From: "Miquel van Smoorenburg" <miquels@cistron.net>
To: akpm@osdl.org
Cc: Jens Axboe <axboe@suse.de>, linux-kernel@vger.kernel.org
Subject: Re: 2.6.4-mm2
In-Reply-To: <20040318235200.25c376a9.akpm@osdl.org>
References: <20040314172809.31bd72f7.akpm@osdl.org>
	<200403181737.i2IHbCE09261@mail.osdl.org>
	<20040318100615.7f2943ea.akpm@osdl.org>
	<20040318192707.GV22234@suse.de>
	<20040318191530.34e04cb2.akpm@osdl.org>
	<20040319073919.GY22234@suse.de>
Organization: Cistron Group
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7BIT
Message-Id: <E1B4Gjz-0003BI-00@subspace.cistron-office.nl>
Date: Fri, 19 Mar 2004 10:56:35 +0100
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1796
Lines: 39

In article <20040318235200.25c376a9.akpm@osdl.org> you write:
>Jens Axboe <axboe@suse.de> wrote:
>>  I thought about this last night, and I have a better idea that gets the
>>  same accomplished. The problem right now is indeed that we aren't
>>  tracking who needs to be unplugged, like we used to. The solution is to
>>  do the exact same style plugging (with block helpers) that we used to,
>>  except the plug_list is maintained in the driver. So when you do
>>  dm_unplug(), it doesn't _have_ to iterate the full device list, only
>>  those that do need kicking.
>
>Yes, it would be nice but I fear that it gets complicated.
>
>Is it not the case that two dm maps can refer to the same queue?  Say, one
>map uses /dev/hda1 and another map uses /dev/hda2?
>
>If so, then when the /dev/hda queue is plugged we need to tell both the
>higher-level maps that this queue needs an unplug.  So blk_plug_device()
>and the various unplug functions need to perform upcalls to an arbitrary
>number of higher-level drivers, and those drivers need to keep track of the
>currently-plugged queues without adding data structures to the
>request_queue structure.
>
>It can be done of course, but could get messy.

I implemented exactly this for the congestion stuff. It
isn't perfect, but perhaps it is of some use:
                                                                                
https://www.redhat.com/archives/linux-lvm/2004-February/msg00215.html

It got shot down because it was too complicated..

Mike.
-- 
Netu, v qba'g yvxr gur cynvagrkg :)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/