Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751085AbVKNL2I (ORCPT ); Mon, 14 Nov 2005 06:28:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751086AbVKNL2I (ORCPT ); Mon, 14 Nov 2005 06:28:08 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:14237 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1751085AbVKNL2G (ORCPT ); Mon, 14 Nov 2005 06:28:06 -0500 Subject: Re: [2.6 patch] i386: always use 4k stacks From: Arjan van de Ven To: Jens Axboe Cc: Pierre Ossman , Adrian Bunk , Andrew Morton , linux-kernel@vger.kernel.org In-Reply-To: <20051114112402.GT3699@suse.de> References: <20051114021127.GC5735@stusta.de> <4378650A.1070209@drzeus.cx> <1131964282.2821.11.camel@laptopd505.fenrus.org> <20051114111108.GR3699@suse.de> <1131967167.2821.14.camel@laptopd505.fenrus.org> <20051114112402.GT3699@suse.de> Content-Type: text/plain Date: Mon, 14 Nov 2005 12:27:57 +0100 Message-Id: <1131967678.2821.21.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-Spam-Score: 1.8 (+) X-Spam-Report: SpamAssassin version 3.0.4 on pentafluge.infradead.org summary: Content analysis details: (1.8 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.1 RCVD_IN_SORBS_DUL RBL: SORBS: sent directly from dynamic IP address [213.93.14.173 listed in dnsbl.sorbs.net] 1.7 RCVD_IN_NJABL_DUL RBL: NJABL: dialup sender did non-local SMTP [213.93.14.173 listed in combined.njabl.org] X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1336 Lines: 28 On Mon, 2005-11-14 at 12:24 +0100, Jens Axboe wrote: > > > > not sure; I do know that it very much helps java (many more threads > > possible) and the VM (far less order 1 allocs). In addition the 4Kb > > allocation can be satisfied with the per cpu list of free 4Kb pages, > > while obviously an order 1 cannot and has to go global. > > I realize it has nice advantages in theory, just wondering if anyone has > done a performance analysis of 4kb vs 8kb stacks lately (or at all?). I don't think at least anyone at RH has done any; the functionality gain was already enough for us. One item I missed: in the many-thread cases, you also save a lot of memory that can now be used for pagecache; this won't of course be visible in a microbenchmark but should help system wide. Also in the implementation I don't see any way 4Kb stacks could show up in any benchmarks as negative; there are only 4 or 5 extra instructions in any path, and afaics no cache downsides (in fact the same irq stack memory is now reused for irqs instead of threadstack-du-jour, so less footprint/hotter caches) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/