From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Kent Subject: Re: [PATCH 0/6] autofs4: support RCU-walk Date: Fri, 11 Jul 2014 10:49:52 +0800 Message-ID: <1405046992.2574.10.camel@perseus.fritz.box> References: <20140709233541.4525.25151.stgit@notabene.brown> <1404978220.2609.25.camel@perseus.fritz.box> <20140710182519.79120b90@notabene.brown> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=themaw.net; h= message-id:subject:from:to:cc:date:in-reply-to:references :content-type:mime-version:content-transfer-encoding; s=mesmtp; bh=7JQ1M99wrjAibcFrOE3xvdlcwyw=; b=iINWTN+P8DCPpNNii7CKat6rCrgW nzBEQEqymlqlc5+NrnMD8JxO6V0Sn5MqnbKhLOjl6h+2BpXuI822dEWIeaKfT96X oTQernBjpd6mjYEh0k7w1VxOgQS7N6ZFIktV65WbOSeuWjI2cys9IdlRCopY1HNY vvq6yuHlLBxdtiw= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=message-id:subject:from:to:cc:date :in-reply-to:references:content-type:mime-version :content-transfer-encoding; s=smtpout; bh=7JQ1M99wrjAibcFrOE3xvd lcwyw=; b=RpGetqD/Aij/iYPK5bDbuvxOCHYA1C5G8Z557wMLLt60aHulqYlGu0 hqgyd3VgMjpbVLwGP/LTSA+XpOBzXO+MsK+ZwTzhkXvl3VTIW4y7qLukpx5nSzcI TuAarNvcmAYI/SfP7rPl2k5+VbiCC8K0EKsYErnSoGMnf7e8/POZQ= In-Reply-To: <20140710182519.79120b90@notabene.brown> Sender: autofs-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: NeilBrown Cc: autofs@vger.kernel.org, linux-kernel@vger.kernel.org On Thu, 2014-07-10 at 18:25 +1000, NeilBrown wrote: > On Thu, 10 Jul 2014 15:43:40 +0800 Ian Kent wrote: > > > 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? > > Exactly right - that thirds last patch was "obviously straight forward", so > is naturally the one that I have already found a bug in (the patch assumes > that autofs4_check_leaves returns a different dentry, which clearly isn't > true). Ha, IIRC that was to support the old pseudo direct mounts that would expire the leaves of a tree independently. That was a long time ago now and probably isn't used but it should remain think. I'll need to have a look at that too, to refresh my memory. > > I'll repost it, probably on Monday. > > > > > Thanks for your effort Bruce, > > Ian > > > > http://www.youtube.com/watch?v=_f_p0CgPeyA > > (Usually when people get my name wrong they call me "Ian", so you calling me > Bruce is both slightly ironic and quite refreshing!) LOL, but I have a lame excuse! I was thinking Bruce Fields when replying since have the impression you both work in similar areas. Ian