From: "Yang Shi" <yang.s@xxxxxxxxxxxxxxx> Subject: mm: oom: show unreclaimable slab info when unreclaimable slabs > user memory Kernel may panic when oom happens without killable process sometimes it is caused by huge unreclaimable slabs used by kernel. Although kdump could help debug such problem, however, kdump is not available on all architectures and it might be malfunction sometime. And, since kernel already panic it is worthy capturing such information in dmesg to aid touble shooting. Print out unreclaimable slab info (used size and total size) which actual memory usage is not zero (num_objs * size != 0) when unreclaimable slabs amount is greater than total user memory (LRU pages). The output looks like: Unreclaimable slab info: Name Used Total rpc_buffers 31KB 31KB rpc_tasks 7KB 7KB ebitmap_node 1964KB 1964KB avtab_node 5024KB 5024KB xfs_buf 1402KB 1402KB xfs_ili 134KB 134KB xfs_efi_item 115KB 115KB xfs_efd_item 115KB 115KB xfs_buf_item 134KB 134KB xfs_log_item_desc 342KB 342KB xfs_trans 1412KB 1412KB xfs_ifork 212KB 212KB [yang.s@xxxxxxxxxxxxxxx: v11] Link: http://lkml.kernel.org/r/1507656303-103845-4-git-send-email-yang.s@xxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/1507152550-46205-4-git-send-email-yang.s@xxxxxxxxxxxxxxx Signed-off-by: Yang Shi <yang.s@xxxxxxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/oom_kill.c | 27 +++++++++++++++++++++++++-- mm/slab.h | 8 ++++++++ mm/slab_common.c | 34 ++++++++++++++++++++++++++++++++++ 3 files changed, 67 insertions(+), 2 deletions(-) diff -puN mm/oom_kill.c~mm-oom-show-unreclaimable-slab-info-when-unreclaimable-slabs-user-memory mm/oom_kill.c --- a/mm/oom_kill.c~mm-oom-show-unreclaimable-slab-info-when-unreclaimable-slabs-user-memory +++ a/mm/oom_kill.c @@ -44,6 +44,7 @@ #include <asm/tlb.h> #include "internal.h" +#include "slab.h" #define CREATE_TRACE_POINTS #include <trace/events/oom.h> @@ -161,6 +162,25 @@ static bool oom_unkillable_task(struct t return false; } +/* + * Print out unreclaimble slabs info when unreclaimable slabs amount is greater + * than all user memory (LRU pages) + */ +static bool is_dump_unreclaim_slabs(void) +{ + unsigned long nr_lru; + + nr_lru = global_node_page_state(NR_ACTIVE_ANON) + + global_node_page_state(NR_INACTIVE_ANON) + + global_node_page_state(NR_ACTIVE_FILE) + + global_node_page_state(NR_INACTIVE_FILE) + + global_node_page_state(NR_ISOLATED_ANON) + + global_node_page_state(NR_ISOLATED_FILE) + + global_node_page_state(NR_UNEVICTABLE); + + return (global_node_page_state(NR_SLAB_UNRECLAIMABLE) > nr_lru); +} + /** * oom_badness - heuristic function to determine which candidate task to kill * @p: task struct of which task we should calculate @@ -420,10 +440,13 @@ static void dump_header(struct oom_contr cpuset_print_current_mems_allowed(); dump_stack(); - if (oc->memcg) + if (is_memcg_oom(oc)) mem_cgroup_print_oom_info(oc->memcg, p); - else + else { show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask); + if (is_dump_unreclaim_slabs()) + dump_unreclaimable_slab(); + } if (sysctl_oom_dump_tasks) dump_tasks(oc->memcg, oc->nodemask); } diff -puN mm/slab_common.c~mm-oom-show-unreclaimable-slab-info-when-unreclaimable-slabs-user-memory mm/slab_common.c --- a/mm/slab_common.c~mm-oom-show-unreclaimable-slab-info-when-unreclaimable-slabs-user-memory +++ a/mm/slab_common.c @@ -1280,6 +1280,40 @@ static int slab_show(struct seq_file *m, return 0; } +void dump_unreclaimable_slab(void) +{ + struct kmem_cache *s, *s2; + struct slabinfo sinfo; + + /* + * Here acquiring slab_mutex is risky since we don't prefer to get + * sleep in oom path. But, without mutex hold, it may introduce a + * risk of crash. + * Use mutex_trylock to protect the list traverse, dump nothing + * without acquiring the mutex. + */ + if (!mutex_trylock(&slab_mutex)) { + pr_warn("excessive unreclaimable slab but cannot dump stats\n"); + return; + } + + pr_info("Unreclaimable slab info:\n"); + pr_info("Name Used Total\n"); + + list_for_each_entry_safe(s, s2, &slab_caches, list) { + if (!is_root_cache(s) || (s->flags & SLAB_RECLAIM_ACCOUNT)) + continue; + + get_slabinfo(s, &sinfo); + + if (sinfo.num_objs > 0) + pr_info("%-17s %10luKB %10luKB\n", cache_name(s), + (sinfo.active_objs * s->size) / 1024, + (sinfo.num_objs * s->size) / 1024); + } + mutex_unlock(&slab_mutex); +} + #if defined(CONFIG_MEMCG) void *memcg_slab_start(struct seq_file *m, loff_t *pos) { diff -puN mm/slab.h~mm-oom-show-unreclaimable-slab-info-when-unreclaimable-slabs-user-memory mm/slab.h --- a/mm/slab.h~mm-oom-show-unreclaimable-slab-info-when-unreclaimable-slabs-user-memory +++ a/mm/slab.h @@ -506,6 +506,14 @@ void *memcg_slab_next(struct seq_file *m void memcg_slab_stop(struct seq_file *m, void *p); int memcg_slab_show(struct seq_file *m, void *p); +#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG) +void dump_unreclaimable_slab(void); +#else +static inline void dump_unreclaimable_slab(void) +{ +} +#endif + void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr); #ifdef CONFIG_SLAB_FREELIST_RANDOM _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
