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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 47868C5ACAE for ; Wed, 11 Sep 2019 20:51:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 273342053B for ; Wed, 11 Sep 2019 20:51:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729513AbfIKUvF (ORCPT ); Wed, 11 Sep 2019 16:51:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49166 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729327AbfIKUvE (ORCPT ); Wed, 11 Sep 2019 16:51:04 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6274930821BF; Wed, 11 Sep 2019 20:51:04 +0000 (UTC) Received: from llong.remote.csb (ovpn-121-77.rdu2.redhat.com [10.10.121.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id D11845D6A5; Wed, 11 Sep 2019 20:51:01 +0000 (UTC) Subject: Re: [PATCH 5/5] hugetlbfs: Limit wait time when trying to share huge PMD To: Matthew Wilcox Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Alexander Viro , Mike Kravetz , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Davidlohr Bueso References: <20190911150537.19527-1-longman@redhat.com> <20190911150537.19527-6-longman@redhat.com> <20190911195745.GI29434@bombadil.infradead.org> From: Waiman Long Organization: Red Hat Message-ID: <11361434-ca3d-78ae-e825-8521ee3bfbe6@redhat.com> Date: Wed, 11 Sep 2019 21:51:00 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190911195745.GI29434@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Wed, 11 Sep 2019 20:51:04 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 9/11/19 8:57 PM, Matthew Wilcox wrote: > On Wed, Sep 11, 2019 at 04:05:37PM +0100, Waiman Long wrote: >> To remove the unacceptable delays, we have to limit the amount of wait >> time on the mmap_sem. So the new down_write_timedlock() function is >> used to acquire the write lock on the mmap_sem with a timeout value of >> 10ms which should not cause a perceivable delay. If timeout happens, >> the task will abandon its effort to share the PMD and allocate its own >> copy instead. > If you do a v2, this is *NOT* the mmap_sem. It's the i_mmap_rwsem > which protects a very different data structure from the mmap_sem. > Thanks for reminder. I should have read the code more carefully. Cheers, Longman