| From 96628bd31e5bacf4fd6f015341a1e66e368e1f7c Mon Sep 17 00:00:00 2001 |
| From: Thomas Richter <tmricht@linux.ibm.com> |
| Date: Mon, 21 Oct 2019 10:33:54 +0200 |
| Subject: [PATCH] perf/aux: Fix tracking of auxiliary trace buffer allocation |
| |
| commit 5e6c3c7b1ec217c1c4c95d9148182302b9969b97 upstream. |
| |
| The following commit from the v5.4 merge window: |
| |
| d44248a41337 ("perf/core: Rework memory accounting in perf_mmap()") |
| |
| ... breaks auxiliary trace buffer tracking. |
| |
| If I run command 'perf record -e rbd000' to record samples and saving |
| them in the **auxiliary** trace buffer then the value of 'locked_vm' becomes |
| negative after all trace buffers have been allocated and released: |
| |
| During allocation the values increase: |
| |
| [52.250027] perf_mmap user->locked_vm:0x87 pinned_vm:0x0 ret:0 |
| [52.250115] perf_mmap user->locked_vm:0x107 pinned_vm:0x0 ret:0 |
| [52.250251] perf_mmap user->locked_vm:0x188 pinned_vm:0x0 ret:0 |
| [52.250326] perf_mmap user->locked_vm:0x208 pinned_vm:0x0 ret:0 |
| [52.250441] perf_mmap user->locked_vm:0x289 pinned_vm:0x0 ret:0 |
| [52.250498] perf_mmap user->locked_vm:0x309 pinned_vm:0x0 ret:0 |
| [52.250613] perf_mmap user->locked_vm:0x38a pinned_vm:0x0 ret:0 |
| [52.250715] perf_mmap user->locked_vm:0x408 pinned_vm:0x2 ret:0 |
| [52.250834] perf_mmap user->locked_vm:0x408 pinned_vm:0x83 ret:0 |
| [52.250915] perf_mmap user->locked_vm:0x408 pinned_vm:0x103 ret:0 |
| [52.251061] perf_mmap user->locked_vm:0x408 pinned_vm:0x184 ret:0 |
| [52.251146] perf_mmap user->locked_vm:0x408 pinned_vm:0x204 ret:0 |
| [52.251299] perf_mmap user->locked_vm:0x408 pinned_vm:0x285 ret:0 |
| [52.251383] perf_mmap user->locked_vm:0x408 pinned_vm:0x305 ret:0 |
| [52.251544] perf_mmap user->locked_vm:0x408 pinned_vm:0x386 ret:0 |
| [52.251634] perf_mmap user->locked_vm:0x408 pinned_vm:0x406 ret:0 |
| [52.253018] perf_mmap user->locked_vm:0x408 pinned_vm:0x487 ret:0 |
| [52.253197] perf_mmap user->locked_vm:0x408 pinned_vm:0x508 ret:0 |
| [52.253374] perf_mmap user->locked_vm:0x408 pinned_vm:0x589 ret:0 |
| [52.253550] perf_mmap user->locked_vm:0x408 pinned_vm:0x60a ret:0 |
| [52.253726] perf_mmap user->locked_vm:0x408 pinned_vm:0x68b ret:0 |
| [52.253903] perf_mmap user->locked_vm:0x408 pinned_vm:0x70c ret:0 |
| [52.254084] perf_mmap user->locked_vm:0x408 pinned_vm:0x78d ret:0 |
| [52.254263] perf_mmap user->locked_vm:0x408 pinned_vm:0x80e ret:0 |
| |
| The value of user->locked_vm increases to a limit then the memory |
| is tracked by pinned_vm. |
| |
| During deallocation the size is subtracted from pinned_vm until |
| it hits a limit. Then a larger value is subtracted from locked_vm |
| leading to a large number (because of type unsigned): |
| |
| [64.267797] perf_mmap_close mmap_user->locked_vm:0x408 pinned_vm:0x78d |
| [64.267826] perf_mmap_close mmap_user->locked_vm:0x408 pinned_vm:0x70c |
| [64.267848] perf_mmap_close mmap_user->locked_vm:0x408 pinned_vm:0x68b |
| [64.267869] perf_mmap_close mmap_user->locked_vm:0x408 pinned_vm:0x60a |
| [64.267891] perf_mmap_close mmap_user->locked_vm:0x408 pinned_vm:0x589 |
| [64.267911] perf_mmap_close mmap_user->locked_vm:0x408 pinned_vm:0x508 |
| [64.267933] perf_mmap_close mmap_user->locked_vm:0x408 pinned_vm:0x487 |
| [64.267952] perf_mmap_close mmap_user->locked_vm:0x408 pinned_vm:0x406 |
| [64.268883] perf_mmap_close mmap_user->locked_vm:0x307 pinned_vm:0x406 |
| [64.269117] perf_mmap_close mmap_user->locked_vm:0x206 pinned_vm:0x406 |
| [64.269433] perf_mmap_close mmap_user->locked_vm:0x105 pinned_vm:0x406 |
| [64.269536] perf_mmap_close mmap_user->locked_vm:0x4 pinned_vm:0x404 |
| [64.269797] perf_mmap_close mmap_user->locked_vm:0xffffffffffffff84 pinned_vm:0x303 |
| [64.270105] perf_mmap_close mmap_user->locked_vm:0xffffffffffffff04 pinned_vm:0x202 |
| [64.270374] perf_mmap_close mmap_user->locked_vm:0xfffffffffffffe84 pinned_vm:0x101 |
| [64.270628] perf_mmap_close mmap_user->locked_vm:0xfffffffffffffe04 pinned_vm:0x0 |
| |
| This value sticks for the user until system is rebooted, causing |
| follow-on system calls using locked_vm resource limit to fail. |
| |
| Note: There is no issue using the normal trace buffer. |
| |
| In fact the issue is in perf_mmap_close(). During allocation auxiliary |
| trace buffer memory is either traced as 'extra' and added to 'pinned_vm' |
| or trace as 'user_extra' and added to 'locked_vm'. This applies for |
| normal trace buffers and auxiliary trace buffer. |
| |
| However in function perf_mmap_close() all auxiliary trace buffer is |
| subtraced from 'locked_vm' and never from 'pinned_vm'. This breaks the |
| ballance. |
| |
| Signed-off-by: Thomas Richter <tmricht@linux.ibm.com> |
| Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> |
| Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> |
| Cc: Arnaldo Carvalho de Melo <acme@redhat.com> |
| Cc: Jiri Olsa <jolsa@redhat.com> |
| Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| Cc: Mark Rutland <mark.rutland@arm.com> |
| Cc: Namhyung Kim <namhyung@kernel.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Cc: acme@kernel.org |
| Cc: gor@linux.ibm.com |
| Cc: hechaol@fb.com |
| Cc: heiko.carstens@de.ibm.com |
| Cc: linux-perf-users@vger.kernel.org |
| Cc: songliubraving@fb.com |
| Fixes: d44248a41337 ("perf/core: Rework memory accounting in perf_mmap()") |
| Link: https://lkml.kernel.org/r/20191021083354.67868-1-tmricht@linux.ibm.com |
| [ Minor readability edits. ] |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/kernel/events/core.c b/kernel/events/core.c |
| index f8c223c70c32..1624c5a926ab 100644 |
| --- a/kernel/events/core.c |
| +++ b/kernel/events/core.c |
| @@ -5522,8 +5522,10 @@ static void perf_mmap_close(struct vm_area_struct *vma) |
| perf_pmu_output_stop(event); |
| |
| /* now it's safe to free the pages */ |
| - atomic_long_sub(rb->aux_nr_pages, &mmap_user->locked_vm); |
| - atomic64_sub(rb->aux_mmap_locked, &vma->vm_mm->pinned_vm); |
| + if (!rb->aux_mmap_locked) |
| + atomic_long_sub(rb->aux_nr_pages, &mmap_user->locked_vm); |
| + else |
| + atomic64_sub(rb->aux_mmap_locked, &vma->vm_mm->pinned_vm); |
| |
| /* this has to be the last one */ |
| rb_free_aux(rb); |
| -- |
| 2.7.4 |
| |