linux-kernel - Re: Re: [PATCH 2/2] 2.6.19-rc1-mm1 pktcdvd: bio write congestion

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Message-ID: <Pine.LNX.4.64.0610162128100.633@p4.localdomain>
Date:	Mon, 16 Oct 2006 21:32:37 +0200 (CEST)
From:	Peter Osterlund <petero2@...ia.com>
To:	balagi@...tmail.de
cc:	Jens Axboe <jens.axboe@...cle.com>, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH 2/2] 2.6.19-rc1-mm1 pktcdvd: bio write congestion

On Mon, 16 Oct 2006, balagi@...tmail.de wrote:

> the congestion control will work with both code changes, but i am
> not sure, if using clear_queue_congested() and blk_congestion_wait()
> is the right thing to use here: it works on global level. Any other
> thread/driver/etc. can do a clear_queue_congested() and wake
> up anyone waiting on this global write or read wait queue, resulting to
> unneeded task switches.
> The driver local solution (own waitqueue) would prevent this.....

But it would make the driver more complex. How many extra task switches 
can you get, and how much CPU time does that consume? If it is negligible 
I think it's better to keep the code simple.

-- 
Peter Osterlund - petero2@...ia.com
http://web.telia.com/~u89404340
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