From: Michal Hocko <mhocko@suse.cz>
To: Alex Bligh <alex@alex.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Local DoS through write heavy I/O on CFQ & Deadline
Date: Fri, 12 Oct 2012 15:30:45 +0200 [thread overview]
Message-ID: <20121012133044.GA10115@dhcp22.suse.cz> (raw)
In-Reply-To: <0B138F62-16BF-4295-9AD9-64C0BB39FCE2@alex.org.uk>
On Thu 11-10-12 13:23:32, Alex Bligh wrote:
> We have noticed significant I/O scheduling issues on both the CFQ and the
> deadline scheduler where a non-root user can starve any other process of
> any I/O for minutes at a time. The problem is more serious using CFQ but is
> still an effective local DoS vector using Deadline.
>
> A simple way to generate the problem is:
>
> dd if=/dev/zero of=- bs=1M count=50000 | dd if=- of=myfile bs=1M count=50000
>
[...]
>
> Full info, including logs and scripts can be found at:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1064521
You seem to have 8G of RAM and dirty_ratio=20 resp.
dirty_background_ratio=10 which means that 1.5G worth of dirty data
until writer gets throttled which is a lot. Background writeback starts
at 800M which is probably not sufficient as well. Have you tried to set
dirty_bytes at a reasonable value (wrt. to your storage)?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2012-10-12 13:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-11 12:23 Local DoS through write heavy I/O on CFQ & Deadline Alex Bligh
2012-10-11 13:46 ` Alan Cox
2012-10-12 12:57 ` Alex Bligh
2012-10-12 13:30 ` Michal Hocko [this message]
2012-10-12 14:48 ` Alex Bligh
2012-10-12 14:58 ` Michal Hocko
2012-10-12 16:29 ` Alex Bligh
2012-10-13 13:53 ` Hillf Danton
2012-10-13 19:33 ` Alex Bligh
2012-10-14 2:43 ` Hillf Danton
2012-10-15 8:17 ` Michal Hocko
2012-10-18 21:28 ` Jan Kara
2012-10-18 22:13 ` Chris Friesen
2012-10-18 22:24 ` Jan Kara
2012-10-14 21:17 ` Dave Chinner
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