Re: [PATCH v2] mm: memcg: update memcg OOM messages on cgroup2

[Roman Gushchin <guro@fb.com>]

On Mon, Aug 06, 2018 at 09:15:29AM -0700, Tejun Heo wrote:
> mem_cgroup_print_oom_info() currently prints the same info for cgroup1
> and cgroup2 OOMs.  It doesn't make much sense on cgroup2, which
> doesn't use memsw or separate kmem accounting - the information
> reported is both superflous and insufficient.  This patch updates the
> memcg OOM messages on cgroup2 so that
> 
> * It prints memory and swap usages and limits used on cgroup2.
> 
> * It shows the same information as memory.stat.
> 
> I took out the recursive printing for cgroup2 because the amount of
> output could be a lot and the benefits aren't clear.  An example dump
> follows.
> 
> [   40.854197] stress invoked oom-killer: gfp_mask=0x6000c0(GFP_KERNEL), nodemask=(null), order=0, oo0
> [   40.855239] stress cpuset=/ mems_allowed=0
> [   40.855665] CPU: 6 PID: 1990 Comm: stress Not tainted 4.18.0-rc7-work+ #281
> [   40.856260] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
> [   40.857000] Call Trace:
> [   40.857222]  dump_stack+0x5e/0x8b
> [   40.857517]  dump_header+0x74/0x2fc
> [   40.859106]  oom_kill_process+0x225/0x490
> [   40.859449]  out_of_memory+0x111/0x530
> [   40.859780]  mem_cgroup_out_of_memory+0x4b/0x80
> [   40.860161]  mem_cgroup_oom_synchronize+0x3ff/0x450
> [   40.861334]  pagefault_out_of_memory+0x2f/0x74
> [   40.861718]  __do_page_fault+0x3de/0x460
> [   40.862347]  page_fault+0x1e/0x30
> [   40.862636] RIP: 0033:0x5566cd5aadd0
> [   40.862940] Code: 0f 84 3c 02 00 00 8b 54 24 0c 31 c0 85 d2 0f 94 c0 89 04 24 41 83 fd 02 0f 8f f6
> [   40.864558] RSP: 002b:00007ffd979ced40 EFLAGS: 00010206
> [   40.865005] RAX: 0000000001f4f000 RBX: 00007f3a397d8010 RCX: 00007f3a397d8010
> [   40.865615] RDX: 0000000000000000 RSI: 0000000004001000 RDI: 0000000000000000
> [   40.866220] RBP: 00005566cd5abbb4 R08: 00000000ffffffff R09: 0000000000000000
> [   40.866845] R10: 0000000000000022 R11: 0000000000000246 R12: ffffffffffffffff
> [   40.867452] R13: 0000000000000002 R14: 0000000000001000 R15: 0000000004000000
> [   40.868091] Task in /test-cgroup killed as a result of limit of /test-cgroup
> [   40.868726] memory 33554432 (max 33554432)
> [   40.869096] swap 0
> [   40.869280] anon 32845824
> [   40.869519] file 0
> [   40.869730] kernel_stack 0
> [   40.869966] slab 163840
> [   40.870191] sock 0
> [   40.870374] shmem 0
> [   40.870566] file_mapped 0
> [   40.870801] file_dirty 0
> [   40.871039] file_writeback 0
> [   40.871292] inactive_anon 0
> [   40.871542] active_anon 32944128
> [   40.871821] inactive_file 0
> [   40.872077] active_file 0
> [   40.872309] unevictable 0
> [   40.872543] slab_reclaimable 0
> [   40.872806] slab_unreclaimable 163840
> [   40.873136] pgfault 8085
> [   40.873358] pgmajfault 0
> [   40.873589] pgrefill 0
> [   40.873800] pgscan 0
> [   40.873991] pgsteal 0
> [   40.874202] pgactivate 0
> [   40.874424] pgdeactivate 0
> [   40.874663] pglazyfree 0
> [   40.874881] pglazyfreed 0
> [   40.875121] workingset_refault 0
> [   40.875401] workingset_activate 0
> [   40.875689] workingset_nodereclaim 0
> [   40.875996] [ pid ]   uid  tgid total_vm      rss pgtables_bytes swapents oom_score_adj name
> [   40.876789] [ 1969]     0  1969     5121      970    86016        0             0 bash
> [   40.877546] [ 1989]     0  1989     1998      260    61440        0             0 stress
> [   40.878256] [ 1990]     0  1990    18383     8055   126976        0             0 stress
> [   40.878955] Memory cgroup out of memory: Kill process 1990 (stress) score 987 or sacrifice child
> [   40.879803] Killed process 1990 (stress) total-vm:73532kB, anon-rss:32008kB, file-rss:212kB, shmemB
> 
> v2: Updated commit message to include an example dump as suggested by
>     Roman.

Looks good to me!
I'd still drop the mm events output, but I'm fine with it too.

Acked-by: Roman Gushchin <guro@fb.com>

Thank you!