From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752813AbaI3QHq (ORCPT ); Tue, 30 Sep 2014 12:07:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50656 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751474AbaI3QHp (ORCPT ); Tue, 30 Sep 2014 12:07:45 -0400 Date: Tue, 30 Sep 2014 12:07:29 -0400 From: Dave Jones To: Rik van Riel Cc: Linus Torvalds , Al Viro , Linux Kernel , Ingo Molnar , Michel Lespinasse Subject: Re: pipe/page fault oddness. Message-ID: <20140930160729.GB15903@redhat.com> Mail-Followup-To: Dave Jones , Rik van Riel , Linus Torvalds , Al Viro , Linux Kernel , Ingo Molnar , Michel Lespinasse References: <20140930033327.GA14558@redhat.com> <20140930043309.GA16196@redhat.com> <542AD43A.90706@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <542AD43A.90706@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 30, 2014 at 12:03:06PM -0400, Rik van Riel wrote: > > What kind of CPU is the problematic machine? There was some > > question about just how architectural the whole "TLB entry causing > > a page fault gets invalidated automatically" really is. > > Intel people told me at the time that the guarantee was architectural. > I don't know whether other x86 manufacturers know this... > > Doing a local tlb flush from ptep_set_access_flags seems appropriate, > if that is indeed the issue. > > On the other hand, do_wp_page does not seem to do a tlb flush when > the old page is reused, so CPUs do get rid of inappropriate TLB > entries. We would have noticed do_wp_page not working right :) The puzzling thing is we've had that code change for two years without issue. This isn't a new machine, so why would it only be showing up bad effects now ? Dave