Return-Path: X-Original-To: apmail-hbase-issues-archive@www.apache.org Delivered-To: apmail-hbase-issues-archive@www.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id 7E79410F6C for ; Fri, 6 Mar 2015 23:17:48 +0000 (UTC) Received: (qmail 34566 invoked by uid 500); 6 Mar 2015 23:17:39 -0000 Delivered-To: apmail-hbase-issues-archive@hbase.apache.org Received: (qmail 34518 invoked by uid 500); 6 Mar 2015 23:17:39 -0000 Mailing-List: contact issues-help@hbase.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Delivered-To: mailing list issues@hbase.apache.org Received: (qmail 34506 invoked by uid 99); 6 Mar 2015 23:17:39 -0000 Received: from arcas.apache.org (HELO arcas.apache.org) (140.211.11.28) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 06 Mar 2015 23:17:39 +0000 Date: Fri, 6 Mar 2015 23:17:39 +0000 (UTC) From: "Lars Hofhansl (JIRA)" To: issues@hbase.apache.org Message-ID: In-Reply-To: References: Subject: [jira] [Commented] (HBASE-13082) Coarsen StoreScanner locks to RegionScanner 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/HBASE-13082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14351103#comment-14351103 ] Lars Hofhansl commented on HBASE-13082: --------------------------------------- I'll revert until I can work out what the issue is. Sorry about this. > Coarsen StoreScanner locks to RegionScanner > ------------------------------------------- > > Key: HBASE-13082 > URL: https://issues.apache.org/jira/browse/HBASE-13082 > Project: HBase > Issue Type: Bug > Reporter: Lars Hofhansl > Assignee: Lars Hofhansl > Fix For: 2.0.0, 1.1.0 > > Attachments: 13082-test.txt, 13082.txt, 13082.txt, gc.png, gc.png, gc.png, hits.png, next.png, next.png > > > Continuing where HBASE-10015 left of. > We can avoid locking (and memory fencing) inside StoreScanner by deferring to the lock already held by the RegionScanner. > In tests this shows quite a scan improvement and reduced CPU (the fences make the cores wait for memory fetches). > There are some drawbacks too: > * All calls to RegionScanner need to be remain synchronized > * Implementors of coprocessors need to be diligent in following the locking contract. For example Phoenix does not lock RegionScanner.nextRaw() and required in the documentation (not picking on Phoenix, this one is my fault as I told them it's OK) > * possible starving of flushes and compaction with heavy read load. RegionScanner operations would keep getting the locks and the flushes/compactions would not be able finalize the set of files. > I'll have a patch soon. -- This message was sent by Atlassian JIRA (v6.3.4#6332)