From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Tue, 01 Apr 2008 18:50:12 -0700 (PDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.168.29]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m321o0oJ026399 for ; Tue, 1 Apr 2008 18:50:02 -0700 Received: from ext.agami.com (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id D07B67268CC for ; Tue, 1 Apr 2008 18:50:33 -0700 (PDT) Received: from ext.agami.com (64.221.212.177.ptr.us.xo.net [64.221.212.177]) by cuda.sgi.com with ESMTP id oowllHUU0NRSfBDv for ; Tue, 01 Apr 2008 18:50:33 -0700 (PDT) Received: from agami.com (mail [192.168.168.5]) by ext.agami.com (8.12.5/8.12.5) with ESMTP id m31L37eL029945 for ; Tue, 1 Apr 2008 14:03:07 -0700 Received: from mx1.agami.com (mx1.agami.com [10.123.10.30]) by agami.com (8.12.11/8.12.11) with ESMTP id m31L37ec015683 for ; Tue, 1 Apr 2008 14:03:07 -0700 Message-ID: <47F2A321.60907@agami.com> Date: Tue, 01 Apr 2008 14:03:29 -0700 From: Michael Nishimoto MIME-Version: 1.0 Subject: Re: Definition of XFS_DQUOT_LOGRES() References: <47F16988.2080406@agami.com> <20080401012856.GL103491721@sgi.com> In-Reply-To: <20080401012856.GL103491721@sgi.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: David Chinner Cc: XFS Mailing List David Chinner wrote: > On Mon, Mar 31, 2008 at 03:45:28PM -0700, Michael Nishimoto wrote: >> The comment for XFS_DQUOT_LOGRES states that we need to reserve space >> for 3 dquots. I can't figure out why we need to add this amount to *all* >> operations and why this amount wasn't added after doing a runtime >> quotaon check. > > It probably could be done that way. But given that: > >> /* >> * In the worst case, when both user and group quotas are on, >> * we can have a max of three dquots changing in a single transaction. >> */ >> #define XFS_DQUOT_LOGRES(mp) (sizeof(xfs_disk_dquot_t) * 3) > > sizeof(xfs_disk_dquot_t) = 104 bytes, > > the overall addition to the reservations is minor considering: > > [0]kdb> xtrres 0xe0000038055ac6c0 > write: 109752 truncate: 223672 rename: 305976 > link: 153144 remove: 153144 symlink: 158520 > create: 158392 mkdir: 158392 ifree: 58936 > ichange: 2104 growdata: 45696 swrite: 384 > addafork: 70584 writeid: 384 attrinval: 179328 > attrset: 22968 attrrm: 90552 clearagi: 1152 > growrtalloc: 66048 growrtzero: 4224 growrtfree: 6272 > [0]kdb> > > on a 14GB filesystem most of the transactions this is added to > are on the far side of 150k and that means we're talking about less > than 0.2% of the entire reservation comes from the dquot. With > larger block sizes and/or larger filesystems, these get much > larger. e.g. same 14GB device, 64k block size instead of 4k: > > [0]kdb> xtrres 0xe00000b8027d39f8 > write: 987576 truncate: 1977272 rename: 2891064 > link: 1445688 remove: 1445688 symlink: 1512504 > create: 1511864 mkdir: 1511864 ifree: 470584 > ichange: 1592 growdata: 395904 swrite: 384 > addafork: 658616 writeid: 384 attrinval: 1581696 > attrset: 329656 attrrm: 791480 clearagi: 640 > growrtalloc: 592640 growrtzero: 65664 growrtfree: 67200 > > The rename reservation is *2.8MB* (up from 300k). IOWs, 300 bytes is > really noise when it comes to reservation space. (OT: See why I want to > increase the log size now? :) > > Is it worth the complexity of adding this dquot reservation at > runtime for a best case reduction of 0.2% in log space reservation > usage? Probably not, but patches can be convincing ;) > > Cheers, > > Dave. Here is a patch to fix a sign problem when growing the log to 2G. --- xfs_log.2.c 2008-04-01 11:55:45.000000000 -0700 +++ xfs_log.3.c 2008-04-01 11:56:53.000000000 -0700 @@ -230,20 +230,24 @@ static void xlog_grant_add_space_write(struct log *log, int bytes) { - log->l_grant_write_bytes += bytes; - if (log->l_grant_write_bytes > log->l_logsize) { - log->l_grant_write_bytes -= log->l_logsize; - log->l_grant_write_cycle++; + int __tmp = (log)->l_logsize - (log)->l_grant_write_bytes; + if (__tmp > bytes) + (log)->l_grant_write_bytes += bytes; + else { + (log)->l_grant_write_cycle++; + (log)->l_grant_write_bytes = bytes - __tmp; } } static void xlog_grant_add_space_reserve(struct log *log, int bytes) { - log->l_grant_reserve_bytes += bytes; - if (log->l_grant_reserve_bytes > log->l_logsize) { - log->l_grant_reserve_bytes -= log->l_logsize; - log->l_grant_reserve_cycle++; + int __tmp = (log)->l_logsize - (log)->l_grant_reserve_bytes; + if (__tmp > bytes) + (log)->l_grant_reserve_bytes += bytes; + else { + (log)->l_grant_reserve_cycle++; + (log)->l_grant_reserve_bytes = bytes - __tmp; } }