Message-ID: <CAHbLzkpMLJtK_ZdQw=pN5TJL_B4vW=jGCJhACxOP0w4QSitUtQ@mail.gmail.com>
Date:   Wed, 18 Aug 2021 11:01:10 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>
Cc:     Oscar Salvador <osalvador@...e.de>, tdmackey@...tter.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Naoya Horiguchi <naoya.horiguchi@....com>
Subject: Re: [PATCH 1/2] mm: hwpoison: don't drop slab caches for offlining
 non-LRU page

On Tue, Aug 17, 2021 at 11:30 PM Naoya Horiguchi
<naoya.horiguchi@...ux.dev> wrote:
>
> On Mon, Aug 16, 2021 at 11:09:08AM -0700, Yang Shi wrote:
> > In the current implementation of soft offline, if non-LRU page is met,
> > all the slab caches will be dropped to free the page then offline.  But
> > if the page is not slab page all the effort is wasted in vain.  Even
> > though it is a slab page, it is not guaranteed the page could be freed
> > at all.
> >
> > However the side effect and cost is quite high.  It does not only drop
> > the slab caches, but also may drop a significant amount of page caches
> > which are associated with inode caches.  It could make the most
> > workingset gone in order to just offline a page.  And the offline is not
> > guaranteed to succeed at all, actually I really doubt the success rate
> > for real life workload.
> >
> > Furthermore the worse consequence is the system may be locked up and
> > unusable since the page cache release may incur huge amount of works
> > queued for memcg release.
> >
> > Actually we ran into such unpleasant case in our production environment.
> > Firstly, the workqueue of memory_failure_work_func is locked up as
> > below:
> >
> > BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 53s!
> > Showing busy workqueues and worker pools:
> > workqueue events: flags=0x0
> >   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=14/256 refcnt=15
> >     in-flight: 409271:memory_failure_work_func
> >     pending: kfree_rcu_work, kfree_rcu_monitor, kfree_rcu_work, rht_deferred_worker, rht_deferred_worker, rht_deferred_worker, rht_deferred_worker, kfree_rcu_work, kfree_rcu_work, kfree_rcu_work, kfree_rcu_work, drain_local_stock, kfree_rcu_work
> > workqueue mm_percpu_wq: flags=0x8
> >   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256 refcnt=2
> >     pending: vmstat_update
> > workqueue cgroup_destroy: flags=0x0
> >   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1 refcnt=12072
> >     pending: css_release_work_fn
> >
> > There were over 12K css_release_work_fn queued, and this caused a few
> > lockups due to the contention of worker pool lock with IRQ disabled, for
> > example:
> >
> > NMI watchdog: Watchdog detected hard LOCKUP on cpu 1
> > Modules linked in: amd64_edac_mod edac_mce_amd crct10dif_pclmul crc32_pclmul ghash_clmulni_intel xt_DSCP iptable_mangle kvm_amd bpfilter vfat fat acpi_ipmi i2c_piix4 usb_storage ipmi_si k10temp i2c_core ipmi_devintf ipmi_msghandler acpi_cpufreq sch_fq_codel xfs libcrc32c crc32c_intel mlx5_core mlxfw nvme xhci_pci ptp nvme_core pps_core xhci_hcd
> > CPU: 1 PID: 205500 Comm: kworker/1:0 Tainted: G             L    5.10.32-t1.el7.twitter.x86_64 #1
> > Hardware name: TYAN F5AMT /z        /S8026GM2NRE-CGN, BIOS V8.030 03/30/2021
> > Workqueue: events memory_failure_work_func
> > RIP: 0010:queued_spin_lock_slowpath+0x41/0x1a0
> > Code: 41 f0 0f ba 2f 08 0f 92 c0 0f b6 c0 c1 e0 08 89 c2 8b 07 30 e4 09 d0 a9 00 01 ff ff 75 1b 85 c0 74 0e 8b 07 84 c0 74 08 f3 90 <8b> 07 84 c0 75 f8 b8 01 00 00 00 66 89 07 c3 f6 c4 01 75 04 c6 47
> > RSP: 0018:ffff9b2ac278f900 EFLAGS: 00000002
> > RAX: 0000000000480101 RBX: ffff8ce98ce71800 RCX: 0000000000000084
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8ce98ce6a140
> > RBP: 00000000000284c8 R08: ffffd7248dcb6808 R09: 0000000000000000
> > R10: 0000000000000003 R11: ffff9b2ac278f9b0 R12: 0000000000000001
> > R13: ffff8cb44dab9c00 R14: ffffffffbd1ce6a0 R15: ffff8cacaa37f068
> > FS:  0000000000000000(0000) GS:ffff8ce98ce40000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fcf6e8cb000 CR3: 0000000a0c60a000 CR4: 0000000000350ee0
> > Call Trace:
> >  __queue_work+0xd6/0x3c0
> >  queue_work_on+0x1c/0x30
> >  uncharge_batch+0x10e/0x110
> >  mem_cgroup_uncharge_list+0x6d/0x80
> >  release_pages+0x37f/0x3f0
> >  __pagevec_release+0x1c/0x50
> >  __invalidate_mapping_pages+0x348/0x380
> >  ? xfs_alloc_buftarg+0xa4/0x120 [xfs]
> >  inode_lru_isolate+0x10a/0x160
> >  ? iput+0x1d0/0x1d0
> >  __list_lru_walk_one+0x7b/0x170
> >  ? iput+0x1d0/0x1d0
> >  list_lru_walk_one+0x4a/0x60
> >  prune_icache_sb+0x37/0x50
> >  super_cache_scan+0x123/0x1a0
> >  do_shrink_slab+0x10c/0x2c0
> >  shrink_slab+0x1f1/0x290
> >  drop_slab_node+0x4d/0x70
> >  soft_offline_page+0x1ac/0x5b0
> >  ? dev_mce_log+0xee/0x110
> >  ? notifier_call_chain+0x39/0x90
> >  memory_failure_work_func+0x6a/0x90
> >  process_one_work+0x19e/0x340
> >  ? process_one_work+0x340/0x340
> >  worker_thread+0x30/0x360
> >  ? process_one_work+0x340/0x340
> >  kthread+0x116/0x130
> >
> > The lockup made the machine is quite unusable.  And it also made the
> > most workingset gone, the reclaimabled slab caches were reduced from 12G
> > to 300MB, the page caches were decreased from 17G to 4G.
> >
> > But the most disappointing thing is all the effort doesn't make the page
> > offline, it just returns:
> >
> > soft_offline: 0x1469f2: unknown non LRU page type 5ffff0000000000 ()
> >
> > It seems the aggressive behavior for non-LRU page didn't pay back, so it
> > doesn't make too much sense to keep it considering the terrible side
> > effect.
> >
> > Reported-by: David Mackey <tdmackey@...tter.com>
> > Cc: Naoya Horiguchi <naoya.horiguchi@....com>
> > Cc: Oscar Salvador <osalvador@...e.de>
> > Signed-off-by: Yang Shi <shy828301@...il.com>
>
> Thank you. I agree with the idea of dropping drop_slab_node() in shake_page(),
> hoping that range-based slab shrinker will be implemented in the future.
>
> This patch conflicts with the patch
> https://lore.kernel.org/linux-mm/20210817053703.2267588-1-naoya.horiguchi@linux.dev/T/#u
> which adds another shake_page(), so could you add the following hunk in your patch?
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 64f8ac969544..7dd2ca665866 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1198,7 +1198,7 @@ static int get_any_page(struct page *p, unsigned long flags)
>                          * page, retry.
>                          */
>                         if (pass++ < 3) {
> -                               shake_page(p, 1);
> +                               shake_page(p);
>                                 goto try_again;
>                         }
>                         goto out;

BTW, a question about the return value with the above patch, will
reply in that thread.

>
>
> Thanks,
> Naoya Horiguchi

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