Re: per-cpu blk_plug_list

From: Andrew Morton <>
Date: 2004-03-03 16:13:09
"Chen, Kenneth W" <> wrote:
> I don't understand the proposal here.  There is a per-device lock
> already.  But the plugged queue need to be on some list outside itself
> so a group of them can be unplugged later on to flush all the I/O.

here's the proposal:

Regarding this:

 And also having looked at Miquel's (currently slightly defective)
 implementation of the any_congested() API for devicemapper:

 I am thinking that an appropriate way of solving the blk_run_queues() lock
 contention problem is to nuke the global plug list altogther and make the
 unplug function a method in struct backing_device_info.

 This is conceptually the appropriate place to put it - it is almost always
 the case that when we run blk_run_queues() it is on behalf of an
 address_space, and the few remaining case can be simply deleted -
 mm/mempool.c is the last one I think.

 The implementation of backing_dev_info.unplug() would have to run the
 unplug_fn of every queue which contributes to the top-level queue (the
 thing which the address_space is sitting on top of).

 We discussed this maybe a year ago with Jens but decided against it for
 complexity reasons, but gee, dm_table_any_congested() isn't complex.  Do we
 forsee any particular problem with this?
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Received on Wed Mar 3 00:17:03 2004

This archive was generated by hypermail 2.1.8 : 2005-08-02 09:20:24 EST