Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752640AbdGRRGl (ORCPT ); Tue, 18 Jul 2017 13:06:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:47536 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751603AbdGRRGh (ORCPT ); Tue, 18 Jul 2017 13:06:37 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2761B22C91 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org MIME-Version: 1.0 In-Reply-To: <20170718085341.nlt35dph4oukb4tc@gmail.com> References: <20170705121807.GF4941@worktop> <20170705170219.ogjnswef3ufgeklz@hirez.programming.kicks-ass.net> <20170718085341.nlt35dph4oukb4tc@gmail.com> From: Andy Lutomirski Date: Tue, 18 Jul 2017 10:06:15 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4 10/10] x86/mm: Try to preserve old TLB entries using PCID To: Ingo Molnar Cc: Peter Zijlstra , Andy Lutomirski , X86 ML , "linux-kernel@vger.kernel.org" , Borislav Petkov , Linus Torvalds , Andrew Morton , Mel Gorman , "linux-mm@kvack.org" , Nadav Amit , Rik van Riel , Dave Hansen , Arjan van de Ven Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1703 Lines: 46 On Tue, Jul 18, 2017 at 1:53 AM, Ingo Molnar wrote: > > * Peter Zijlstra wrote: > >> On Wed, Jul 05, 2017 at 09:04:39AM -0700, Andy Lutomirski wrote: >> > On Wed, Jul 5, 2017 at 5:18 AM, Peter Zijlstra wrote: >> > > On Thu, Jun 29, 2017 at 08:53:22AM -0700, Andy Lutomirski wrote: >> > >> @@ -104,18 +140,20 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, >> > >> >> > >> /* Resume remote flushes and then read tlb_gen. */ >> > >> cpumask_set_cpu(cpu, mm_cpumask(next)); >> > > >> > > Barriers should have a comment... what is being ordered here against >> > > what? >> > >> > How's this comment? >> > >> > /* >> > * Resume remote flushes and then read tlb_gen. We need to do >> > * it in this order: any inc_mm_tlb_gen() caller that writes a >> > * larger tlb_gen than we read here must see our cpu set in >> > * mm_cpumask() so that it will know to flush us. The barrier >> > * here synchronizes with inc_mm_tlb_gen(). >> > */ >> >> Slightly confusing, you mean this, right? >> >> >> cpumask_set_cpu(cpu, mm_cpumask()); inc_mm_tlb_gen(); >> >> MB MB >> >> next_tlb_gen = atomic64_read(&next->context.tlb_gen); flush_tlb_others(mm_cpumask()); >> >> >> which seems to make sense. > > Btw., I'll wait for a v5 iteration before applying this last patch to tip:x86/mm. I'll send it shortly. I think I'll also add a patch to factor out the flush calls a bit more to prepare for Mel's upcoming fix. > > Thanks, > > Ingo