From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Sanders Subject: Re: Btrfs switches to using mostly one thread Date: Fri, 09 Dec 2011 12:05:40 +0000 Message-ID: <4EE1F994.4060908@jeremysanders.net> References: <20111208153201.GJ8971@shiny> <4EE0EC68.6040505@jeremysanders.net> <20111208172316.GP8971@shiny> <4EE0F644.6000204@jeremysanders.net> <20111208201112.GU8971@shiny> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed To: Chris Mason , linux-btrfs@vger.kernel.org Return-path: In-Reply-To: <20111208201112.GU8971@shiny> List-ID: On 08/12/11 20:11, Chris Mason wrote: > On Thu, Dec 08, 2011 at 05:39:16PM +0000, Jeremy Sanders wrote: >> On 08/12/11 17:23, Chris Mason wrote: >>> On Thu, Dec 08, 2011 at 04:57:12PM +0000, Jeremy Sanders wrote: >>>> On 08/12/11 15:32, Chris Mason wrote: >>>>> On Thu, Dec 08, 2011 at 03:19:38PM +0000, Jeremy Sanders wrote: >>>>>> Hi - I'm trying out btrfs again, and I see the same old bug in kernel 3.1.4 >>>>>> (Fedora 16, x86_64, dual-core), where after a few hours of writing, it >>>>>> switches from writing with several threads to writing with one: >>>>> >>>>> Ok, I'll try to reproduce this here. Could you please do a sysrq-t, I'd >>>>> like to see what the other delalloc-writers are doing. >>>> >>>> I've attached sysrq-t. It looks like it might be truncated at the >>>> beginning, however. >>> >>> /var/log/messages may have the whole thing, please do check. >> >> That was from /var/log/messages. I think it needs a longer >> log_buf_len. Unfortunately the system hasn't come back from its >> reboot, so it will have to wait until tomorrow when I can get to it >> physically. > > Ok, this trace shows that we have tar sitting in balance_dirty_pages and > we have the single delalloc worker doing requests. The other delalloc > workers don't show up at all. > > So either they are earlier in the trace or they disappeared somehow. > I'll definitely need the full trace if you can send it. I've got the full trace now. It's pretty big (430KB), so I've put it on the web. Here's the state before switching to one thread http://www-xray.ast.cam.ac.uk/~jss/data/btrfs-before.txt Here it is after it has switched to one thread: http://www-xray.ast.cam.ac.uk/~jss/data/btrfs-after.txt Jeremy