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From: Eric Sandeen <sandeen@sandeen.net>
To: Tejun Heo <tj@kernel.org>
Cc: Eric Sandeen <sandeen@redhat.com>, xfs-oss <xfs@oss.sgi.com>
Subject: Re: [PATCH 2/2] xfs: mark the xfs-alloc workqueue as high priority
Date: Sat, 10 Jan 2015 18:04:30 -0600	[thread overview]
Message-ID: <54B1BE0E.7020302@sandeen.net> (raw)
In-Reply-To: <20150110192852.GD25319@htj.dyndns.org>

On 1/10/15 1:28 PM, Tejun Heo wrote:
> Hello, Eric.


> As long as the split worker is queued on a separate workqueue, it's
> not really stuck behind xfs_end_io's.  If the global pool that the
> work item is queued on can't make forward progress due to memory
> pressure, the rescuer will be summoned and it will pick out that work
> item and execute it.

Ok, but that's not happening...

> The only reasons that work item would stay there are
> 
> * The rescuer is already executing something else from that workqueue
>   and that one is stuck.

I'll have to look at that.  I hope I still have access to the core...

> * The worker pool is still considered to be making forward progress -
>   there's a worker which isn't blocked and can burn CPU cycles.

AFAICT, the first thing in the pool is the xffs_end_io blocked waiting for the ilock.

I assume it's only the first one that matters?

>   ie. if you have a busy spinning work item on the per-cpu workqueue,
>   it can stall progress.

...

> Again, if xfs is using workqueue correctly, that work item shouldn't
> get stuck at all.  What other workqueues are doing is irrelevant.

and yet here we are; one of us must be missing something.  It's quite
possibly me :) but we definitely have this thing wedged, and moving
the xfsalloc item to the front via high priority did solve it.  Not saying
it's the right solution, just a data point.

Thanks,
-Eric
 
> Thanks.
> 

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  reply	other threads:[~2015-01-11  0:04 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-09 18:08 [PATCH 0/2] xfs: make xfs allocation workqueue per-mount, and high priority Eric Sandeen
2015-01-09 18:10 ` [PATCH 1/2] xfs: make global xfsalloc workqueue per-mount Eric Sandeen
2015-01-12 15:35   ` Brian Foster
2015-01-09 18:12 ` [PATCH 2/2] xfs: mark the xfs-alloc workqueue as high priority Eric Sandeen
2015-01-09 18:23   ` Tejun Heo
2015-01-09 20:36     ` Eric Sandeen
2015-01-10 19:28       ` Tejun Heo
2015-01-11  0:04         ` Eric Sandeen [this message]
2015-01-11  6:33           ` Tejun Heo
2015-01-12 20:09         ` Eric Sandeen
2015-01-12 22:53           ` Tejun Heo
2015-01-12 23:12             ` Eric Sandeen
2015-01-12 23:37               ` Tejun Heo
2015-01-13 19:08                 ` Eric Sandeen
2015-01-13 20:19                   ` Tejun Heo
2015-01-13 20:29                     ` Eric Sandeen
2015-01-13 20:46                       ` Tejun Heo
2015-01-13 22:58                         ` Eric Sandeen
2015-01-13 23:35                           ` [PATCH wq/for-3.19] workqueue: fix subtle pool management issue which can stall whole worker_pool Tejun Heo
2015-01-16 19:32                             ` [PATCH workqueue wq/for-3.19-fixes] " Tejun Heo
2015-01-19  2:15                               ` Lai Jiangshan
2015-01-09 23:28     ` [PATCH 2/2] xfs: mark the xfs-alloc workqueue as high priority Dave Chinner
2015-01-10 17:41       ` Tejun Heo
2015-01-12  3:30         ` Dave Chinner
2015-01-13 20:50           ` Tejun Heo

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