From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 26 Jul 2007 03:38:09 -0700 From: Andrew Morton Subject: Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23] Message-Id: <20070726033809.c1691bb0.akpm@linux-foundation.org> In-Reply-To: <20070726102730.GA31894@elte.hu> References: <2c0942db0707232153j3670ef31kae3907dff1a24cb7@mail.gmail.com> <46A58B49.3050508@yahoo.com.au> <2c0942db0707240915h56e007e3l9110e24a065f2e73@mail.gmail.com> <46A6CC56.6040307@yahoo.com.au> <46A85D95.509@kingswood-consulting.co.uk> <20070726092025.GA9157@elte.hu> <20070726023401.f6a2fbdf.akpm@linux-foundation.org> <20070726094024.GA15583@elte.hu> <20070726030902.02f5eab0.akpm@linux-foundation.org> <20070726102730.GA31894@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Ingo Molnar Cc: Frank Kingswood , Andi Kleen , Nick Piggin , Ray Lee , Jesper Juhl , ck list , Paul Jackson , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Thu, 26 Jul 2007 12:27:30 +0200 Ingo Molnar wrote: > > * Andrew Morton wrote: > > > > > > ( we _do_ want to baloon the dentry cache otherwise - for things like > > > > > "find" - having a fast VFS is important. But known-use-once things > > > > > like the daily updatedb job can clearly be annotated properly. ) > > > > > > > > Mutter. /proc/sys/vm/vfs_cache_pressure has been there for what, > > > > three years? Are any distros raising it during the updatedb run yet? > > > > > > but ... that's system-wide, and the 'dont baloon the dcache' is only a > > > property of updatedb. > > > > Sure, but it's practical, isn't it? Who runs (and cares about) > > vfs-intensive workloads during their wee-small-hours updatedb run? > > there's another side-effect: it likely results in the zapping of > thousands of dentries that were cached nicely before. So we might > exchange 'all my apps are swapped out' experience with 'all file access > is slow'. The latter is _probably_ still an improvement over the > balooning, but i'm not sure. Yup. Nobody has begun to think about preserving dcache/icache across load shifts yet, afaik. Hard. > What we _really_ want is an updatedb that > does not disturb the dcache. Well. Hopefully this time next year you can prep a 16MB container and toss your updatedb inside that. Maybe set its peak disk bandwidth utilisation too. However that won't work ;) because I don't think anyone is looking at containerisation of vfs cache memory yet. Perhaps full-on openvz has it, dunno. But updatedb is a special case, because it is so vfs-intensive. For lots of other workloads (those which use heaps of pagecache), resource management via containerisation will work nicely. -- 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