On Wed, Mar 02, 2022 at 06:31:19PM +0100, Vlastimil Babka wrote:
> From: Oliver Glitta <glittao@xxxxxxxxx>
>
> 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 following patch using the stackdepot handle
> instead of matching stacks manually.
>
> [ vbabka@xxxxxxx: rebase to 5.17-rc1 and adjust accordingly ]
>
> This was initially merged as commit 788691464c29 and reverted by commit
> ae14c63a9f20 due to several issues, that should now be fixed.
> The problem of unconditional memory overhead by stackdepot has been
> addressed by commit 2dba5eb1c73b ("lib/stackdepot: allow optional init
> and stack_table allocation by kvmalloc()"), so the dependency on
> stackdepot will result in extra memory usage only when a slab cache
> tracking is actually enabled, and not for all CONFIG_SLUB_DEBUG builds.
> The build failures on some architectures were also addressed, and the
> reported issue with xfs/433 test did not reproduce on 5.17-rc1 with this
> patch.
>
> Signed-off-by: Oliver Glitta <glittao@xxxxxxxxx>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Pekka Enberg <penberg@xxxxxxxxxx>
> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> ---
> init/Kconfig | 1 +
> mm/slab_common.c | 5 ++++
> mm/slub.c | 71 +++++++++++++++++++++++++++---------------------
> 3 files changed, 46 insertions(+), 31 deletions(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index e9119bf54b1f..b21dd3a4a106 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1871,6 +1871,7 @@ 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
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 23f2ab0713b7..e51d50d03000 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -24,6 +24,7 @@
> #include <asm/tlbflush.h>
> #include <asm/page.h>
> #include <linux/memcontrol.h>
> +#include <linux/stackdepot.h>
>
> #define CREATE_TRACE_POINTS
> #include <trace/events/kmem.h>
> @@ -314,9 +315,13 @@ kmem_cache_create_usercopy(const char *name,
> * If no slub_debug was enabled globally, the static key is not yet
> * enabled by setup_slub_debug(). Enable it if the cache is being
> * created with any of the debugging flags passed explicitly.
> + * It's also possible that this is the first cache created with
> + * SLAB_STORE_USER and we should init stack_depot for it.
> */
> if (flags & SLAB_DEBUG_FLAGS)
> static_branch_enable(&slub_debug_enabled);
> + if (flags & SLAB_STORE_USER && IS_ENABLED(CONFIG_STACKDEPOT))
> + stack_depot_init();
> #endif
Is this comment and code still valid in v3?
> mutex_lock(&slab_mutex);
> diff --git a/mm/slub.c b/mm/slub.c
> index 1fc451f4fe62..42cb79af70a0 100644
> --- a/mm/slub.c
> +++ b/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>
> @@ -264,8 +265,8 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
> #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 */
> @@ -724,22 +725,19 @@ static struct track *get_track(struct kmem_cache *s, void *object,
> return kasan_reset_tag(p + alloc);
> }
>
> -static void set_track(struct kmem_cache *s, void *object,
> +static void noinline set_track(struct kmem_cache *s, void *object,
> enum track_item alloc, unsigned long addr)
> {
noinline for debugging purpose?
I think it's okay. just a question.
> struct track *p = get_track(s, object, alloc);
>
> -#ifdef CONFIG_STACKTRACE
> +#ifdef CONFIG_STACKDEPOT
> + unsigned long entries[TRACK_ADDRS_COUNT];
> 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;
> + nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
> + p->handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
> #endif
> +
> p->addr = addr;
> p->cpu = smp_processor_id();
> p->pid = current->pid;
> @@ -759,20 +757,19 @@ static void init_tracking(struct kmem_cache *s, void *object)
>
> static void print_track(const char *s, struct track *t, unsigned long pr_time)
> {
> + depot_stack_handle_t handle __maybe_unused;
> +
> if (!t->addr)
> return;
>
> 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
> - {
> - 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;
> - }
> +#ifdef CONFIG_STACKDEPOT
> + handle = READ_ONCE(t->handle);
> + if (handle)
> + stack_depot_print(handle);
> + else
> + pr_err("object allocation/free stack trace missing\n");
> #endif
> }
>
> @@ -1532,6 +1529,8 @@ static int __init setup_slub_debug(char *str)
> global_slub_debug_changed = true;
> } else {
> slab_list_specified = true;
> + if (flags & SLAB_STORE_USER)
> + stack_depot_want_early_init = true;
This is updated to stack_depot_want_early_init() in v3.
> }
> }
>
> @@ -1549,6 +1548,8 @@ static int __init setup_slub_debug(char *str)
> }
> out:
> slub_debug = global_flags;
> + if (slub_debug & SLAB_STORE_USER)
> + stack_depot_want_early_init = true;
This too.
> if (slub_debug != 0 || slub_debug_string)
> static_branch_enable(&slub_debug_enabled);
> else
> @@ -4352,18 +4353,26 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
> 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;
> +
> + 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);
> - 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;
> + 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
> --
> 2.35.1
Otherwise looks good.
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
kmem_dump_obj() and slab error report functionality works fine.
Tested-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
--
Thank you, You are awesome!
Hyeonggon :-)
