From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH][RFC] slub: increasing order reduces memory usage of some key caches From: Richard Kennedy In-Reply-To: <20080716195237.GA9127@csn.ul.ie> References: <1216211371.3122.46.camel@castor.localdomain> <487DF5D4.9070101@linux-foundation.org> <20080716195237.GA9127@csn.ul.ie> Content-Type: text/plain Date: Thu, 17 Jul 2008 10:48:33 +0100 Message-Id: <1216288113.3061.2.camel@castor.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Mel Gorman Cc: Christoph Lameter , penberg@cs.helsinki.fi, mpm@selenic.com, linux-mm , lkml List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org