update FIFO boosting scheme (v3)
Fix incorrect policy in boost_with_fifo (cut-n-paste error).
Update error handling and behavior if unable to change policies so
that daemon runs in logging only mode.
Temporarily changed dl runtime during check_policies so that deadline
runtime is half of period. Restore after successfull boost.
Signed-off-by: Clark Williams <williams@redhat.com>
diff --git a/src/stalld.c b/src/stalld.c
index f0722bc..f6a85af 100644
--- a/src/stalld.c
+++ b/src/stalld.c
@@ -143,7 +143,7 @@
/*
* boolean to choose between deadline and fifo
*/
-int use_deadline;
+int boost_policy;
/*
* print any error messages and exit
@@ -742,13 +742,13 @@
memset(&attr, 0, sizeof(attr));
attr.size = sizeof(attr);
- attr.sched_policy = SCHED_DEADLINE;
+ attr.sched_policy = SCHED_FIFO;
attr.sched_priority = config_fifo_priority;
ret = sched_setattr(pid, &attr, flags);
if (ret < 0) {
log_msg("boost_with_fifo failed to boost pid %d: %s\n", pid, strerror(errno));
- return 1;
+ return ret;
}
return ret;
}
@@ -828,7 +828,7 @@
/*
* Boost.
*/
- if (use_deadline) {
+ if (boost_policy == SCHED_DEADLINE) {
ret = boost_with_deadline(pid);
if (ret < 0)
return ret;
@@ -1267,9 +1267,11 @@
}
-int check_for_deadline(void)
+int check_policies(void)
{
int ret;
+ int saved_runtime = config_dl_runtime;
+ int boosted = SCHED_DEADLINE;
struct sched_attr attr;
/*
@@ -1278,18 +1280,45 @@
*/
if (config_force_fifo) {
log_msg("forcing SCHED_FIFO for boosting\n");
- return 0;
+ return SCHED_FIFO;
}
+ // set runtime to half of period
+ config_dl_runtime = config_dl_period / 2;
+
+ // save off the current policy
if (get_current_policy(0, &attr))
- die("check_for_deadline: unable to get scheduling policy!");
- ret = boost_with_deadline(0) == 0 ? 1 : 0;
- restore_policy(0, &attr);
- if (ret)
+ die("check_policies: unable to get scheduling policy!");
+
+ // try boosting to SCHED_DEADLINE
+ ret = boost_with_deadline(0);
+ if (ret < 0) {
+ // try boosting with fifo to see if we have permission
+ ret = boost_with_fifo(0);
+ if (ret < 0) {
+ log_msg("check_policies: unable to change policy to either deadline or fifo,"
+ "defaulting to logging only\n");
+ config_log_only = 1;
+ boosted = 0;
+ }
+ else
+ boosted = SCHED_FIFO;
+ }
+ // if we successfully boosted to something, restore the old policy
+ if (boosted) {
+ ret = restore_policy(0, &attr);
+ // if we can't restore the policy then quit now
+ if (ret < 0)
+ die("check_policies: unable to restore policy: %s\n", strerror(errno));
+ }
+
+ // restore the actual runtime value
+ config_dl_runtime = saved_runtime;
+ if (boosted == SCHED_DEADLINE)
log_msg("using SCHED_DEADLINE for boosting\n");
- else
+ else if (boosted == SCHED_FIFO)
log_msg("using SCHED_FIFO for boosting\n");
- return ret;
+ return boosted;
}
int main(int argc, char **argv)
@@ -1302,7 +1331,7 @@
/*
* see if deadline scheduler is available
*/
- use_deadline = check_for_deadline();
+ boost_policy = check_policies();
nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
if (nr_cpus < 1)
