On Mon 13-09-21 15:38:29, Feng Tang wrote:
> There was report that starting an Ubuntu in docker while using cpuset
> to bind it to movable nodes (a node only has movable zone, like a node
> for hotplug or a Persistent Memory node in normal usage) will fail
> due to memory allocation failure, and then OOM is involved and many
> other innocent processes got killed. It can be reproduced with command:
> $docker run -it --rm --cpuset-mems 4 ubuntu:latest bash -c
> "grep Mems_allowed /proc/self/status" (node 4 is a movable node)
>
>
> runc:[2:INIT] invoked oom-killer: gfp_mask=0x500cc2(GFP_HIGHUSER|__GFP_ACCOUNT), order=0, oom_score_adj=0
> CPU: 8 PID: 8291 Comm: runc:[2:INIT] Tainted: G W I E 5.8.2-0.g71b519a-default #1 openSUSE Tumbleweed (unreleased)
> Hardware name: Dell Inc. PowerEdge R640/0PHYDR, BIOS 2.6.4 04/09/2020
> Call Trace:
> dump_stack+0x6b/0x88
> dump_header+0x4a/0x1e2
> oom_kill_process.cold+0xb/0x10
> out_of_memory.part.0+0xaf/0x230
> out_of_memory+0x3d/0x80
> __alloc_pages_slowpath.constprop.0+0x954/0xa20
> __alloc_pages_nodemask+0x2d3/0x300
> pipe_write+0x322/0x590
> new_sync_write+0x196/0x1b0
> vfs_write+0x1c3/0x1f0
> ksys_write+0xa7/0xe0
> do_syscall_64+0x52/0xd0
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Mem-Info:
> active_anon:392832 inactive_anon:182 isolated_anon:0
> active_file:68130 inactive_file:151527 isolated_file:0
> unevictable:2701 dirty:0 writeback:7
> slab_reclaimable:51418 slab_unreclaimable:116300
> mapped:45825 shmem:735 pagetables:2540 bounce:0
> free:159849484 free_pcp:73 free_cma:0
> Node 4 active_anon:1448kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB shmem:0kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB all_unreclaimable? no
> Node 4 Movable free:130021408kB min:9140kB low:139160kB high:269180kB reserved_highatomic:0KB active_anon:1448kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:130023424kB managed:130023424kB mlocked:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:292kB local_pcp:84kB free_cma:0kB
> lowmem_reserve[]: 0 0 0 0 0
> Node 4 Movable: 1*4kB (M) 0*8kB 0*16kB 1*32kB (M) 0*64kB 0*128kB 1*256kB (M) 1*512kB (M) 1*1024kB (M) 0*2048kB 31743*4096kB (M) = 130021156kB
>
> oom-kill:constraint=CONSTRAINT_CPUSET,nodemask=(null),cpuset=docker-9976a269caec812c134fa317f27487ee36e1129beba7278a463dd53e5fb9997b.scope,mems_allowed=4,global_oom,task_memcg=/system.slice/containerd.service,task=containerd,pid=4100,uid=0
> Out of memory: Killed process 4100 (containerd) total-vm:4077036kB, anon-rss:51184kB, file-rss:26016kB, shmem-rss:0kB, UID:0 pgtables:676kB oom_score_adj:0
> oom_reaper: reaped process 8248 (docker), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
> oom_reaper: reaped process 2054 (node_exporter), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
> oom_reaper: reaped process 1452 (systemd-journal), now anon-rss:0kB, file-rss:8564kB, shmem-rss:4kB
> oom_reaper: reaped process 2146 (munin-node), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
> oom_reaper: reaped process 8291 (runc:[2:INIT]), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
>
>
> The reason is, in the case, the target cpuset nodes only have movable
> zone, while the creation of an OS in docker sometimes needs to allocate
> memory in non-movable zones (dma/dma32/normal) like GFP_HIGHUSER, and
> the cpuset limit forbids the allocation, then out-of-memory killing is
> involved even when normal nodes and movable nodes both have many free
> memory.
>
> The OOM killer cannot help to resolve the situation as there is no
> usable memory for the request in the cpuset scope. The only reasonable
> measure to take is to fail the allocation right away and have the caller
> to deal with it.
>
> So add a check for cases like this in the slowpath of allocation, and
> bail out early returning NULL for the allocation.
>
> As page allocation is one of the hottest path in kernel, this check
> will hurt all users with sane cpuset configuration, add a static branch
> check and detect the abnormal config in cpuset memory binding setup so
> that the extra check in page allocation is not paid by everyone.
>
> [thanks to Micho Hocko and David Rientjes for suggesting not handle
> it inside OOM code, adding cpuset check, refining comments]
>
> Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
> Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
> ---
> Changelog:
>
> v2:
> * add a static branch detection in cpuset code to reduce
> the overhead in allocation hotpath (Michal Hocko)
>
> v1 (since RFC):
> * move the handling from oom code to page allocation
> path (Michal/David)
>
> include/linux/cpuset.h | 15 +++++++++++++++
> include/linux/mmzone.h | 12 ++++++++++++
> kernel/cgroup/cpuset.c | 14 ++++++++++++++
> mm/page_alloc.c | 13 +++++++++++++
> 4 files changed, 54 insertions(+)
>
> diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
> index d2b9c41..403ccf9 100644
> --- a/include/linux/cpuset.h
> +++ b/include/linux/cpuset.h
> @@ -34,6 +34,8 @@
> */
> extern struct static_key_false cpusets_pre_enable_key;
> extern struct static_key_false cpusets_enabled_key;
> +extern struct static_key_false cpusets_insane_config_key;
> +
> static inline bool cpusets_enabled(void)
> {
> return static_branch_unlikely(&cpusets_enabled_key);
> @@ -51,6 +53,19 @@ static inline void cpuset_dec(void)
> static_branch_dec_cpuslocked(&cpusets_pre_enable_key);
> }
>
> +/*
> + * This will get enabled whenever a cpuset configuration is considered
> + * unsupportable in general. E.g. movable only node which cannot satisfy
> + * any non movable allocations (see update_nodemask). Page allocator
> + * needs to make additional checks for those configurations and this
> + * check is meant to guard those checks without any overhead for sane
> + * configurations.
> + */
> +static inline bool cpusets_insane_config(void)
> +{
> + return static_branch_unlikely(&cpusets_insane_config_key);
> +}
> +
> extern int cpuset_init(void);
> extern void cpuset_init_smp(void);
> extern void cpuset_force_rebuild(void);
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 6a1d79d..b69b871 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1220,6 +1220,18 @@ static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
> #define for_each_zone_zonelist(zone, z, zlist, highidx) \
> for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, NULL)
>
> +/* Whether the 'nodes' are all movable nodes */
> +static inline bool movable_only_nodes(nodemask_t *nodes)
> +{
> + struct zonelist *zonelist;
> + struct zoneref *z;
> +
> + zonelist = &(first_online_pgdat())->node_zonelists[ZONELIST_FALLBACK];
This will work but it just begs a question why you haven't chosen a node
from the given nodemask. So I believe it would be easier to read if you
did
zonelist = NODE_DATA(first_node(nodes))->node_zonelists[ZONELIST_FALLBACK]
> + z = first_zones_zonelist(zonelist, ZONE_NORMAL, nodes);
> + return (!z->zone) ? true : false;
> +}
> +
> +
> #ifdef CONFIG_SPARSEMEM
> #include <asm/sparsemem.h>
> #endif
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index df1ccf4..03eb40c 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -69,6 +69,13 @@
> DEFINE_STATIC_KEY_FALSE(cpusets_pre_enable_key);
> DEFINE_STATIC_KEY_FALSE(cpusets_enabled_key);
>
> +/*
> + * There could be abnormal cpuset configurations for cpu or memory
> + * node binding, add this key to provide a quick low-cost judgement
> + * of the situation.
> + */
> +DEFINE_STATIC_KEY_FALSE(cpusets_insane_config_key);
> +
> /* See "Frequency meter" comments, below. */
>
> struct fmeter {
> @@ -1868,6 +1875,13 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
> if (retval < 0)
> goto done;
>
> + if (movable_only_nodes(&trialcs->mems_allowed)) {
You can skip the check if cpusets_insane_config(). The question is
whether you want to report all potential users or only the first one.
> + static_branch_enable(&cpusets_insane_config_key);
> + pr_info("Unsupported (movable nodes only) cpuset configuration detected (nmask=%*pbl)! "
> + "Cpuset allocations might fail even with a lot of memory available.\n",
> + nodemask_pr_args(&trialcs->mems_allowed));
> + }
> +
> spin_lock_irq(&callback_lock);
> cs->mems_allowed = trialcs->mems_allowed;
> spin_unlock_irq(&callback_lock);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index b37435c..a7e0854 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4914,6 +4914,19 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> if (!ac->preferred_zoneref->zone)
> goto nopage;
>
> + /*
> + * Check for insane configurations where the cpuset doesn't contain
> + * any suitable zone to satisfy the request - e.g. non-movable
> + * GFP_HIGHUSER allocations from MOVABLE nodes only.
> + */
> + if (cpusets_insane_config() && (gfp_mask & __GFP_HARDWALL)) {
> + struct zoneref *z = first_zones_zonelist(ac->zonelist,
> + ac->highest_zoneidx,
> + &cpuset_current_mems_allowed);
> + if (!z->zone)
> + goto nopage;
> + }
> +
> if (alloc_flags & ALLOC_KSWAPD)
> wake_all_kswapds(order, gfp_mask, ac);
The rest looks sensible to me.
--
Michal Hocko
SUSE Labs
