From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx182.postini.com [74.125.245.182]) by kanga.kvack.org (Postfix) with SMTP id C4A9E6B0072 for ; Fri, 26 Oct 2012 14:41:38 -0400 (EDT) Received: by mail-wi0-f173.google.com with SMTP id hm4so567732wib.8 for ; Fri, 26 Oct 2012 11:41:37 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <508AD2FF.5020306@redhat.com> References: <20121025121617.617683848@chello.nl> <20121025124832.840241082@chello.nl> <5089F5B5.1050206@redhat.com> <508A0A0D.4090001@redhat.com> <508ACE6E.8060303@redhat.com> <508AD2FF.5020306@redhat.com> From: Linus Torvalds Date: Fri, 26 Oct 2012 11:41:17 -0700 Message-ID: Subject: Re: [PATCH 05/31] x86/mm: Reduce tlb flushes from ptep_set_access_flags() Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Michel Lespinasse , Peter Zijlstra , Andrea Arcangeli , Mel Gorman , Johannes Weiner , Thomas Gleixner , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar On Fri, Oct 26, 2012 at 11:14 AM, Rik van Riel wrote: > > I suspect the next context switch would flush out the TLB, > making it a slowdown, not a lockup. Common case, yes. But the page fault might happen in kernel space (due to a "put_user()" call, say), and with CONFIG_PREEMPT=n. Sure, put_user() is always done in a context where blocking (and scheduling) is legal, but that doesn't necessarily equate scheduling actually happening. If we're returning to kernel space and don't have any IO, it might never happen. Anyway, I suspect such behavior it's almost impossible to trigger. Which would just make it rather hard to find. Linus -- 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