linux-kernel - Re: [PATCH] virtio_balloon: Convert "vballon" kthread into a workqueue

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Message-ID: <20140928124318.GA3736@mtj.dyndns.org>
Date:	Sun, 28 Sep 2014 08:43:18 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Petr Mladek <pmladek@...e.cz>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_balloon: Convert "vballon" kthread into a
 workqueue

On Thu, Sep 25, 2014 at 06:20:41PM +0200, Petr Mladek wrote:
...
>     1st create_freezable_workqueue("vballoon_wq");

All create_*workqueue() interfaces are deprecated.  Please don't
create new usages.  They map to alloc_*workqueue() anyway.

>     2nd alloc_workqueue("vballoon_wq", WQ_FREEZABLE | WQ_MEM_RECLAIM, 0);

Is WQ_MEM_RECLAIM necessary here?  Does virtio_balloon depended upon
from memory allocation path?

...
> The 2nd way to create the workqueue has about the same results as kthread.
> This is why it is used in the patch.

You're testing WQ_UNBOUND vs. !WQ_UNBOUND and yes for most use cases,
!WQ_UNBOUND will be more efficient.  The right thing to do in most
cases is using alloc_workqueue() w/ as minimum extra flags as
possible.

Thanks!

-- 
tejun
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