From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751996AbaGJHnr (ORCPT ); Thu, 10 Jul 2014 03:43:47 -0400 Received: from out2-smtp.messagingengine.com ([66.111.4.26]:38737 "EHLO out2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751760AbaGJHno (ORCPT ); Thu, 10 Jul 2014 03:43:44 -0400 X-Sasl-enc: 5A2kI+z/bXkT3xsz3WaxjeJQyRqEaZKf65QAEu6lubHl 1404978223 Message-ID: <1404978220.2609.25.camel@perseus.fritz.box> Subject: Re: [PATCH 0/6] autofs4: support RCU-walk From: Ian Kent To: NeilBrown Cc: autofs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 10 Jul 2014 15:43:40 +0800 In-Reply-To: <20140709233541.4525.25151.stgit@notabene.brown> References: <20140709233541.4525.25151.stgit@notabene.brown> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4 (3.10.4-2.fc20) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2014-07-10 at 09:41 +1000, NeilBrown wrote: > autofs4 currently doesn't support RCU-walk - it immediately > aborts any attempt at RCU-walk to force REF-walk for path name > lookup. > > This can cause a significant performance impact on multi-core > systems. > I have a client with a test case which spends >80% of its time > waiting for spinlocks with a "make -j 40" on a 40 core system. Right, sounds worth the effort. > > This patchset aims to remove most of these spinlocks. To be fully > effective in the particular case it needs a second patch set which > makes NFS RCU-walk friendly, but one thing at a time. > > This has only been lightly tested so far so I'm really after feed-back > rather than to have the patch set accepted, though the first two > patches are trivial and could be taken immediately. I've only scanned the patches so far, I'll need to spend a bit more time on them before I can comment. I'm going to be pressed for time for at least several days so I won't be able to get to this right away. I expect the submount_test I use to stress path walking and expire to mount transitions will likely be a good test to use. I haven't used it in my personal environment for quite a while now so I'll need to have a look around and see if I can still find a suitable set of scripts. Otherwise I'll need to decouple it from the RedHat automated test environment. > > The last two patches are the most interesting so review comments on > those are particularly welcome. Again I haven't looked closely at these but don't you mean the last three patches or am I just fussing over an obviously straight forward patch 3? Thanks for your effort Bruce, Ian