From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f175.google.com (mail-we0-f175.google.com [74.125.82.175]) by kanga.kvack.org (Postfix) with ESMTP id 8B7256B0036 for ; Tue, 1 Apr 2014 14:31:43 -0400 (EDT) Received: by mail-we0-f175.google.com with SMTP id q58so6771536wes.34 for ; Tue, 01 Apr 2014 11:31:42 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTP id fv2si10336855wib.104.2014.04.01.11.31.41 for ; Tue, 01 Apr 2014 11:31:42 -0700 (PDT) Message-ID: <533B0603.7040301@redhat.com> Date: Tue, 01 Apr 2014 14:31:31 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH] x86,mm: delay TLB flush after clearing accessed bit References: <20140331113442.0d628362@annuminas.surriel.com> <533AE518.1090705@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Linux Kernel Mailing List , linux-mm , shli@kernel.org, Andrew Morton , Ingo Molnar , Hugh Dickins , Mel Gorman 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? -- All rights reversed -- 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