linux-kernel - Re: [PATCH mm v2] vmalloc: back off when the current task is OOM-killed

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Message-Id: <20211007125541.db0f3ff2bdbd8fa7dc1db03d@linux-foundation.org>
Date:   Thu, 7 Oct 2021 12:55:41 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Vasily Averin <vvs@...tuozzo.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel@...nvz.org
Subject: Re: [PATCH mm v2] vmalloc: back off when the current task is
 OOM-killed

On Tue, 5 Oct 2021 16:52:40 +0300 Vasily Averin <vvs@...tuozzo.com> wrote:

> Huge vmalloc allocation on heavy loaded node can lead to a global
> memory shortage. Task called vmalloc can have worst badness and
> be selected by OOM-killer, however taken fatal signal does not
> interrupt allocation cycle. Vmalloc repeat page allocaions
> again and again, exacerbating the crisis and consuming the memory
> freed up by another killed tasks.
> 
> After a successful completion of the allocation procedure, a fatal
> signal will be processed and task will be destroyed finally.
> However it may not release the consumed memory, since the allocated
> object may have a lifetime unrelated to the completed task.
> In the worst case, this can lead to the host will panic
> due to "Out of memory and no killable processes..."
> 
> This patch allows OOM-killer to break vmalloc cycle, makes OOM more
> effective and avoid host panic. It does not check oom condition directly,
> however, and breaks page allocation cycle when fatal signal was received.
> 
> This may trigger some hidden problems, when caller does not handle
> vmalloc failures, or when rollaback after failed vmalloc calls own
> vmallocs inside. However all of these scenarios are incorrect:
> vmalloc does not guarantee successful allocation, it has never been called
> with __GFP_NOFAIL and threfore either should not be used for any rollbacks
> or should handle such errors correctly and not lead to critical
> failures.
> 

This needed a little rework due to
https://lkml.kernel.org/r/20210928121040.2547407-1-chenwandun@huawei.com.
Please check and retest sometime?

--- a/mm/vmalloc.c~vmalloc-back-off-when-the-current-task-is-oom-killed
+++ a/mm/vmalloc.c
@@ -2887,6 +2887,9 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 
 	page = NULL;
 	while (nr_allocated < nr_pages) {
+		if (fatal_signal_pending(current))
+			break;
+
 		if (nid == NUMA_NO_NODE)
 			page = alloc_pages(gfp, order);
 		else
_