From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 944FF6B0044 for ; Thu, 22 Jan 2009 18:14:11 -0500 (EST) Date: Fri, 23 Jan 2009 00:13:58 +0100 From: Ingo Molnar Subject: Re: [PATCH 2.6.28 1/2] memory: improve find_vma Message-ID: <20090122231358.GA27033@elte.hu> References: <8c5a844a0901220851g1c21169al4452825564487b9a@mail.gmail.com> <8c5a844a0901221500m7af8ff45v169b6523ad9d7ad3@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8c5a844a0901221500m7af8ff45v169b6523ad9d7ad3@mail.gmail.com> Sender: owner-linux-mm@kvack.org To: Daniel Lowengrub Cc: Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: * Daniel Lowengrub wrote: > On Thu, Jan 22, 2009 at 7:22 PM, Hugh Dickins wrote: > > Do you have some performance figures to support this patch? > > Some of the lmbench tests may be appropriate. > > > > The thing is, expanding vm_area_struct to include another pointer > > will have its own cost, which may well outweigh the efficiency > > (in one particular case) which you're adding. Expanding mm_struct > > for this would be much more palatable, but I don't think that flies. > > > > And it seems a little greedy to require both an rbtree and a doubly > > linked list for working our way around the vmas. > > > > I suspect that originally your enhancement would only have hit when > > extending the stack: which I guess isn't enough to justify the cost. > > But it could well be that unmapped area handling has grown more > > complex down the years, and you get some hits now from that. > > > Thanks for the reply. > I ran an lmbench test on the 2.6.28 kernel and on the same kernel > after applying the patch. Here's a portion of the results with the > format of > test : standard kernel / kernel after patch > > Simple syscall: 0.7419 / 0.4244 microseconds > Simple read: 1.2071 / 0.7270 microseconds there must be a significant measurement mistake here: none of your patches affect the 'simple syscall' path, nor the sys_read() path. Ingo -- 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