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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham 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 17805C43382 for ; Tue, 25 Sep 2018 16:49:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CFF5E2086E for ; Tue, 25 Sep 2018 16:49:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CFF5E2086E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727434AbeIYW5b (ORCPT ); Tue, 25 Sep 2018 18:57:31 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:61683 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726664AbeIYW5a (ORCPT ); Tue, 25 Sep 2018 18:57:30 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 42KRqT1SRSz9ttCY; Tue, 25 Sep 2018 18:49:09 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id jHxxCneQgvEF; Tue, 25 Sep 2018 18:49:09 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 42KRqT0qnnz9ttCN; Tue, 25 Sep 2018 18:49:09 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 195DF8B7E5; Tue, 25 Sep 2018 18:49:09 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 1wtcYGRQcqLe; Tue, 25 Sep 2018 18:49:09 +0200 (CEST) Received: from PO15451 (unknown [192.168.232.3]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 78E868B7C8; Tue, 25 Sep 2018 18:49:08 +0200 (CEST) Subject: Re: [PATCH v4 15/20] powerpc/mm: Avoid useless lock with single page fragments To: "Aneesh Kumar K.V" , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , aneesh.kumar@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <7efec0c76fa692513c806871151a7ae20e99fe05.1537288312.git.christophe.leroy@c-s.fr> <78cb82d6-1a13-150d-9daa-021bd2f98e7a@linux.ibm.com> From: Christophe LEROY Message-ID: <0c09b968-b3ef-ca89-9bd4-bf9df353ff50@c-s.fr> Date: Tue, 25 Sep 2018 18:49:07 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <78cb82d6-1a13-150d-9daa-021bd2f98e7a@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 19/09/2018 à 04:56, Aneesh Kumar K.V a écrit : > On 9/18/18 10:27 PM, Christophe Leroy wrote: >> There is no point in taking the page table lock as >> pte_frag is always NULL when we have only one fragment. >> >> Signed-off-by: Christophe Leroy >> --- >>   arch/powerpc/mm/pgtable-frag.c | 3 +++ >>   1 file changed, 3 insertions(+) >> >> diff --git a/arch/powerpc/mm/pgtable-frag.c >> b/arch/powerpc/mm/pgtable-frag.c >> index bc924822dcd6..ab4910e92aaf 100644 >> --- a/arch/powerpc/mm/pgtable-frag.c >> +++ b/arch/powerpc/mm/pgtable-frag.c >> @@ -85,6 +85,9 @@ static pte_t *get_pte_from_cache(struct mm_struct *mm) >>   { >>       void *pte_frag, *ret; >> >> +    if (PTE_FRAG_NR == 1) >> +        return NULL; >> + >>       spin_lock(&mm->page_table_lock); >>       ret = mm->context.pte_frag; >>       if (ret) { >> > > May be update get_pmd_from_cache too? > Ok, done in v5 Christophe