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SubjectRe: [PATCH] mm: memcontrol: use vmalloc fallback for large kmem memcg arrays
On Mon 18-09-17 14:49:19, Johannes Weiner wrote:
> For quick per-memcg indexing, slab caches and list_lru structures
> maintain linear arrays of descriptors. As the number of concurrent
> memory cgroups in the system goes up, this requires large contiguous
> allocations (8k cgroups = order-5, 16k cgroups = order-6 etc.) for
> every existing slab cache and list_lru, which can easily fail on
> loaded systems. E.g.:
>
> mkdir: page allocation failure: order:5, mode:0x14040c0(GFP_KERNEL|__GFP_COMP), nodemask=(null)
> CPU: 1 PID: 6399 Comm: mkdir Not tainted 4.13.0-mm1-00065-g720bbe532b7c-dirty #481
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-20170228_101828-anatol 04/01/2014
> Call Trace:
> dump_stack+0x70/0x9d
> warn_alloc+0xd6/0x170
> ? __alloc_pages_direct_compact+0x4c/0x110
> __alloc_pages_nodemask+0xf50/0x1430
> ? __lock_acquire+0xd19/0x1360
> ? memcg_update_all_list_lrus+0x2e/0x2e0
> ? __mutex_lock+0x7c/0x950
> ? memcg_update_all_list_lrus+0x2e/0x2e0
> alloc_pages_current+0x60/0xc0
> kmalloc_order_trace+0x29/0x1b0
> __kmalloc+0x1f4/0x320
> memcg_update_all_list_lrus+0xca/0x2e0
> mem_cgroup_css_alloc+0x612/0x670
> cgroup_apply_control_enable+0x19e/0x360
> cgroup_mkdir+0x322/0x490
> kernfs_iop_mkdir+0x55/0x80
> vfs_mkdir+0xd0/0x120
> SyS_mkdirat+0x6c/0xe0
> SyS_mkdir+0x14/0x20
> entry_SYSCALL_64_fastpath+0x18/0xad
> RIP: 0033:0x7f9ff36cee87
> RSP: 002b:00007ffc7612d758 EFLAGS: 00000202 ORIG_RAX: 0000000000000053
> RAX: ffffffffffffffda RBX: 00007ffc7612da48 RCX: 00007f9ff36cee87
> RDX: 00000000000001ff RSI: 00000000000001ff RDI: 00007ffc7612de86
> RBP: 0000000000000002 R08: 00000000000001ff R09: 0000000000401db0
> R10: 00000000000001e2 R11: 0000000000000202 R12: 0000000000000000
> R13: 00007ffc7612da40 R14: 0000000000000000 R15: 0000000000000000
> Mem-Info:
> active_anon:2965 inactive_anon:19 isolated_anon:0
> active_file:100270 inactive_file:98846 isolated_file:0
> unevictable:0 dirty:0 writeback:0 unstable:0
> slab_reclaimable:7328 slab_unreclaimable:16402
> mapped:771 shmem:52 pagetables:278 bounce:0
> free:13718 free_pcp:0 free_cma:0
>
> This output is from an artificial reproducer, but we have repeatedly
> observed order-7 failures in production in the Facebook fleet. These
> systems become useless as they cannot run more jobs, even though there
> is plenty of memory to allocate 128 individual pages.
>
> Use kvmalloc and kvzalloc to fall back to vmalloc space if these
> arrays prove too large for allocating them physically contiguous.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/list_lru.c | 12 ++++++------
> mm/slab_common.c | 22 +++++++++++++++-------
> 2 files changed, 21 insertions(+), 13 deletions(-)
>
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index 7a40fa2be858..f141f0c80ff3 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -325,12 +325,12 @@ static int memcg_init_list_lru_node(struct list_lru_node *nlru)
> {
> int size = memcg_nr_cache_ids;
>
> - nlru->memcg_lrus = kmalloc(size * sizeof(void *), GFP_KERNEL);
> + nlru->memcg_lrus = kvmalloc(size * sizeof(void *), GFP_KERNEL);
> if (!nlru->memcg_lrus)
> return -ENOMEM;
>
> if (__memcg_init_list_lru_node(nlru->memcg_lrus, 0, size)) {
> - kfree(nlru->memcg_lrus);
> + kvfree(nlru->memcg_lrus);
> return -ENOMEM;
> }
>
> @@ -340,7 +340,7 @@ static int memcg_init_list_lru_node(struct list_lru_node *nlru)
> static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
> {
> __memcg_destroy_list_lru_node(nlru->memcg_lrus, 0, memcg_nr_cache_ids);
> - kfree(nlru->memcg_lrus);
> + kvfree(nlru->memcg_lrus);
> }
>
> static int memcg_update_list_lru_node(struct list_lru_node *nlru,
> @@ -351,12 +351,12 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
> BUG_ON(old_size > new_size);
>
> old = nlru->memcg_lrus;
> - new = kmalloc(new_size * sizeof(void *), GFP_KERNEL);
> + new = kvmalloc(new_size * sizeof(void *), GFP_KERNEL);
> if (!new)
> return -ENOMEM;
>
> if (__memcg_init_list_lru_node(new, old_size, new_size)) {
> - kfree(new);
> + kvfree(new);
> return -ENOMEM;
> }
>
> @@ -373,7 +373,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
> nlru->memcg_lrus = new;
> spin_unlock_irq(&nlru->lock);
>
> - kfree(old);
> + kvfree(old);
> return 0;
> }
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 904a83be82de..80164599ca5d 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -165,9 +165,9 @@ static int init_memcg_params(struct kmem_cache *s,
> if (!memcg_nr_cache_ids)
> return 0;
>
> - arr = kzalloc(sizeof(struct memcg_cache_array) +
> - memcg_nr_cache_ids * sizeof(void *),
> - GFP_KERNEL);
> + arr = kvzalloc(sizeof(struct memcg_cache_array) +
> + memcg_nr_cache_ids * sizeof(void *),
> + GFP_KERNEL);
> if (!arr)
> return -ENOMEM;
>
> @@ -178,15 +178,23 @@ static int init_memcg_params(struct kmem_cache *s,
> static void destroy_memcg_params(struct kmem_cache *s)
> {
> if (is_root_cache(s))
> - kfree(rcu_access_pointer(s->memcg_params.memcg_caches));
> + kvfree(rcu_access_pointer(s->memcg_params.memcg_caches));
> +}
> +
> +static void free_memcg_params(struct rcu_head *rcu)
> +{
> + struct memcg_cache_array *old;
> +
> + old = container_of(rcu, struct memcg_cache_array, rcu);
> + kvfree(old);
> }
>
> static int update_memcg_params(struct kmem_cache *s, int new_array_size)
> {
> struct memcg_cache_array *old, *new;
>
> - new = kzalloc(sizeof(struct memcg_cache_array) +
> - new_array_size * sizeof(void *), GFP_KERNEL);
> + new = kvzalloc(sizeof(struct memcg_cache_array) +
> + new_array_size * sizeof(void *), GFP_KERNEL);
> if (!new)
> return -ENOMEM;
>
> @@ -198,7 +206,7 @@ static int update_memcg_params(struct kmem_cache *s, int new_array_size)
>
> rcu_assign_pointer(s->memcg_params.memcg_caches, new);
> if (old)
> - kfree_rcu(old, rcu);
> + call_rcu(&old->rcu, free_memcg_params);
> return 0;
> }
>
> --
> 2.14.1
>

--
Michal Hocko
SUSE Labs

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