From: Andrew Morton <akpm@linux-foundation.org>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: linux-kernel@vger.kernel.org, mhocko@suse.cz,
Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
linux-mm@kvack.org (open list:MEMORY MANAGEMENT)
Subject: Re: [PATCH 1/2] mm: free large amount of 0-order pages in workqueue
Date: Tue, 31 Mar 2015 15:31:27 -0700 [thread overview]
Message-ID: <20150331153127.2eb8cc2f04c742dde7a8c96c@linux-foundation.org> (raw)
In-Reply-To: <1427839895-16434-1-git-send-email-sasha.levin@oracle.com>
On Tue, 31 Mar 2015 18:11:32 -0400 Sasha Levin <sasha.levin@oracle.com> wrote:
> Freeing pages became a rather costly operation, specially when multiple debug
> options are enabled. This causes hangs when an attempt to free a large amount
> of 0-order is made. Two examples are vfree()ing large block of memory, and
> punching a hole in a shmem filesystem.
>
> To avoid that, move any free operations that involve batching pages into a
> list to a workqueue handler where they could be freed later.
eek.
__free_pages() is going to be a hot path for someone - it has 500+
callsites.
And this patch might cause problems for rt_prio() tasks which run for a
long time, starving out the workqueue thread. And probably other stuff
I didn't think of...
What whacky debug option is actually causing this? Full-page poisoning?
Stick a cond_resched() in __vunmap() ;)
prev parent reply other threads:[~2015-03-31 22:31 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-31 22:11 [PATCH 1/2] mm: free large amount of 0-order pages in workqueue Sasha Levin
2015-03-31 22:11 ` [PATCH 2/2] mm: __free_pages batch up 0-order pages for freeing Sasha Levin
2015-04-01 12:48 ` Rasmus Villemoes
2015-03-31 22:31 ` Andrew Morton [this message]
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