| Message ID | 20231120084300.4368-1-osalvador@suse.de (mailing list archive) |
|---|---|
| Headers | show |
| Series | page_owner: print stacks and their counter | expand |
On 11/20/23 09:42, Oscar Salvador wrote: > Changes v5 -> v6: > - Rebase on top of v6.7-rc1 Hi, I think at this point it would be better to rebase on top of https://lore.kernel.org/all/cover.1698077459.git.andreyknvl@google.com/ which already contains the refcount field in stack_record. (and maybe help with the review of that series as well? Hopefully it can get to mm/unstable and -next towards 6.8 soon :) Vlastimil
On Mon, Nov 20, 2023 at 10:07 AM Vlastimil Babka <vbabka@suse.cz> wrote: > > On 11/20/23 09:42, Oscar Salvador wrote: > > Changes v5 -> v6: > > - Rebase on top of v6.7-rc1 > > Hi, > > I think at this point it would be better to rebase on top of > https://lore.kernel.org/all/cover.1698077459.git.andreyknvl@google.com/ > which already contains the refcount field in stack_record. > (and maybe help with the review of that series as well? Hopefully it can get > to mm/unstable and -next towards 6.8 soon :) Yes, please; I just mailed a v4 that is based on v6.7-rc2: https://lore.kernel.org/linux-mm/cover.1700502145.git.andreyknvl@google.com/T/#t You should also be able to use the new stack_depot_save_flags(STACK_DEPOT_FLAG_GET)/stack_depot_put API to keep only the relevant stack traces. Thank you!
Changes v5 -> v6: - Rebase on top of v6.7-rc1 - Move stack_record struct to the header - Addressed feedback from Vlastimil (some code tweaks and changelogs suggestions) Changes v4 -> v5: - Addressed feedback from Alexander Potapenko Changes v3 -> v4: - Rebase (long time has passed) - Use boolean instead of enum for action by Alexander Potapenko - (I left some feedback untouched because it's been long and would like to discuss it here now instead of re-vamping and old thread) Changes v2 -> v3: - Replace interface in favor of seq operations (suggested by Vlastimil) - Use debugfs interface to store/read valued (suggested by Ammar) Hi, page_owner is a great debug functionality tool that lets us know about all pages that have been allocated/freed and their stacktrace. This comes very handy when one has to debug memory leaks, since with some scripting we can see outstanding allocations, which might end up pointing to a leak. In my experience, that is one of the most useful cases, but it can get really tedious to screen through all pages and try to reconstruct the stack <-> allocated/freed relationship. There is a lot of noise to cancel off. This patchset aims to ease that by adding a new functionality into page_owner. What this does is to create a new read-only file "page_owner_stacks", which prints out only the stacktraces followed by their outstanding number of allocations (being that the times the stacktrace has allocated but not freed yet). This lets us have a clear overview of stacks <-> allocated/freed relationship without the need to fiddle with pages and trying to match free stacktraces with allocated stacktraces. This is achieved by adding a new refcount_t field in the stack_record struct, incrementing that refcount_t everytime the same stacktrace allocates, and decrementing it when it frees a page. Details can be seen in the respective patches. We also create another file called "page_owner_threshold", which let us specify a threshold, so when reading from "page_owner_stacks", we will only see those stacktraces which counting goes beyond the threshold we specified. A PoC can be found below: # cat /sys/kernel/debug/page_owner_threshold 0 # cat /sys/kernel/debug/page_owner_stacks > stacks_full.txt # head -32 stacks_full.txt prep_new_page+0x10d/0x180 get_page_from_freelist+0x1bd6/0x1e10 __alloc_pages+0x194/0x360 alloc_page_interleave+0x13/0x90 new_slab+0x31d/0x530 ___slab_alloc+0x5d7/0x720 __slab_alloc.isra.85+0x4a/0x90 kmem_cache_alloc+0x455/0x4a0 acpi_ps_alloc_op+0x57/0x8f acpi_ps_create_scope_op+0x12/0x23 acpi_ps_execute_method+0x102/0x2c1 acpi_ns_evaluate+0x343/0x4da acpi_evaluate_object+0x1cb/0x392 acpi_run_osc+0x135/0x260 acpi_init+0x165/0x4ed do_one_initcall+0x3e/0x200 stack count: 2 free_pcp_prepare+0x287/0x5c0 free_unref_page+0x1c/0xd0 __mmdrop+0x50/0x160 finish_task_switch+0x249/0x2b0 __schedule+0x2c3/0x960 schedule+0x44/0xb0 futex_wait_queue+0x70/0xd0 futex_wait+0x160/0x250 do_futex+0x11c/0x1b0 __x64_sys_futex+0x5e/0x1d0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd stack count: 1 # echo 10000 > /sys/kernel/debug/page_owner_threshold # cat /sys/kernel/debug/page_owner_stacks > stacks_10000.txt # cat stacks_10000.txt prep_new_page+0x10d/0x180 get_page_from_freelist+0x1bd6/0x1e10 __alloc_pages+0x194/0x360 folio_alloc+0x17/0x40 page_cache_ra_unbounded+0x96/0x170 filemap_get_pages+0x23d/0x5e0 filemap_read+0xbf/0x3a0 __kernel_read+0x136/0x2f0 kernel_read_file+0x197/0x2d0 kernel_read_file_from_fd+0x54/0x90 __do_sys_finit_module+0x89/0x120 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd stack count: 36195 prep_new_page+0x10d/0x180 get_page_from_freelist+0x1bd6/0x1e10 __alloc_pages+0x194/0x360 folio_alloc+0x17/0x40 page_cache_ra_unbounded+0x96/0x170 filemap_get_pages+0x23d/0x5e0 filemap_read+0xbf/0x3a0 new_sync_read+0x106/0x180 vfs_read+0x16f/0x190 ksys_read+0xa5/0xe0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd stack count: 44484 prep_new_page+0x10d/0x180 get_page_from_freelist+0x1bd6/0x1e10 __alloc_pages+0x194/0x360 folio_alloc+0x17/0x40 page_cache_ra_unbounded+0x96/0x170 filemap_get_pages+0xdd/0x5e0 filemap_read+0xbf/0x3a0 new_sync_read+0x106/0x180 vfs_read+0x16f/0x190 ksys_read+0xa5/0xe0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd stack count: 17874 Oscar Salvador (4): lib/stackdepot: Add a refcount field in stack_record lib/stackdepot: Move stack_record struct definition into the header mm,page_owner: Add page_owner_stacks file to print out only stacks and their counter mm,page_owner: Filter out stacks by a threshold counter include/linux/stackdepot.h | 38 ++++++++++++ lib/stackdepot.c | 114 ++++++++++++++++++++++-------------- mm/page_owner.c | 115 +++++++++++++++++++++++++++++++++++++ 3 files changed, 224 insertions(+), 43 deletions(-)