From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 17 Jul 2001 04:55:34 +0200 (CEST) From: Mike Galbraith Subject: Re: [PATCH] Separate global/perzone inactive/free shortage In-Reply-To: <20010716193033.H28023@redhat.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: "Stephen C. Tweedie" Cc: Marcelo Tosatti , Rik van Riel , Dirk Wetter , linux-mm@kvack.org List-ID: On Mon, 16 Jul 2001, Stephen C. Tweedie wrote: > Hi, > > On Mon, Jul 16, 2001 at 05:44:17PM +0200, Mike Galbraith wrote: > > > > Why not just round-robin between the eligible zones when allocating, > > > biasing each zone based on size? > > > What prevents this from happening, and lets make ZONE_DINKY _really_ > > dinky just for the sake of argument. ZONE_DINKY will have say 4 pages, > > one for active, dirty, clean and free. Balanced is 2 dirty and 2 free, > > or 1 free, 1 clean and 1 dirty. 2 tasks are running, and both are giant > > economy size, with very nearly 2gig of vm allocated each. > > > > ZONE_DINKY, ZONE_BIG, and ZONE_MONDO are all fully engaged and under > > pressure. ZONE_DINKY gets aged/laundered such that it is in balance. > > Task A is using 1 ZONE_DINKY page. Task B requests a page to do pagein, > > and reclaims a page from ZONE_DINKY because there's only 1 free page. > > We are back to inactive shortage instantly, so we have to walk 4gig of > > vm looking for one ZONE_DINKY page to activate/age/deactivate. During > > the aging process, any other in use page from that zone is fair game. > > Agreed, but in that sort of case, if we have (say) close 1GB in > ZONE_NORMAL and 16MB in ZONE_DMA, then only one allocation in 64 will > even _try_ to allocate from the DMA zone. Replace the DMA zone with a > hypothetical DINKY 4-page zone and it goes down to one allocation in > 65536. You don't reduce the cost of a DINKY allocation, but you > reduce the change that such an allocation will happen. > > The balanced round-robin still seems like a helpful next step here > even if it doesn't cure all the balance problems immediately. Yes, this should mitigate the effect. I think something will still end up having to be done about the search time though. Dirk's case seems to be the pathalogical one. -Mike -- 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/