Subject: Re: [PATCH] vmscan: do not throttle kthreads due to too_many_isolated
To: Vladimir Davydov <vdavydov@virtuozzo.com>,
        Andrew Morton <akpm@linux-foundation.org>
References: <1448465801-3280-1-git-send-email-vdavydov@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@kernel.org>,
        Mel Gorman <mgorman@techsingularity.net>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
From: Vlastimil Babka <vbabka@suse.cz>
Message-ID: <5655D789.80201@suse.cz>
Date: Wed, 25 Nov 2015 16:45:13 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.3.0
MIME-Version: 1.0
In-Reply-To: <1448465801-3280-1-git-send-email-vdavydov@virtuozzo.com>
Content-Type: text/plain; charset=iso-8859-2
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 783
Lines: 15

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? PF_KTHREAD looks like a big hammer to me that
will solve only one potential problem...

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/