From owner-svn-src-all@freebsd.org Mon Dec 25 21:40:21 2017 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 14C87EA7C71; Mon, 25 Dec 2017 21:40:21 +0000 (UTC) (envelope-from pho@holm.cc) Received: from relay01.pair.com (relay01.pair.com [209.68.5.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E19E4748EA; Mon, 25 Dec 2017 21:40:20 +0000 (UTC) (envelope-from pho@holm.cc) Received: from x2.osted.lan (87-58-223-204-dynamic.dk.customer.tdc.net [87.58.223.204]) by relay01.pair.com (Postfix) with ESMTP id E646DD00386; Mon, 25 Dec 2017 16:40:17 -0500 (EST) Received: from x2.osted.lan (localhost [127.0.0.1]) by x2.osted.lan (8.14.9/8.14.9) with ESMTP id vBPLeFPi013591 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 25 Dec 2017 22:40:15 +0100 (CET) (envelope-from pho@x2.osted.lan) Received: (from pho@localhost) by x2.osted.lan (8.14.9/8.14.9/Submit) id vBPLeFaG013590; Mon, 25 Dec 2017 22:40:15 +0100 (CET) (envelope-from pho) Date: Mon, 25 Dec 2017 22:40:15 +0100 From: Peter Holm To: Mark Johnston Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r327168 - head/sys/vm Message-ID: <20171225214015.GA13298@x2.osted.lan> References: <201712241945.vBOJjGV5051696@repo.freebsd.org> <20171225174946.GA9941@x2.osted.lan> <20171225195117.GA68801@wkstn-mjohnston.west.isilon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171225195117.GA68801@wkstn-mjohnston.west.isilon.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 25 Dec 2017 21:40:21 -0000 On Mon, Dec 25, 2017 at 11:51:17AM -0800, Mark Johnston wrote: > On Mon, Dec 25, 2017 at 06:49:46PM +0100, Peter Holm wrote: > > On Sun, Dec 24, 2017 at 07:45:16PM +0000, Mark Johnston wrote: > > > Author: markj > > > Date: Sun Dec 24 19:45:16 2017 > > > New Revision: 327168 > > > URL: https://svnweb.freebsd.org/changeset/base/327168 > > > > > > Log: > > > Fix two problems with the page daemon control loop. > > > > > > Both issues caused the page daemon to erroneously go to sleep when > > > applications are consuming free pages at a high rate, leaving the > > > application threads blocked in VM_WAIT. > > > > > > 1) After completing an inactive queue scan, concurrent allocations may > > > have prevented the page daemon from meeting the v_free_min threshold. > > > In this case, the page daemon was going to sleep even when the > > > inactive queue contained plenty of clean pages. > > > 2) pagedaemon_wakeup() may be called without the free queues lock held. > > > This can lead to a lost wakeup if a call occurs after the page daemon > > > clears vm_pageout_wanted but before going to sleep. > > > > > > Fix 1) by ensuring that we start a new inactive queue scan immediately > > > if v_free_count < v_free_min after a prior scan. > > > > > > Fix 2) by adding a new subroutine, pagedaemon_wait(), called from > > > vm_wait() and vm_waitpfault(). It wakes up the page daemon if either > > > vm_pages_needed or vm_pageout_wanted is false, and atomically sleeps > > > on v_free_count. > > > > > > Reported by: jeff > > > Reviewed by: alc > > > MFC after: 2 weeks > > > Differential Revision: https://reviews.freebsd.org/D13424 > > > > > > Modified: > > > head/sys/vm/vm_page.c > > > head/sys/vm/vm_pageout.c > > > head/sys/vm/vm_pageout.h > > > > > > > I now see threads blocked in VM_WAIT? > > > > https://people.freebsd.org/~pho/stress/log/mark013.txt > > Hmm, I don't see anything obviously wrong here. v_free_count is 38, well > below the minimum threshold at which threads will block in VM_WAIT. The > page daemon was running and vm_pages_needed is 1, which is expected. > This just looks like a case of the page daemon failing to keep up with > memory pressure. Do you not see threads entering VM_WAIT with this > revision reverted? I have been running the same test on two hosts for one hours without seeing any problems. I'll keep the test run thru the night. -- Peter