From dev-return-10133-apmail-couchdb-dev-archive=couchdb.apache.org@couchdb.apache.org Tue Jun 08 06:58:36 2010 Return-Path: Delivered-To: apmail-couchdb-dev-archive@www.apache.org Received: (qmail 96528 invoked from network); 8 Jun 2010 06:58:36 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 8 Jun 2010 06:58:36 -0000 Received: (qmail 23479 invoked by uid 500); 8 Jun 2010 06:58:36 -0000 Delivered-To: apmail-couchdb-dev-archive@couchdb.apache.org Received: (qmail 23230 invoked by uid 500); 8 Jun 2010 06:58:36 -0000 Mailing-List: contact dev-help@couchdb.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: dev@couchdb.apache.org Delivered-To: mailing list dev@couchdb.apache.org Received: (qmail 23208 invoked by uid 99); 8 Jun 2010 06:58:35 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 08 Jun 2010 06:58:35 +0000 X-ASF-Spam-Status: No, hits=-1504.9 required=10.0 tests=ALL_TRUSTED,AWL X-Spam-Check-By: apache.org Received: from [140.211.11.22] (HELO thor.apache.org) (140.211.11.22) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 08 Jun 2010 06:58:34 +0000 Received: from thor (localhost [127.0.0.1]) by thor.apache.org (8.13.8+Sun/8.13.8) with ESMTP id o586wElY025291 for ; Tue, 8 Jun 2010 06:58:14 GMT Message-ID: <30758207.20221275980293994.JavaMail.jira@thor> Date: Tue, 8 Jun 2010 02:58:13 -0400 (EDT) From: "Randall Leeds (JIRA)" To: dev@couchdb.apache.org Subject: [jira] Updated: (COUCHDB-767) do a non-blocking file:sync In-Reply-To: <17731849.7081274250652935.JavaMail.jira@thor> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 [ https://issues.apache.org/jira/browse/COUCHDB-767?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Randall Leeds updated COUCHDB-767: ---------------------------------- Attachment: async_fsync.patch Here's my attempt to combine Adam's patch with my patch from COUCHDB-786. In this approach, couch_file exports a sync_file/1 which takes a path instead of a file descriptor. Unlike Adam's patch, the From tag from the handle_call(sync, From, File) that spawns the async sync_file/1 is not passed, but the spawn'd fun replies with the result of sync_file/1. The desirable consequence is that sync_file/1 may be called without going through a gen_server handler. This approach allows the couch_db_updater:commit_data/2 function to call couch_file:sync_file/1 directly, bypassing the gen_server:call operations that COUCHDB-786 was trying to avoid. I think this is win win, but I agree with Adam about testing. I welcome any comprehensive performance suite that could run against these changes to get some detailed statistics. > do a non-blocking file:sync > --------------------------- > > Key: COUCHDB-767 > URL: https://issues.apache.org/jira/browse/COUCHDB-767 > Project: CouchDB > Issue Type: Improvement > Components: Database Core > Affects Versions: 0.11 > Reporter: Adam Kocoloski > Fix For: 1.1 > > Attachments: 767-async-fsync.patch, async_fsync.patch > > > I've been taking a close look at couch_file performance in our production systems. One of things I've noticed is that reads are occasionally blocked for a long time by a slow call to file:sync. I think this is unnecessary. I think we could do something like > handle_call(sync, From, #file{name=Name}=File) -> > spawn_link(fun() -> sync_file(Name, From) end), > {noreply, File}; > and then > sync_file(Name, From) -> > {ok, Fd} = file:open(Name, [read, raw]), > gen_server:reply(From, file:sync(Fd)), > file:close(Fd). > Does anyone see a downside to this? Individual clients of couch_file still see exactly the same behavior as before, only readers are not blocked by syncs initiated in the db_updater process. When data needs to be flushed file:sync is _much_ slower than spawning a local process and opening the file again -- in the neighborhood of 1000x slower even on Linux with its less-than-durable use of vanilla fsync. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.