From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 7 Jun 2000 14:41:02 +0100 From: "Stephen C. Tweedie" Subject: Re: journaling & VM (was: Re: reiserfs being part of the kernel: it'snot just the code) Message-ID: <20000607144102.F30951@redhat.com> References: <20000607121555.G29432@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ; from riel@conectiva.com.br on Wed, Jun 07, 2000 at 10:23:35AM -0300 Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: "Stephen C. Tweedie" , Hans Reiser , "Quintela Carreira Juan J." , bert hubert , linux-kernel@vger.rutgers.edu, Chris Mason , linux-mm@kvack.org, Alexander Zarochentcev List-ID: Hi, On Wed, Jun 07, 2000 at 10:23:35AM -0300, Rik van Riel wrote: > > > > There is no need for subcaches at all if all of the pages can be > > represented on the page cache LRU lists. That would certainly > > make balancing between caches easier. > > Wouldn't this mean we could end up with an LRU cache full of > unfreeable pages? Rik, we need the VM to track dirty pages anyway, precisely so that we can obtain some degree of write throttling to avoid having the whole of memory full of dirty pages. If we get short of memory, we really need to start flushing dirty pages to disk independently of the task of finding free pages. Interrupts cannot wait for IO to complete --- they need the free memory immediately. Page cleaning needs to be identified as a very different job from page reclaiming. Whatever list we use to track dirty pages can equally well be used for callbacks to transactional filesystems. > This could get particularly nasty when we have a VM with > active / inactive / scavenge lists... (like what I'm working > on now) Right, we definitely need a better distinction between different lists and different types of page activity before we can do this. > Question is, are the filesystems ready to play this game? With an address_space callback, yes --- ext3 can certainly find a transaction covering a given page. I'd imagine reiserfs can do something similar, but even if not, it's not important if the filesystem can't do its lookup by page. The mere fact that the filesystem sees the VM trying to scavenge dirty pages can trigger it into starting to flush its oldest transactions, and that is something that all filesystems should be able to do easily. Cheers, Stephen -- 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.eu.org/Linux-MM/