From: Vladimir Davydov <vdavydov@virtuozzo.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] vmscan: do not throttle kthreads due to too_many_isolated
Date: Wed, 25 Nov 2015 19:27:57 +0300 [thread overview]
Message-ID: <20151125162756.GJ29014@esperanza> (raw)
In-Reply-To: <5655D789.80201@suse.cz>
On Wed, Nov 25, 2015 at 04:45:13PM +0100, Vlastimil Babka wrote:
> On 11/25/2015 04:36 PM, Vladimir Davydov wrote:
> > Block device drivers often hand off io request processing to kernel
> > threads (example: device mapper). If such a thread calls kmalloc, it can
> > dive into direct reclaim path and end up waiting for too_many_isolated
> > to return false, blocking writeback. This can lead to a dead lock if the
>
> Shouldn't such allocation lack __GFP_IO to prevent this and other kinds of
> deadlocks? And/or have mempools?
Not necessarily. loopback is an example: it can call
grab_cache_write_begin -> add_to_page_cache_lru with GFP_KERNEL.
> PF_KTHREAD looks like a big hammer to me that will solve only one
> potential problem...
This problem can result in processes hanging forever. Any ideas how this
could be fixed in a better way?
Thanks,
Vladimir
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next prev parent reply other threads:[~2015-11-25 16:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-25 15:36 Vladimir Davydov
2015-11-25 15:45 ` Vlastimil Babka
2015-11-25 16:27 ` Vladimir Davydov [this message]
2015-11-26 8:16 ` Vladimir Davydov
2015-11-27 12:50 ` Michal Hocko
2015-11-27 13:40 ` Vladimir Davydov
2015-11-27 15:01 ` Michal Hocko
2015-12-01 11:25 ` Vladimir Davydov
2015-12-02 13:52 ` Michal Hocko
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