target *t;
unsigned int ti = 0; /* target's index */
damon_for_each_target(t, c) {
struct damon_region *r;
damon_for_each_region(r, t) {
trace_damon_aggregated(ti, r, damon_nr_regions(t));
r->last_nr_accesses = r->nr_accesses;
r->nr_accesses = 0;
}
ti++;
}
}
static void damon_split_region_at(struct damon_target *t,
struct damon_region *r, unsigned long sz_r);
static bool __damos_valid_target(struct damon_region *r, struct damos *s)
{
unsigned long sz;
unsigned int nr_accesses = r->nr_accesses_bp / 10000;
sz = damon_sz_region(r);
return s->pattern.min_sz_region <= sz &&
sz <= s->pattern.max_sz_region &&
s->pattern.min_nr_accesses <= nr_accesses &&
nr_accesses <= s->pattern.max_nr_accesses &&
s->pattern.min_age_region <= r->age &&
r->age <= s->pattern.max_age_region;
}
static bool damos_valid_target(struct damon_ctx *c, struct damon_target *t,
struct damon_region *r, struct damos *s)
{
bool ret = __damos_valid_target(r, s);
if (!ret || !s->quota.esz || !c->ops.get_scheme_score)
return ret;
return c->ops.get_scheme_score(c, t, r, s) >= s->quota.min_score;
}
/*
* damos_skip_charged_region() - Check if the given region or starting part of
* it is already charged for the DAMOS quota.
* @t: The target of the region.
* @rp: The pointer to the region.
* @s: The scheme to be applied.
*
* If a quota of a scheme has exceeded in a quota charge window, the scheme's
* action would applied to only a part of the target access pattern fulfilling
* regions. To avoid applying the scheme action to only already applied
* regions, DAMON skips applying the scheme action to the regions that charged
* in the previous charge window.
*
* This function checks if a given region should be skipped or not for the
* reason. If only the starting part of the region has previously charged,
* this function splits the region into two so that the second one covers the
* area that not charged in the previous charge widnow and saves the second
* region in *rp and returns false, so that the caller can apply DAMON action
* to the second one.
*
* Return: true if the region should be entirely skipped, false otherwise.
*/
static bool damos_skip_charged_region(struct damon_target *t,
struct damon_region **rp, struct damos *s)
{
struct damon_region *r = *rp;
struct damos_quota *quota = &s->quota;
unsigned long sz_to_skip;
/* Skip previously charged regions */
if (quota->charge_target_from) {
if (t != quota->charge_target_from)
return true;
if (r == damon_last_region(t)) {
quota->charge_target_from = NULL;
quota->charge_addr_from = 0;
return true;
}
if (quota->charge_addr_from &&
r->ar.end <= quota->charge_addr_from)
return true;
if (quota->charge_addr_from && r->ar.start <
quota->charge_addr_from) {
sz_to_skip = ALIGN_DOWN(quota->charge_addr_from -
r->ar.start, DAMON_MIN_REGION);
if (!sz_to_skip) {
if (damon_sz_region(r) <= DAMON_MIN_REGION)
return true;
sz_to_skip = DAMON_MIN_REGION;
}
damon_split_region_at(t, r, sz_to_skip);
r = damon_next_region(r);
*rp = r;
}
quota->charge_target_from = NULL;
quota->charge_addr_from = 0;
}
return false;
}
static void damos_update_stat(struct damos *s,
unsigned long sz_tried, unsigned long sz_applied)
{
s->stat.nr_tried++;
s->stat.sz_tried += sz_tried;
if (sz_applied)
s->stat.nr_applied++;
s->stat.sz_applied += sz_applied;
}
static bool __damos_filter_out(struct damon_ctx *ctx, struct damon_target *t,
struct damon_region *r, struct damos_filter *filter)
{
bool matched = false;
struct damon_target *ti;
int target_idx = 0;
unsigned long start, end;
switch (filter->type) {
case DAMOS_FILTER_TYPE_TARGET:
damon_for_each_target(ti, ctx) {
if (ti == t)
break;
target_idx++;
}
matched = target_idx == filter->target_idx;
break;
case DAMOS_FILTER_TYPE_ADDR:
start = ALIGN_DOWN(filter->addr_range.start, DAMON_MIN_REGION);
end = ALIGN_DOWN(filter->addr_range.end, DAMON_MIN_REGION);
/* inside the range */
if (start <= r->ar.start && r->ar.end <= end) {
matched = true;
break;
}
/* outside of the range */
if (r->ar.end <= start || end <= r->ar.start) {
matched = false;
break;
}
/* start before the range and overlap */
if (r->ar.start < start) {
damon_split_region_at(t, r, start - r->ar.start);
matched = false;
break;
}
/* start inside the range */
damon_split_region_at(t, r, end - r->ar.start);
matched = true;
break;
default:
return false;
}
return matched == filter->matching;
}
static bool damos_filter_out(struct damon_ctx *ctx, struct damon_target *t,
struct damon_region *r, struct damos *s)
{
struct damos_filter *filter;
damos_for_each_filter(filter, s) {
if (__damos_filter_out(ctx, t, r, filter))
return true;
}
return false;
}
static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
struct damon_region *r, struct damos *s)
{
struct damos_quota *quota = &s->quota;
unsigned long sz = damon_sz_region(r);
struct timespec64 begin, end;
unsigned long sz_applied = 0;
int err = 0;
/*
* We plan to support multiple context per kdamond, as DAMON sysfs
* implies with 'nr_contexts' file. Nevertheless, only single context
* per kdamond is supported for now. So, we can simply use '0' context
* index here.
*/
unsigned int cidx = 0;
struct damos *siter; /* schemes iterator */
unsigned int sidx = 0;
struct damon_target *titer; /* targets iterator */
unsigned int tidx = 0;
bool do_trace = false;
/* get indices for trace_damos_before_apply() */
if (trace_damos_before_apply_enabled()) {
damon_for_each_scheme(siter, c) {
if (siter == s)
break;
sidx++;
}
damon_for_each_target(titer, c) {
if (titer == t)
break;
tidx++;
}
do_trace = true;
}
if (c->ops.apply_scheme) {
if (quota->esz && quota->charged_sz + sz > quota->esz) {
sz = ALIGN_DOWN(quota->esz - quota->charged_sz,
DAMON_MIN_REGION);
if (!sz)
goto update_stat;
damon_split_region_at(t, r, sz);
}
if (damos_filter_out(c, t, r, s))
return;
ktime_get_coarse_ts64(&begin);
if (c->callback.before_damos_apply)
err = c->callback.before_damos_apply(c, t, r, s);
if (!err) {
trace_damos_before_apply(cidx, sidx, tidx, r,
damon_nr_regions(t), do_trace);
sz_applied = c->ops.apply_scheme(c, t, r, s);
}
ktime_get_coarse_ts64(&end);
quota->total_charged_ns += timespec64_to_ns(&end) -
timespec64_to_ns(&begin);
quota->charged_sz += sz;
if (quota->esz && quota->charged_sz >= quota->esz) {
quota->charge_target_from = t;
quota->charge_addr_from = r->ar.end + 1;
}
}
if (s->action != DAMOS_STAT)
r->age = 0;
update_stat:
damos_update_stat(s, sz, sz_applied);
}
static void damon_do_apply_schemes(struct damon_ctx *c,
struct damon_target *t,
struct damon_region *r)
{
struct damos *s;
damon_for_each_scheme(s, c) {
struct damos_quota *quota = &s->quota;
if (c->passed_sample_intervals != s->next_apply_sis)
continue;
if (!s->wmarks.activated)
continue;
/* Check the quota */
if (quota->esz && quota->charged_sz >= quota->esz)
continue;
if (damos_skip_charged_region(t, &r, s))
continue;
if (!damos_valid_target(c, t, r, s))
continue;
damos_apply_scheme(c, t, r, s);
}
}
/*
* damon_feed_loop_next_input() - get next input to achieve a target score.
* @last_input The last input.
* @score Current score that made with @last_input.
*
* Calculate next input to achieve the target score, based on the last input
* and current score. Assuming the input and the score are positively
* proportional, calculate how much compensation should be added to or
* subtracted from the last input as a proportion of the last input. Avoid
* next input always being zero by setting it non-zero always. In short form
* (assuming support of float and signed calculations), the algorithm is as
* below.
*
* next_input = max(last_input * ((goal - current) / goal + 1), 1)
*
* For simple implementation, we assume the target score is always 10,000. The
* caller should adjust @score for this.
*
* Returns next input that assumed to achieve the target score.
*/
static unsigned long damon_feed_loop_next_input(unsigned long last_input,
unsigned long score)
{
const unsigned long goal = 10000;
unsigned long score_goal_diff = max(goal, score) - min(goal, score);
unsigned long score_goal_diff_bp = score_goal_diff * 10000 / goal;
unsigned long compensation = last_input * score_goal_diff_bp / 10000;
/* Set minimum input as 10000 to avoid compensation be zero */
const unsigned long min_input = 10000;
if (goal > score)
return last_input + compensation;
if (last_input > compensation + min_input)
return last_input - compensation;
return min_input;
}
#ifdef CONFIG_PSI
static u64 damos_get_some_mem_psi_total(void)
{
if (static_branch_likely(&psi_disabled))
return 0;
return div_u64(psi_system.total[PSI_AVGS][PSI_MEM * 2],
NSEC_PER_USEC);
}
#else /* CONFIG_PSI */
static inline u64 damos_get_some_mem_psi_total(void)
{
return 0;
};
#endif /* CONFIG_PSI */
static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
{
u64 now_psi_total;
switch (goal->metric) {
case DAMOS_QUOTA_USER_INPUT:
/* User should already set goal->current_value */
break;
case DAMOS_QUOTA_SOME_MEM_PSI_US:
now_psi_total = damos_get_some_mem_psi_total();
goal->current_value = now_psi_total - goal->last_psi_total;
goal->last_psi_total = now_psi_total;
break;
default:
break;
}
}
/* Return the highest score since it makes schemes least aggressive */
static unsigned long damos_quota_score(struct damos_quota *quota)
{
struct damos_quota_goal *goal;
unsigned long highest_score = 0;
damos_for_each_quota_goal(goal, quota) {
damos_set_quota_goal_current_value(goal);
highest_score = max(highest_score,
goal->current_value * 10000 /
goal->target_value);
}
return highest_score;
}
/*
* Called only if quota->ms, or quota->sz are set, or quota->goals is not empty
*/
static void damos_set_effective_quota(struct damos_quota *quota)
{
unsigned long throughput;
unsigned long esz;
if (!quota->ms && list_empty(&quota->goals)) {
quota->esz = quota->sz;
return;
}
if (!list_empty(&quota->goals)) {
unsigned long score = damos_quota_score(quota);
quota->esz_bp = damon_feed_loop_next_input(
max(quota->esz_bp, 10000UL),
score);
esz = quota->esz_bp / 10000;
}
if (quota->ms) {
if (quota->total_charged_ns)
throughput = quota->total_charged_sz * 1000000 /
quota->total_charged_ns;
else
throughput = PAGE_SIZE * 1024;
if (!list_empty(&quota->goals))
esz = min(throughput * quota->ms, esz);
else
esz = throughput * quota->ms;
}
if (quota->sz && quota->sz < esz)
esz = quota->sz;
quota->esz = esz;
}
static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
{
struct damos_quota *quota = &s->quota;
struct damon_target *t;
struct damon_region *r;
unsigned long cumulated_sz;
unsigned int score, max_score = 0;
if (!quota->ms && !quota->sz && list_empty(&quota->goals))
return;
/* New charge window starts */
if (time_after_eq(jiffies, quota->charged_from +
msecs_to_jiffies(quota->reset_interval))) {
if (quota->esz && quota->charged_sz >= quota->esz)
s->stat.qt_exceeds++;
quota->total_charged_sz += quota->charged_sz;
quota->charged_from = jiffies;
quota->charged_sz = 0;
damos_set_effective_quota(quota);
}
if (!c->ops.get_scheme_score)
return;
/* Fill up the score histogram */
memset(quota->histogram, 0, sizeof(quota->histogram));
damon_for_each_target(t, c) {
damon_for_each_region(r, t) {
if (!__damos_valid_target(r, s))
continue;
score = c->ops.get_scheme_score(c, t, r, s);
quota->histogram[score] += damon_sz_region(r);
if (score > max_score)
max_score = score;
}
}
/* Set the min score limit */
for (cumulated_sz = 0, score = max_score; ; score--) {
cumulated_sz += quota->histogram[score];
if (cumulated_sz >= quota->esz || !score)
break;
}
quota->min_score = score;
}
static void kdamond_apply_schemes(struct damon_ctx *c)
{
struct damon_target *t;
struct damon_region *r, *next_r;
struct damos *s;
unsigned long sample_interval = c->attrs.sample_interval ?
c->attrs.sample_interval : 1;
bool has_schemes_to_apply = false;
damon_for_each_scheme(s, c) {
if (c->passed_sample_intervals != s->next_apply_sis)
continue;
if (!s->wmarks.activated)
continue;
has_schemes_to_apply = true;
damos_adjust_quota(c, s);
}
if (!has_schemes_to_apply)
return;
damon_for_each_target(t, c) {
damon_for_each_region_safe(r, next_r, t)
damon_do_apply_schemes(c, t, r);
}
damon_for_each_scheme(s, c) {
if (c->passed_sample_intervals != s->next_apply_sis)
continue;
s->next_apply_sis +=
(s->apply_interval_us ? s->apply_interval_us :
c->attrs.aggr_interval) / sample_interval;
}
}
/*
* Merge two adjacent regions into one region
*/
static void damon_merge_two_regions(struct damon_target *t,
struct damon_region *l, struct damon_region *r)
{
unsigned long sz_l = damon_sz_region(l), sz_r = damon_sz_region(r);
l->nr_accesses = (l->nr_accesses * sz_l + r->nr_accesses * sz_r) /
(sz_l + sz_r);
l->nr_accesses_bp = l->nr_accesses * 10000;
l->age = (l->age * sz_l + r->age * sz_r) / (sz_l + sz_r);
l->ar.end = r->ar.end;
damon_destroy_region(r, t);
}
/*
* Merge adjacent regions having similar access frequencies
*
* t target affected by this merge operation
* thres '->nr_accesses' diff threshold for the merge
* sz_limit size upper limit of each region
*/
static void damon_merge_regions_of(struct damon_target *t, unsigned int thres,
unsigned long sz_limit)
{
struct damon_region *r, *prev = NULL, *next;
damon_for_each_region_safe(r, next, t) {
if (abs(r->nr_accesses - r->last_nr_accesses) > thres)
r->age = 0;
else
r->age++;
if (prev && prev->ar.end == r->ar.start &&
abs(prev->nr_accesses - r->nr_accesses) <= thres &&
damon_sz_region(prev) + damon_sz_region(r) <= sz_limit)
damon_merge_two_regions(t, prev, r);
else
prev = r;
}
}
/*
* Merge adjacent regions having similar access frequencies
*
* threshold '->nr_accesses' diff threshold for the merge
* sz_limit size upper limit of each region
*
* This function merges monitoring target regions which are adjacent and their
* access frequencies are similar. This is for minimizing the monitoring
* overhead under the dynamically changeable access pattern. If a merge was
* unnecessarily made, later 'kdamond_split_regions()' will revert it.
*/
static void kdamond_merge_regions(struct damon_ctx *c, unsigned int threshold,
unsigned long sz_limit)
{
struct damon_target *t;
damon_for_each_target(t, c)
damon_merge_regions_of(t, threshold, sz_limit);
}
/*
* Split a region in two
*
* r the region to be split
* sz_r size of the first sub-region that will be made
*/
static void damon_split_region_at(struct damon_target *t,
struct damon_region *r, unsigned long sz_r)
{
struct damon_region *new;
new = damon_new_region(r->ar.start + sz_r, r->ar.end);
if (!new)
return;
r->ar.end = new->ar.start;
new->age = r->age;
new->last_nr_accesses = r->last_nr_accesses;
new->nr_accesses_bp = r->nr_accesses_bp;
new->nr_accesses = r->nr_accesses;
damon_insert_region(new, r, damon_next_region(r), t);
}
/* Split every region in the given target into 'nr_subs' regions */
static void damon_split_regions_of(struct damon_target *t, int nr_subs)
{
struct damon_region *r, *next;
unsigned long sz_region, sz_sub = 0;
int i;
damon_for_each_region_safe(r, next, t) {
sz_region = damon_sz_region(r);
for (i = 0; i < nr_subs - 1 &&
sz_region > 2 * DAMON_MIN_REGION; i++) {
/*
* Randomly select size of left sub-region to be at
* least 10 percent and at most 90% of original region
*/
sz_sub = ALIGN_DOWN(damon_rand(1, 10) *
sz_region / 10, DAMON_MIN_REGION);
/* Do not allow blank region */
if (sz_sub == 0 || sz_sub >= sz_region)
continue;
damon_split_region_at(t, r, sz_sub);
sz_region = sz_sub;
}
}
}
/*
* Split every target region into randomly-sized small regions
*
* This function splits every target region into random-sized small regions if
* current total number of the regions is equal or smaller than half of the
* user-specified maximum number of regions. This is for maximizing the
* monitoring accuracy under the dynamically changeable access patterns. If a
* split was unnecessarily made, later 'kdamond_merge_regions()' will revert
* it.
*/
static void kdamond_split_regions(struct damon_ctx *ctx)
{
struct damon_target *t;
unsigned int nr_regions = 0;
static unsigned int last_nr_regions;
int nr_subregions = 2;
damon_for_each_target(t, ctx)
nr_regions += damon_nr_regions(t);
if (nr_regions > ctx->attrs.max_nr_regions / 2)
return;
/* Maybe the middle of the region has different access frequency */
if (last_nr_regions == nr_regions &&
nr_regions < ctx->attrs.max_nr_regions / 3)
nr_subregions = 3;
damon_for_each_target(t, ctx)
damon_split_regions_of(t, nr_subregions);
last_nr_regions = nr_regions;
}
/*
* Check whether current monitoring should be stopped
*
* The monitoring is stopped when either the user requested to stop, or all
* monitoring targets are invalid.
*
* Returns true if need to stop current monitoring.
*/
static bool kdamond_need_stop(struct damon_ctx *ctx)
{
struct damon_target *t;
if (kthread_should_stop())
return true;
if (!ctx->ops.target_valid)
return false;
damon_for_each_target(t, ctx) {
if (ctx->ops.target_valid(t))
return false;
}
return true;
}
static int damos_get_wmark_metric_value(enum damos_wmark_metric metric,
unsigned long *metric_value)
{
switch (metric) {
case DAMOS_WMARK_FREE_MEM_RATE:
*metric_value = global_zone_page_state(NR_FREE_PAGES) * 1000 /
totalram_pages();
return 0;
default:
break;
}
return -EINVAL;
}
/*
* Returns zero if the scheme is active. Else, returns time to wait for next
* watermark check in micro-seconds.
*/
static unsigned long damos_wmark_wait_us(struct damos *scheme)
{
unsigned long metric;
if (damos_get_wmark_metric_value(scheme->wmarks.metric, &metric))
return 0;
/* higher than high watermark or lower than low watermark */
if (metric > scheme->wmarks.high || scheme->wmarks.low > metric) {
if (scheme->wmarks.activated)
pr_debug("deactivate a scheme (%d) for %s wmark\n",
scheme->action,
metric > scheme->wmarks.high ?
"high" : "low");
scheme->wmarks.activated = false;
return scheme->wmarks.interval;
}
/* inactive and higher than middle watermark */
if ((scheme->wmarks.high >= metric && metric >= scheme->wmarks.mid) &&
!scheme->wmarks.activated)
return scheme->wmarks.interval;
if (!scheme->wmarks.activated)
pr_debug("activate a scheme (%d)\n", scheme->action);
scheme->wmarks.activated = true;
return 0;
}
static void kdamond_usleep(unsigned long usecs)
{
/* See Documentation/timers/timers-howto.rst for the thresholds */
if (usecs > 20 * USEC_PER_MSEC)
schedule_timeout_idle(usecs_to_jiffies(usecs));
else
usleep_idle_range(usecs, usecs + 1);
}
/* Returns negative error code if it's not activated but should return */
static int kdamond_wait_activation(struct damon_ctx *ctx)
{
struct damos *s;
unsigned long wait_time;
unsigned long min_wait_time = 0;
bool init_wait_time = false;
while (!kdamond_need_stop(ctx)) {
damon_for_each_scheme(s, ctx) {
wait_time = damos_wmark_wait_us(s);
if (!init_wait_time || wait_time < min_wait_time) {
init_wait_time = true;
min_wait_time = wait_time;
}
}
if (!min_wait_time)
return 0;
kdamond_usleep(min_wait_time);
if (ctx->callback.after_wmarks_check &&
ctx->callback.after_wmarks_check(ctx))
break;
}
return -EBUSY;
}
static void kdamond_init_intervals_sis(struct damon_ctx *ctx)
{
unsigned long sample_interval = ctx->attrs.sample_interval ?
ctx->attrs.sample_interval : 1;
unsigned long apply_interval;
struct damos *scheme;
ctx->passed_sample_intervals = 0;
ctx->next_aggregation_sis = ctx->attrs.aggr_interval / sample_interval;
ctx->next_ops_update_sis = ctx->attrs.ops_update_interval /
sample_interval;
damon_for_each_scheme(scheme, ctx) {
apply_interval = scheme->apply_interval_us ?
scheme->apply_interval_us : ctx->attrs.aggr_interval;
scheme->next_apply_sis = apply_interval / sample_interval;
}
}
/*
* The monitoring daemon that runs as a kernel thread
*/
static int kdamond_fn(void *data)
{
struct damon_ctx *ctx = data;
struct damon_target *t;
struct damon_region *r, *next;
unsigned int max_nr_accesses = 0;
unsigned long sz_limit = 0;
pr_debug("kdamond (%d) starts\n", current->pid);
complete(&ctx->kdamond_started);
kdamond_init_intervals_sis(ctx);
if (ctx->ops.init)
ctx->ops.init(ctx);
if (ctx->callback.before_start && ctx->callback.before_start(ctx))
goto done;
sz_limit = damon_region_sz_limit(ctx);
while (!kdamond_need_stop(ctx)) {
/*
* ctx->attrs and ctx->next_{aggregation,ops_update}_sis could
* be changed from after_wmarks_check() or after_aggregation()
* callbacks. Read the values here, and use those for this
* iteration. That is, damon_set_attrs() updated new values
* are respected from next iteration.
*/
unsigned long next_aggregation_sis = ctx->next_aggregation_sis;
unsigned long next_ops_update_sis = ctx->next_ops_update_sis;
unsigned long sample_interval = ctx->attrs.sample_interval;
if (kdamond_wait_activation(ctx))
break;
if (ctx->ops.prepare_access_checks)
ctx->ops.prepare_access_checks(ctx);
if (ctx->callback.after_sampling &&
ctx->callback.after_sampling(ctx))
break;
kdamond_usleep(sample_interval);
ctx->passed_sample_intervals++;
if (ctx->ops.check_accesses)
max_nr_accesses = ctx->ops.check_accesses(ctx);
if (ctx->passed_sample_intervals == next_aggregation_sis) {
kdamond_merge_regions(ctx,
max_nr_accesses / 10,
sz_limit);
if (ctx->callback.after_aggregation &&
ctx->callback.after_aggregation(ctx))
break;
}
/*
* do kdamond_apply_schemes() after kdamond_merge_regions() if
* possible, to reduce overhead
*/
if (!list_empty(&ctx->schemes))
kdamond_apply_schemes(ctx);
sample_interval = ctx->attrs.sample_interval ?
ctx->attrs.sample_interval : 1;
if (ctx->passed_sample_intervals == next_aggregation_sis) {
ctx->next_aggregation_sis = next_aggregation_sis +
ctx->attrs.aggr_interval / sample_interval;
kdamond_reset_aggregated(ctx);
kdamond_split_regions(ctx);
if (ctx->ops.reset_aggregated)
ctx->ops.reset_aggregated(ctx);
}
if (ctx->passed_sample_intervals == next_ops_update_sis) {
ctx->next_ops_update_sis = next_ops_update_sis +
ctx->attrs.ops_update_interval /
sample_interval;
if (ctx->ops.update)
ctx->ops.update(ctx);
sz_limit = damon_region_sz_limit(ctx);
}
}
done:
damon_for_each_target(t, ctx) {
damon_for_each_region_safe(r, next, t)
damon_destroy_region(r, t);
}
if (ctx->callback.before_terminate)
ctx->callback.before_terminate(ctx);
if (ctx->ops.cleanup)
ctx->ops.cleanup(ctx);
pr_debug("kdamond (%d) finishes\n", current->pid);
mutex_lock(&ctx->kdamond_lock);
ctx->kdamond = NULL;
mutex_unlock(&ctx->kdamond_lock);
mutex_lock(&damon_lock);
nr_running_ctxs--;
if (!nr_running_ctxs && running_exclusive_ctxs)
running_exclusive_ctxs = false;
mutex_unlock(&damon_lock);
return 0;
}
/*
* struct damon_system_ram_region - System RAM resource address region of
* [@start, @end).
* @start: Start address of the region (inclusive).
* @end: End address of the region (exclusive).
*/
struct damon_system_ram_region {
unsigned long start;
unsigned long end;
};
static int walk_system_ram(struct resource *res, void *arg)
{
struct damon_system_ram_region *a = arg;
if (a->end - a->start < resource_size(res)) {
a->start = res->start;
a->end = res->end;
}
return 0;
}
/*
* Find biggest 'System RAM' resource and store its start and end address in
* @start and @end, respectively. If no System RAM is found, returns false.
*/
static bool damon_find_biggest_system_ram(unsigned long *start,
unsigned long *end)
{
struct damon_system_ram_region arg = {};
walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
if (arg.end <= arg.start)
return false;
*start = arg.start;
*end = arg.end;
return true;
}
/**
* damon_set_region_biggest_system_ram_default() - Set the region of the given
* monitoring target as requested, or biggest 'System RAM'.
* @t: The monitoring target to set the region.
* @start: The pointer to the start address of the region.
* @end: The pointer to the end address of the region.
*
* This function sets the region of @t as requested by @start and @end. If the
* values of @start and @end are zero, however, this function finds the biggest
* 'System RAM' resource and sets the region to cover the resource. In the
* latter case, this function saves the start and end addresses of the resource
* in @start and @end, respectively.
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_set_region_biggest_system_ram_default(struct damon_target *t,
unsigned long *start, unsigned long *end)
{
struct damon_addr_range addr_range;
if (*start > *end)
return -EINVAL;
if (!*start && !*end &&
!damon_find_biggest_system_ram(start, end))
return -EINVAL;
addr_range.start = *start;
addr_range.end = *end;
return damon_set_regions(t, &addr_range, 1);
}
/*
* damon_moving_sum() - Calculate an inferred moving sum value.
* @mvsum: Inferred sum of the last @len_window values.
* @nomvsum: Non-moving sum of the last discrete @len_window window values.
* @len_window: The number of last values to take care of.
* @new_value: New value that will be added to the pseudo moving sum.
*
* Moving sum (moving average * window size) is good for handling noise, but
* the cost of keeping past values can be high for arbitrary window size. This
* function implements a lightweight pseudo moving sum function that doesn't
* keep the past window values.
*
* It simply assumes there was no noise in the past, and get the no-noise
* assumed past value to drop from @nomvsum and @len_window. @nomvsum is a
* non-moving sum of the last window. For example, if @len_window is 10 and we
* have 25 values, @nomvsum is the sum of the 11th to 20th values of the 25
* values. Hence, this function simply drops @nomvsum / @len_window from
* given @mvsum and add @new_value.
*
* For example, if @len_window is 10 and @nomvsum is 50, the last 10 values for
* the last window could be vary, e.g., 0, 10, 0, 10, 0, 10, 0, 0, 0, 20. For
* calculating next moving sum with a new value, we should drop 0 from 50 and
* add the new value. However, this function assumes it got value 5 for each
* of the last ten times. Based on the assumption, when the next value is
* measured, it drops the assumed past value, 5 from the current sum, and add
* the new value to get the updated pseduo-moving average.
*
* This means the value could have errors, but the errors will be disappeared
* for every @len_window aligned calls. For example, if @len_window is 10, the
* pseudo moving sum with 11th value to 19th value would have an error. But
* the sum with 20th value will not have the error.
*
* Return: Pseudo-moving average after getting the @new_value.
*/
static unsigned int damon_moving_sum(unsigned int mvsum, unsigned int nomvsum,
unsigned int len_window, unsigned int new_value)
{
return mvsum - nomvsum / len_window + new_value;
}
/**
* damon_update_region_access_rate() - Update the access rate of a region.
* @r: The DAMON region to update for its access check result.
* @accessed: Whether the region has accessed during last sampling interval.
* @attrs: The damon_attrs of the DAMON context.
*
* Update the access rate of a region with the region's last sampling interval
* access check result.
*
* Usually this will be called by &damon_operations->check_accesses callback.
*/
void damon_update_region_access_rate(struct damon_region *r, bool accessed,
struct damon_attrs *attrs)
{
unsigned int len_window = 1;
/*
* sample_interval can be zero, but cannot be larger than
* aggr_interval, owing to validation of damon_set_attrs().
*/
if (attrs->sample_interval)
len_window = damon_max_nr_accesses(attrs);
r->nr_accesses_bp = damon_moving_sum(r->nr_accesses_bp,
r->last_nr_accesses * 10000, len_window,
accessed ? 10000 : 0);
if (accessed)
r->nr_accesses++;
}
static int __init damon_init(void)
{
damon_region_cache = KMEM_CACHE(damon_region, 0);
if (unlikely(!damon_region_cache)) {
pr_err("creating damon_region_cache fails\n");
return -ENOMEM;
}
return 0;
}
subsys_initcall(damon_init);
#include "core-test.h"