Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758156AbaDBHq4 (ORCPT ); Wed, 2 Apr 2014 03:46:56 -0400 Received: from mail-wg0-f45.google.com ([74.125.82.45]:34594 "EHLO mail-wg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758035AbaDBHqy (ORCPT ); Wed, 2 Apr 2014 03:46:54 -0400 Date: Wed, 2 Apr 2014 09:46:51 +0200 From: Ingo Molnar To: Shaohua Li Cc: Rik van Riel , Linus Torvalds , Linux Kernel Mailing List , linux-mm , Andrew Morton , Hugh Dickins , Mel Gorman Subject: Re: [PATCH] x86,mm: delay TLB flush after clearing accessed bit Message-ID: <20140402074651.GA22772@gmail.com> References: <20140331113442.0d628362@annuminas.surriel.com> <533AE518.1090705@redhat.com> <533B0603.7040301@redhat.com> <20140402060601.GA31305@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140402060601.GA31305@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Shaohua Li wrote: > On Tue, Apr 01, 2014 at 02:31:31PM -0400, Rik van Riel wrote: > > On 04/01/2014 12:21 PM, Linus Torvalds wrote: > > > On Tue, Apr 1, 2014 at 9:11 AM, Rik van Riel wrote: > > >> > > >> Memory pressure is not necessarily caused by the same process > > >> whose accessed bit we just cleared. Memory pressure may not > > >> even be caused by any process's virtual memory at all, but it > > >> could be caused by the page cache. > > > > > > If we have that much memory pressure on the page cache without having > > > any memory pressure on the actual VM space, then the swap-out activity > > > will never be an issue anyway. > > > > > > IOW, I think all these scenarios are made-up. I'd much rather go for > > > simpler implementation, and make things more complex only in the > > > presence of numbers. Of which we have none. > > > > We've been bitten by the lack of a properly tracked accessed > > bit before, but admittedly that was with the KVM code and EPT. > > > > I'll add my Acked-by: to Shaohua's original patch then, and > > will keep my eyes open for any problems that may or may not > > materialize... > > > > Shaohua? > > I'd agree to choose the simple implementation at current stage and check if > there are problems really. > > Andrew, > can you please pick up my orginal patch "x86: clearing access bit don't > flush tlb" (with Rik's Ack)? Or I can resend it if you preferred. Please resend it so I can pick it up for this cycle, that approach obviously looks good. Thanks, Ingo -- 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/