From: Liu Bo <bo.li.liu@oracle.com>
To: john terragon <jterragon@gmail.com>
Cc: Chris Murphy <lists@colorremedies.com>,
Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: kernel 3.17-rc3: task rsync:2524 blocked for more than 120 seconds
Date: Wed, 3 Sep 2014 17:14:45 +0800 [thread overview]
Message-ID: <20140903091444.GC3814@localhost.localdomain> (raw)
In-Reply-To: <CANg_oxxdeY-oMrs4xdamTejLwkGMkyJJsZw6D_UyfvkD0u+Tfg@mail.gmail.com>
On Wed, Sep 03, 2014 at 08:03:51AM +0200, john terragon wrote:
> I tried the same routine on 32GB usb sticks. Same exact problems. 32GB
> seems a bit much for a --mixed btrfs.
> I haven't tried ssd_spread, maybe it's beneficial. However, as I wrote
> above, disabling autodefrag gets rid completely of the "INFO: hung
> task" messages but even though the kernel doesn't complain about
> blocked kworkers, the rsync process still blocks for several minutes
> throughout the whole copy.
It's very nice to know that you can reproduce it with autodefrag.
I made a few analysis on the provided blocked stacks, the key is what blocks
writing free space cache's pages to finish, it sits on wait_on_page_bit() which
expects a WRITEBACK bit.
Could you please paste the output of sysrq-w and sysrq-t when you get that hang?
thanks,
-liubo
>
>
> On Wed, Sep 3, 2014 at 4:44 AM, Chris Murphy <lists@colorremedies.com> wrote:
> >
> > On Sep 2, 2014, at 12:40 AM, Duncan <1i5t5.duncan@cox.net> wrote:
> >>
> >> Mkfs.btrfs used to default to 4 KiB node/leaf sizes; now days it defaults
> >> to 16 KiB as that's far better for most usage. I wonder if USB sticks
> >> are an exception...
> >
> > USB sticks > 1 GB get 16KB nodesize also. At <= 1 GB, mixed-bg is default as is 4KB nodesize. Probably because queue/rotational is 1 for USB sticks, they mount without ssd or ssd_spread which may be unfortunate (I haven't benchmarked it but I suspect ssd_spread would work well for USB sticks).
> >
> > It was suggested a while ago that maybe mixed-bg should apply to larger volumes, maybe up to 8GB or 16GB?
> >
> >
> > Chris Murphy
> >
> > --
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next prev parent reply other threads:[~2014-09-03 9:15 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-01 13:33 kernel 3.17-rc3: task rsync:2524 blocked for more than 120 seconds john terragon
2014-09-01 16:02 ` Chris Mason
2014-09-01 16:36 ` john terragon
2014-09-02 5:20 ` Duncan
2014-09-02 6:12 ` john terragon
2014-09-02 6:40 ` Duncan
2014-09-02 19:56 ` john terragon
2014-09-02 20:10 ` Chris Mason
2014-09-02 20:23 ` john terragon
2014-09-02 20:48 ` john terragon
2014-09-03 1:31 ` john terragon
2014-09-03 12:36 ` Chris Mason
2014-09-03 14:11 ` john terragon
2014-09-03 15:02 ` Chris Murphy
2014-09-03 2:44 ` Chris Murphy
2014-09-03 5:37 ` Duncan
2014-09-03 6:03 ` john terragon
2014-09-03 9:14 ` Liu Bo [this message]
2014-09-03 3:32 ` Zygo Blaxell
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