From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Tue, 01 Apr 2008 22:43:40 -0700 (PDT) Received: from larry.melbourne.sgi.com (larry.melbourne.sgi.com [134.14.52.130]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with SMTP id m325hToY032646 for ; Tue, 1 Apr 2008 22:43:32 -0700 Date: Wed, 2 Apr 2008 15:44:03 +1000 From: David Chinner Subject: Re: [Patch] Cacheline align xlog_t Message-ID: <20080402054403.GF103491721@sgi.com> References: <20080401231552.GV103491721@sgi.com> <47F3293C.6090708@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47F3293C.6090708@sgi.com> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Lachlan McIlroy Cc: David Chinner , xfs-dev , xfs-oss On Wed, Apr 02, 2008 at 04:35:40PM +1000, Lachlan McIlroy wrote: > >*/ > >- uint l_sectbb_log; /* log2 of sector size in > >BBs */ > >- uint l_sectbb_mask; /* sector size (in BBs) > >- * alignment mask */ > >-} xlog_t; > >+ > >+ /* The following field are used for debugging; need to hold > >icloglock */ > >+#ifdef DEBUG > >+ char *l_iclog_bak[XLOG_MAX_ICLOGS]; > >+#endif > >+ > >+} xlog_t ____cacheline_aligned_in_smp; > Is it necessary to add a ____cacheline_aligned_in_smp tag here? The > important sections of the xlog_t structure are already tagged. This just means that the start of the structure is cacheline aligned. I don't think the internal alignment commands force the entire structure to be cacheline aligned, merely pad the struture internally. In that case, even though the specific internal parts of the structure are on separate cache lines, there's no guarantee that all the related members are on the same cacheline. Hence I'm explicitly stating the exact alignment I want for the structure.... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group