linux-kernel - Re: [RFC][PATCH] create workqueue threads only when needed

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Message-ID: <20090131101502.7ce8e7af@infradead.org>
Date:	Sat, 31 Jan 2009 10:15:02 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC][PATCH] create workqueue threads only when needed

On Sat, 31 Jan 2009 19:03:49 +0100
Frederic Weisbecker <fweisbec@...il.com> wrote:

> > one thing to look at for work queues that never get work is to see
> > if they are appropriate for the async function call interface
> > (the only requirement for that is that they need to cope with
> > calling inline in exceptional cases)
> > 
> 
> 
> Hi Arjan,
> 
> There is one thing that make it hard to replace workqueues in such
> cases, there is not guarantee the function will run in user context
> because of this condition:
> 
> if (!async_enabled || !entry || atomic_read(&entry_count) > MAX_WORK)
> 
> I wanted to replace kpsmoused with an async function but I want to
> schedule a slow work that can't be done from irq...

if there is enough value in having a variant that is guaranteed to
always run from a thread we could add that. Likely that needs that the 
caller passes in a bit of memory, but that's not too big a deal.
If there is only 1 in the entire kernel it might not be worth it,
but if it's a common pattern then for sure...

do you have a feeling on how common this is ?



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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