linux-kernel - Re: [PATCH 05/10] block: remove per-queue plugging

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Message-ID: <4D761FE1.20503@fusionio.com>
Date:	Tue, 8 Mar 2011 13:24:01 +0100
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hch@...radead.org" <hch@...radead.org>, NeilBrown <neilb@...e.de>
Subject: Re: [PATCH 05/10] block: remove per-queue plugging

On 2011-03-04 05:00, Vivek Goyal wrote:
> On Sat, Jan 22, 2011 at 01:17:24AM +0000, Jens Axboe wrote:
> 
> [..]
>>  mm/page-writeback.c                |    2 +-
>>  mm/readahead.c                     |   12 ---
>>  mm/shmem.c                         |    1 -
>>  mm/swap_state.c                    |    5 +-
>>  mm/swapfile.c                      |   37 --------
>>  mm/vmscan.c                        |    2 +-
>>  118 files changed, 153 insertions(+), 1248 deletions(-)
> 
> block/blk-throttle.c also uses blk_unplug(). We need to get rid of that
> also.

Done.

> [..]
>> @@ -632,8 +630,6 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
>>  		 * don't force unplug of the queue for that case.
>>  		 * Clear unplug_it and fall through.
>>  		 */
> 
> Above comments now seem to be redundant.

Killed.

>> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
>> index b9e1e15..5ef136c 100644
>> --- a/drivers/md/dm-raid.c
>> +++ b/drivers/md/dm-raid.c
>> @@ -394,7 +394,7 @@ static void raid_unplug(struct dm_target_callbacks *cb)
>>  {
>>  	struct raid_set *rs = container_of(cb, struct raid_set, callbacks);
>>  
>> -	md_raid5_unplug_device(rs->md.private);
>> +	md_raid5_kick_device(rs->md.private);
> 
> With all the unplug logic gone, I think we can get rid of blk_sync_queue()
> call from md. It looks like md was syncing the queue just to make sure
> that unplug_fn is not called again. Now all that logic is gone so it
> should be redundant.
> 
> Also we can probably get rid of some queue_lock taking instances in
> md code. NeilBrown recently put following patch in, which is taking
> queue lock only around plug functions. Now queue plugging gone,
> I guess it should not be required.

Agree on both accounts. I'll leave that out for this version, though.

-- 
Jens Axboe

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