blk-throttle: Use blk_plug in throttle code (Was: Re: [PATCH 05/10]block: remove per-queue plugging)

From: Vivek Goyal
Date: Tue Mar 08 2011 - 17:10:17 EST


On Tue, Mar 08, 2011 at 01:24:01PM +0100, Jens Axboe wrote:
> 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.

Thanks Jens. Looking at the usage of blk_plug, i think it makes sense to
make use of it in throttle dispatch also. Here is the patch.

blk-throttle: Use blk_plug in throttle dispatch

Use plug in throttle dispatch also as we are dispatching a bunch of
bios in throttle context and some of them might merge.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
block/blk-throttle.c | 3 +++
1 file changed, 3 insertions(+)

Index: linux-2.6-block/block/blk-throttle.c
===================================================================
--- linux-2.6-block.orig/block/blk-throttle.c 2011-03-08 16:43:14.000000000 -0500
+++ linux-2.6-block/block/blk-throttle.c 2011-03-08 16:59:44.359620804 -0500
@@ -770,6 +770,7 @@ static int throtl_dispatch(struct reques
unsigned int nr_disp = 0;
struct bio_list bio_list_on_stack;
struct bio *bio;
+ struct blk_plug plug;

spin_lock_irq(q->queue_lock);

@@ -798,8 +799,10 @@ out:
* immediate dispatch
*/
if (nr_disp) {
+ blk_start_plug(&plug);
while((bio = bio_list_pop(&bio_list_on_stack)))
generic_make_request(bio);
+ blk_finish_plug(&plug);
}
return nr_disp;
}
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