From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4549C433E0 for ; Tue, 16 Jun 2020 16:35:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A62DD208B3 for ; Tue, 16 Jun 2020 16:35:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="C58ODwXu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730385AbgFPQfR (ORCPT ); Tue, 16 Jun 2020 12:35:17 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:32389 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729912AbgFPQfQ (ORCPT ); Tue, 16 Jun 2020 12:35:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592325315; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ORHnGJFA6Z19L1N7yd7kPFx1/z/PnVDRBNvmZJMNqEQ=; b=C58ODwXuEakej8S2vZBMO9sREEvmAah9xtwU9piCSyGunyo6hn6njjwk4YeuiuC0ZzlTDT rW3IFulau/nfbkH3YlGN0cvpyMF4mxRIQk9PS6buVNrhGaZTGImISkdkjyvqKDRofESlzm Mm9Ul/0NBmlrfJ+UlJQp/+6jZgs/T54= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-465-gH-oggDdPRa8ev6uGsQkRg-1; Tue, 16 Jun 2020 12:35:13 -0400 X-MC-Unique: gH-oggDdPRa8ev6uGsQkRg-1 Received: by mail-qk1-f197.google.com with SMTP id a6so17244240qka.9 for ; Tue, 16 Jun 2020 09:35:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=ORHnGJFA6Z19L1N7yd7kPFx1/z/PnVDRBNvmZJMNqEQ=; b=Ppf43pY8FhNXVoFFy29EQPp/XX9m9VFXgWjpougSDfdDmqB+hljxOFovGBdCDvA4fC kQtXGenfKFSzyscrtJthGFDbmZA/HlpRfne/NmIXnmT+OHjfqhrwmCV717+Cmr6Slqa4 R0yvHU5ZcIAcTQixSOSJx4mdIhcisYXkvlGpPIyUVxGXTIb1o2mygFiJIfE+L7KmA45C IKywUgM6oUOzD7vi9tmhCUv/PZdUpF2ckET2UsNMbhgNn6V/T6A35JY9mEQ3OKfR/tzb XtScDv//TOZQaJLh/4mPjcv/eMEf2k5fvUgjCS5zU45crVPer4aXfNlvBloTZO6rRv1J zfjg== X-Gm-Message-State: AOAM532aHbo0HSmAh/XvimKrbQzjeUu2RTsfKjXAcL4HyJuiTGaLdHmz +1zBxcLpSAznsnWp0Z8ENWSvfE2CzhLpqhJbaELN0LNK7/+aPtRo/xYrymMZVmJQNwcgGGQeSY3 qRH9kLMEcJdyKyTNhWAmlshAP X-Received: by 2002:a37:9587:: with SMTP id x129mr21560261qkd.184.1592325312798; Tue, 16 Jun 2020 09:35:12 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxFtYGitcStKhm9rXFtngsYzszPm1k1N+2h9Oc/swRH+scEB+KPGSxp8+t3TKRkUXSpqa15Pg== X-Received: by 2002:a37:9587:: with SMTP id x129mr21560236qkd.184.1592325312498; Tue, 16 Jun 2020 09:35:12 -0700 (PDT) Received: from xz-x1 ([2607:9880:19c0:32::2]) by smtp.gmail.com with ESMTPSA id b24sm14336505qkj.0.2020.06.16.09.35.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jun 2020 09:35:11 -0700 (PDT) Date: Tue, 16 Jun 2020 12:35:10 -0400 From: Peter Xu To: Alexander Gordeev Cc: linux-kernel@vger.kernel.org, Gerald Schaefer , Andrew Morton , Linus Torvalds , Andrea Arcangeli , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , linux-s390@vger.kernel.org Subject: Re: [PATCH 19/25] mm/s390: Use mm_fault_accounting() Message-ID: <20200616163510.GD11838@xz-x1> References: <20200615221607.7764-1-peterx@redhat.com> <20200615222302.8452-1-peterx@redhat.com> <20200616155933.GA12897@oc3871087118.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200616155933.GA12897@oc3871087118.ibm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Alexander, On Tue, Jun 16, 2020 at 05:59:33PM +0200, Alexander Gordeev wrote: > > @@ -489,21 +489,7 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access) > > if (unlikely(fault & VM_FAULT_ERROR)) > > goto out_up; > > > > - /* > > - * Major/minor page fault accounting is only done on the > > - * initial attempt. If we go through a retry, it is extremely > > - * likely that the page will be found in page cache at that point. > > - */ > > if (flags & FAULT_FLAG_ALLOW_RETRY) { > > - if (fault & VM_FAULT_MAJOR) { > > - tsk->maj_flt++; > > - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, > > - regs, address); > > - } else { > > - tsk->min_flt++; > > - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, > > - regs, address); > > - } > > if (fault & VM_FAULT_RETRY) { > > if (IS_ENABLED(CONFIG_PGSTE) && gmap && > > (flags & FAULT_FLAG_RETRY_NOWAIT)) { > > Seems like the call to mm_fault_accounting() will be missed if > we entered here with FAULT_FLAG_RETRY_NOWAIT flag set, since it > jumps to "out_up"... This is true as a functional change. However that also means that we've got a VM_FAULT_RETRY, which hints that this fault has been requested to retry rather than handled correctly (for instance, due to some try_lock failed during the fault process). To me, that case should not be counted as a page fault at all? Or we might get the same duplicated accounting when the page fault retried from a higher stack. Thanks, -- Peter Xu