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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 F3734C49ED6 for ; Wed, 11 Sep 2019 19:57:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC205206A5 for ; Wed, 11 Sep 2019 19:57:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="YuuZ1SR9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730442AbfIKT5v (ORCPT ); Wed, 11 Sep 2019 15:57:51 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:54668 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728244AbfIKT5u (ORCPT ); Wed, 11 Sep 2019 15:57:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=9jE3mtkHHko+7r8PMAvmKkCu21SGOTAKiQ2sFX5q1e8=; b=YuuZ1SR9/A3UTMvsgjSd5CDmd Bht4qf7T7gzPP6ceP3qR0rUCabFLX3Ofmr1X48wwNvc7OioQfaRQY15yoV7wM8Md+Lttifi18jP4N 2zoqeakteIneE6RomJ18Svhc3HMcSNpA9808NWbTJed7wGaWgOW4NIpEuLgedepcI9h5LOFReSKD8 3JDMy6OdPsmFtRfTBIR+HfAyJMgJ+Jnj8cBaaEyynEzWbevqJ6Z1x/AzF0dzQP9Uw1L3uZzKSJVM/ TwSAA+eEApViP9KU8PZo0eQ0O/NEK3imDNt2fcN+0/CxKA18HaTn+i8NqOpUxE/Zb8FY+MwvYdPuH GiGSo8+Vg==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.2 #3 (Red Hat Linux)) id 1i88kL-0007F3-I8; Wed, 11 Sep 2019 19:57:45 +0000 Date: Wed, 11 Sep 2019 12:57:45 -0700 From: Matthew Wilcox To: Waiman Long 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 Subject: Re: [PATCH 5/5] hugetlbfs: Limit wait time when trying to share huge PMD Message-ID: <20190911195745.GI29434@bombadil.infradead.org> References: <20190911150537.19527-1-longman@redhat.com> <20190911150537.19527-6-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190911150537.19527-6-longman@redhat.com> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > +static inline bool i_mmap_timedlock_write(struct address_space *mapping, > + ktime_t timeout) > +{ > + return down_write_timedlock(&mapping->i_mmap_rwsem, timeout); > +}