netdev - Re: [PATCH 00/13] Swap-over-NBD without deadlocking

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20110428134235.GW4658@suse.de>
Date:	Thu, 28 Apr 2011 14:42:35 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Pavel Machek <pavel@....cz>
Cc:	Linux-MM <linux-mm@...ck.org>,
	Linux-Netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>, Neil Brown <neilb@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 00/13] Swap-over-NBD without deadlocking

On Thu, Apr 28, 2011 at 03:31:55PM +0200, Pavel Machek wrote:
> Hi!
> 
> 
> > For testing swap-over-NBD, a machine was booted with 2G of RAM with a
> > swapfile backed by NBD. 16*NUM_CPU processes were started that create
> > anonymous memory mappings and read them linearly in a loop. The total
> > size of the mappings were 4*PHYSICAL_MEMORY to use swap heavily under
> > memory pressure. Without the patches, the machine locks up within
> > minutes and runs to completion with them applied.
> > 
> > Comments?
> 
> Nice!
> 
> It  is easy to see why swapping needs these fixes, but... dirty memory
> writeout is used for memory clearing, too. Are same changes neccessary
> to make that safe?
> 

Dirty page limiting covers the MAP_SHARED cases and are already
throttled approprately.

> (Perhaps raise 'max dirty %' for testing?)

Stress testing passed for dirty ratios of 40% at least. Maybe it would
cause issues when raised to nearly 100% but I don't think that is a
particularly interesting use case.

-- 
Mel Gorman
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html