Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992864AbWJTVtF (ORCPT ); Fri, 20 Oct 2006 17:49:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2992792AbWJTVtC (ORCPT ); Fri, 20 Oct 2006 17:49:02 -0400 Received: from ftp.linux-mips.org ([194.74.144.162]:42449 "EHLO ftp.linux-mips.org") by vger.kernel.org with ESMTP id S2992803AbWJTVs7 (ORCPT ); Fri, 20 Oct 2006 17:48:59 -0400 Date: Fri, 20 Oct 2006 22:49:16 +0100 From: Ralf Baechle To: Linus Torvalds Cc: David Miller , nickpiggin@yahoo.com.au, Andrew Morton , Linux Kernel Mailing List , anemo@mba.ocn.ne.jp, linux-arch@vger.kernel.org, Martin Schwidefsky , James Bottomley Subject: Re: [PATCH 1/3] Fix COW D-cache aliasing on fork Message-ID: <20061020214916.GA27810@linux-mips.org> References: <20061020.123635.95058911.davem@davemloft.net> <20061020.125851.115909797.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1332 Lines: 32 On Fri, Oct 20, 2006 at 01:10:59PM -0700, Linus Torvalds wrote: > Ok, this sounds sane. > > What should we do about this? How does this patch look to people? > > (Totally untested, and I'm not sure we should even do that whole > "oldmm->mm_users" test, but I'm throwing it out here for discussion, in > case it matters for performance. The second D$ flush should obviously be > unnecessary for the common unthreaded case, which is why none of this has > mattered historically, I think). > > Comments? We need ARM, MIPS, sparc and S390 at the very least to sign off > on this, and somebody to write a nice explanation for the changelog (and > preferably do this through -mm too). As a minimal solution your patch would work for MIPS but performance would be suboptimal. With my D-cache alias series applied the flush_cache_mm() in dup_mmap() becomes entirely redundant. When I delete the call (not part of my patchset) it means 12% faster fork. But I'm not proposing this for 2.6.19. Note this does not make the flush_cache_mm() on process termination redundant ... Ralf - 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/