From: Oliver Glitta <glittao@xxxxxxxxx> Subject: mm/slub: use stackdepot to save stack trace in objects Many stack traces are similar so there are many similar arrays. Stackdepot saves each unique stack only once. Replace field addrs in struct track with depot_stack_handle_t handle. Use stackdepot to save stack trace. The benefits are smaller memory overhead and possibility to aggregate per-cache statistics in the future using the stackdepot handle instead of matching stacks manually. [rdunlap@xxxxxxxxxxxxx: rename save_stack_trace()] Link: https://lkml.kernel.org/r/20210513051920.29320-1-rdunlap@xxxxxxxxxxxxx [vbabka@xxxxxxx: fix lockdep splat] Link: https://lkml.kernel.org/r/20210516195150.26740-1-vbabka@suse.czLink: https://lkml.kernel.org/r/20210414163434.4376-1-glittao@xxxxxxxxx Signed-off-by: Oliver Glitta <glittao@xxxxxxxxx> Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- init/Kconfig | 1 mm/slub.c | 79 ++++++++++++++++++++++++++++++------------------- 2 files changed, 50 insertions(+), 30 deletions(-) --- a/init/Kconfig~mm-slub-use-stackdepot-to-save-stack-trace-in-objects +++ a/init/Kconfig @@ -1847,6 +1847,7 @@ config SLUB_DEBUG default y bool "Enable SLUB debugging support" if EXPERT depends on SLUB && SYSFS + select STACKDEPOT if STACKTRACE_SUPPORT help SLUB has extensive debug support features. Disabling these can result in significant savings in code size. This also disables --- a/mm/slub.c~mm-slub-use-stackdepot-to-save-stack-trace-in-objects +++ a/mm/slub.c @@ -26,6 +26,7 @@ #include <linux/cpuset.h> #include <linux/mempolicy.h> #include <linux/ctype.h> +#include <linux/stackdepot.h> #include <linux/debugobjects.h> #include <linux/kallsyms.h> #include <linux/kfence.h> @@ -220,8 +221,8 @@ static inline bool kmem_cache_has_cpu_pa #define TRACK_ADDRS_COUNT 16 struct track { unsigned long addr; /* Called from address */ -#ifdef CONFIG_STACKTRACE - unsigned long addrs[TRACK_ADDRS_COUNT]; /* Called from address */ +#ifdef CONFIG_STACKDEPOT + depot_stack_handle_t handle; #endif int cpu; /* Was running on cpu */ int pid; /* Pid context */ @@ -625,22 +626,27 @@ static struct track *get_track(struct km return kasan_reset_tag(p + alloc); } +#ifdef CONFIG_STACKDEPOT +static depot_stack_handle_t save_stack_depot_trace(gfp_t flags) +{ + unsigned long entries[TRACK_ADDRS_COUNT]; + depot_stack_handle_t handle; + unsigned int nr_entries; + + nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 4); + handle = stack_depot_save(entries, nr_entries, flags); + return handle; +} +#endif + static void set_track(struct kmem_cache *s, void *object, enum track_item alloc, unsigned long addr) { struct track *p = get_track(s, object, alloc); if (addr) { -#ifdef CONFIG_STACKTRACE - unsigned int nr_entries; - - metadata_access_enable(); - nr_entries = stack_trace_save(kasan_reset_tag(p->addrs), - TRACK_ADDRS_COUNT, 3); - metadata_access_disable(); - - if (nr_entries < TRACK_ADDRS_COUNT) - p->addrs[nr_entries] = 0; +#ifdef CONFIG_STACKDEPOT + p->handle = save_stack_depot_trace(GFP_NOWAIT); #endif p->addr = addr; p->cpu = smp_processor_id(); @@ -667,14 +673,19 @@ static void print_track(const char *s, s pr_err("%s in %pS age=%lu cpu=%u pid=%d\n", s, (void *)t->addr, pr_time - t->when, t->cpu, t->pid); -#ifdef CONFIG_STACKTRACE +#ifdef CONFIG_STACKDEPOT { - int i; - for (i = 0; i < TRACK_ADDRS_COUNT; i++) - if (t->addrs[i]) - pr_err("\t%pS\n", (void *)t->addrs[i]); - else - break; + depot_stack_handle_t handle; + unsigned long *entries; + unsigned int nr_entries; + + handle = READ_ONCE(t->handle); + if (!handle) { + pr_err("object allocation/free stack trace missing\n"); + } else { + nr_entries = stack_depot_fetch(handle, &entries); + stack_trace_print(entries, nr_entries, 0); + } } #endif } @@ -4048,18 +4059,26 @@ void kmem_obj_info(struct kmem_obj_info objp = fixup_red_left(s, objp); trackp = get_track(s, objp, TRACK_ALLOC); kpp->kp_ret = (void *)trackp->addr; -#ifdef CONFIG_STACKTRACE - for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) { - kpp->kp_stack[i] = (void *)trackp->addrs[i]; - if (!kpp->kp_stack[i]) - break; - } +#ifdef CONFIG_STACKDEPOT + { + depot_stack_handle_t handle; + unsigned long *entries; + unsigned int nr_entries; - trackp = get_track(s, objp, TRACK_FREE); - for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) { - kpp->kp_free_stack[i] = (void *)trackp->addrs[i]; - if (!kpp->kp_free_stack[i]) - break; + handle = READ_ONCE(trackp->handle); + if (handle) { + nr_entries = stack_depot_fetch(handle, &entries); + for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++) + kpp->kp_stack[i] = (void *)entries[i]; + } + + trackp = get_track(s, objp, TRACK_FREE); + handle = READ_ONCE(trackp->handle); + if (handle) { + nr_entries = stack_depot_fetch(handle, &entries); + for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++) + kpp->kp_free_stack[i] = (void *)entries[i]; + } } #endif #endif _
