linux-kernel - Re: [PATCH][RFC] slub: increasing order reduces memory usage of some key caches

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

Message-Id: <1216288113.3061.2.camel@castor.localdomain>
Date:	Thu, 17 Jul 2008 10:48:33 +0100
From:	Richard Kennedy <richard@....demon.co.uk>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	penberg@...helsinki.fi, mpm@...enic.com,
	linux-mm <linux-mm@...ck.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][RFC] slub: increasing order reduces memory usage of
	some key caches


On Wed, 2008-07-16 at 20:52 +0100, Mel Gorman wrote:
> On (16/07/08 08:21), Christoph Lameter didst pronounce:
> > Richard Kennedy wrote:
> > 
> > 
> > > on my amd64 3 gb ram desktop typical numbers :-
> > > 
> > > [kernel,objects,pages/slab,slabs,total pages,diff]
> > > radix_tree_node
> > > 2.6.26 33922,2,2423 	4846
> > > +patch 33541,4,1165	4660,-186
> > > dentry
> > > 2.6.26	82136,1,4323	4323
> > > +patch	79482,2,2038	4076,-247
> > > the extra dentries would use 136 pages but that still leaves a saving of
> > > 111 pages.
> > 
> > Good numbers....
> > 
> 
> Indeed. clearly internal fragmentation is a problem.
> 
> > > Can anyone suggest any other tests that would be useful to run?
> > > & Is there any way to measure what impact this is having on
> > > fragmentation?
> > 
> > Mel would be able to tell you that but I think we better figure out what went wrong first.
> > 
> 
> For internal fragmentation, there is this crappy script:
> http://www.csn.ul.ie/~mel/intfrag_stat
> 
> run it as intfrag_stat -a and it should tell you what precentage of
> memory is being wasted for dentries. The patch should show a difference
> for the dentries.
> 
> How it would affect external fragmentation is harder to guess. It will
> put more pressure for high-order allocations but at a glance, dentries
> are using GFP_KERNEL so it should not be a major problem.
> /proc/pagetypeinfo is the file to watch. If the count for "reclaimable"
> arenas is higher and climbing over time, it will indiate that external
> fragmentation would eventually become a problem.
> 
Mel,
Thanks for the info & the script. I'll give it a try & see what we get.
Richard


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