From: Suren Baghdasaryan Date: Mon, 15 Sep 2025 23:02:24 +0000 (-0700) Subject: alloc_tag: mark inaccurate allocation counters in /proc/allocinfo output X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b9e2f58ffb84afcbba7e66f96ca14f98e0e88f26;p=thirdparty%2Fkernel%2Fstable.git alloc_tag: mark inaccurate allocation counters in /proc/allocinfo output While rare, memory allocation profiling can contain inaccurate counters if slab object extension vector allocation fails. That allocation might succeed later but prior to that, slab allocations that would have used that object extension vector will not be accounted for. To indicate incorrect counters, "accurate:no" marker is appended to the call site line in the /proc/allocinfo output. Bump up /proc/allocinfo version to reflect the change in the file format and update documentation. Example output with invalid counters: allocinfo - version: 2.0 0 0 arch/x86/kernel/kdebugfs.c:105 func:create_setup_data_nodes 0 0 arch/x86/kernel/alternative.c:2090 func:alternatives_smp_module_add 0 0 arch/x86/kernel/alternative.c:127 func:__its_alloc accurate:no 0 0 arch/x86/kernel/fpu/regset.c:160 func:xstateregs_set 0 0 arch/x86/kernel/fpu/xstate.c:1590 func:fpstate_realloc 0 0 arch/x86/kernel/cpu/aperfmperf.c:379 func:arch_enable_hybrid_capacity_scale 0 0 arch/x86/kernel/cpu/amd_cache_disable.c:258 func:init_amd_l3_attrs 49152 48 arch/x86/kernel/cpu/mce/core.c:2709 func:mce_device_create accurate:no 32768 1 arch/x86/kernel/cpu/mce/genpool.c:132 func:mce_gen_pool_create 0 0 arch/x86/kernel/cpu/mce/amd.c:1341 func:mce_threshold_create_device [surenb@google.com: document new "accurate:no" marker] Fixes: 39d117e04d15 ("alloc_tag: mark inaccurate allocation counters in /proc/allocinfo output") [akpm@linux-foundation.org: simplification per Usama, reflow text] [akpm@linux-foundation.org: add newline to prevent docs warning, per Randy] Link: https://lkml.kernel.org/r/20250915230224.4115531-1-surenb@google.com Signed-off-by: Suren Baghdasaryan Suggested-by: Johannes Weiner Acked-by: Shakeel Butt Acked-by: Usama Arif Acked-by: Johannes Weiner Cc: David Rientjes Cc: David Wang <00107082@163.com> Cc: Kent Overstreet Cc: Pasha Tatashin Cc: Roman Gushchin Cc: Sourav Panda Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 915a3e44bc120..6ffd04c736db6 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -1009,6 +1009,19 @@ number, module (if originates from a loadable module) and the function calling the allocation. The number of bytes allocated and number of calls at each location are reported. The first line indicates the version of the file, the second line is the header listing fields in the file. +If file version is 2.0 or higher then each line may contain additional +: pairs representing extra information about the call site. +For example if the counters are not accurate, the line will be appended with +"accurate:no" pair. + +Supported markers in v2: +accurate:no + + Absolute values of the counters in this line are not accurate + because of the failure to allocate memory to track some of the + allocations made at this location. Deltas in these counters are + accurate, therefore counters can be used to track allocation size + and count changes. Example output. diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h index 9ef2633e2c08c..d40ac39bfbe8d 100644 --- a/include/linux/alloc_tag.h +++ b/include/linux/alloc_tag.h @@ -221,6 +221,16 @@ static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) ref->ct = NULL; } +static inline void alloc_tag_set_inaccurate(struct alloc_tag *tag) +{ + tag->ct.flags |= CODETAG_FLAG_INACCURATE; +} + +static inline bool alloc_tag_is_inaccurate(struct alloc_tag *tag) +{ + return !!(tag->ct.flags & CODETAG_FLAG_INACCURATE); +} + #define alloc_tag_record(p) ((p) = current->alloc_tag) #else /* CONFIG_MEM_ALLOC_PROFILING */ @@ -230,6 +240,8 @@ static inline bool mem_alloc_profiling_enabled(void) { return false; } static inline void alloc_tag_add(union codetag_ref *ref, struct alloc_tag *tag, size_t bytes) {} static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) {} +static inline void alloc_tag_set_inaccurate(struct alloc_tag *tag) {} +static inline bool alloc_tag_is_inaccurate(struct alloc_tag *tag) { return false; } #define alloc_tag_record(p) do {} while (0) #endif /* CONFIG_MEM_ALLOC_PROFILING */ diff --git a/include/linux/codetag.h b/include/linux/codetag.h index 457ed8fd32144..8ea2a5f7c98a5 100644 --- a/include/linux/codetag.h +++ b/include/linux/codetag.h @@ -16,13 +16,16 @@ struct module; #define CODETAG_SECTION_START_PREFIX "__start_" #define CODETAG_SECTION_STOP_PREFIX "__stop_" +/* codetag flags */ +#define CODETAG_FLAG_INACCURATE (1 << 0) + /* * An instance of this structure is created in a special ELF section at every * code location being tagged. At runtime, the special section is treated as * an array of these. */ struct codetag { - unsigned int flags; /* used in later patches */ + unsigned int flags; unsigned int lineno; const char *modname; const char *function; diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c index f79217427d812..3ef702e6b69a8 100644 --- a/lib/alloc_tag.c +++ b/lib/alloc_tag.c @@ -80,7 +80,7 @@ static void allocinfo_stop(struct seq_file *m, void *arg) static void print_allocinfo_header(struct seq_buf *buf) { /* Output format version, so we can change it. */ - seq_buf_printf(buf, "allocinfo - version: 1.0\n"); + seq_buf_printf(buf, "allocinfo - version: 2.0\n"); seq_buf_printf(buf, "# \n"); } @@ -92,6 +92,8 @@ static void alloc_tag_to_text(struct seq_buf *out, struct codetag *ct) seq_buf_printf(out, "%12lli %8llu ", bytes, counter.calls); codetag_to_text(out, ct); + if (unlikely(alloc_tag_is_inaccurate(tag))) + seq_buf_printf(out, " accurate:no"); seq_buf_putc(out, ' '); seq_buf_putc(out, '\n'); } diff --git a/mm/slub.c b/mm/slub.c index af343ca570b57..9c04f29ee8dee 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2143,6 +2143,8 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags) */ if (likely(obj_exts)) alloc_tag_add(&obj_exts->ref, current->alloc_tag, s->size); + else + alloc_tag_set_inaccurate(current->alloc_tag); } static inline void