From: Ted Ts'o Subject: Re: [PATCH] jbd2: Use atomic variables to avoid taking t_handle_lock in jbd2_journal_stop Date: Mon, 2 Aug 2010 20:06:09 -0400 Message-ID: <20100803000609.GI25653@thunk.org> References: <1280753306-23871-1-git-send-email-tytso@mit.edu> <1280790152.3966.14.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ext4 Developers List , Keith Maanthey , Eric Whitney To: john stultz Return-path: Received: from THUNK.ORG ([69.25.196.29]:53838 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751358Ab0HCAGN (ORCPT ); Mon, 2 Aug 2010 20:06:13 -0400 Content-Disposition: inline In-Reply-To: <1280790152.3966.14.camel@localhost.localdomain> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Aug 02, 2010 at 04:02:32PM -0700, john stultz wrote: > >From these numbers, it looks like the atomic variables are a minor > improvement for -rt, but the improvement isn't as drastic as the earlier > j_state lock change, or the vfs scalability patchset. Thanks for doing this quick test run! I was expecting to see a more dramatic difference, since the j_state_lock patch removed one of the two global locks in jbd2_journal_stop, and the t_handle_lock patch removed the second of the two global locks. But I guess the j_state_lock contention in start_this_handle() is still the dominating factor. It's interesting that apparently the latest t_handle_lock patch doesn't seem to make much difference unless the VFS scalability patch is also applied. I'm not sure why that makes a difference, but it's nice to know that with the VFS scalability patch it does seem to help, even if it doesn't help as much as I had hoped. OK, I guess we'll have to start working on the more aggressive scalability fix ups.... - Ted