On 2012-10-08 19:56, Mike Snitzer wrote: > On Mon, Oct 8, 2012 at 9:11 PM, Shaohua Li <[email protected]> wrote: >> Now discard merge works, add plug for blkdev_issue_discard. This will help >> discard request merge especially for raid0 case. In raid0, a big discard >> request is split to small requests, and if correct plug is added, such small >> requests can be merged in low layer. >> >> Signed-off-by: Shaohua Li <[email protected]> >> --- >> block/blk-lib.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> Index: linux/block/blk-lib.c >> =================================================================== >> --- linux.orig/block/blk-lib.c 2012-09-28 15:09:38.655327319 +0800 >> +++ linux/block/blk-lib.c 2012-10-09 08:45:04.358598888 +0800 >> @@ -48,6 +48,7 @@ int blkdev_issue_discard(struct block_de >> struct bio_batch bb; >> struct bio *bio; >> int ret = 0; >> + struct blk_plug plug; >> >> if (!q) >> return -ENXIO; >> @@ -81,6 +82,7 @@ int blkdev_issue_discard(struct block_de >> bb.flags = 1 << BIO_UPTODATE; >> bb.wait = &wait; >> >> + blk_start_plug(&plug); >> while (nr_sects) { >> unsigned int req_sects; >> sector_t end_sect; >> @@ -117,6 +119,7 @@ int blkdev_issue_discard(struct block_de >> atomic_inc(&bb.done); >> submit_bio(type, bio); >> } >> + blk_finish_plug(&plug); >> >> /* Wait for bios in-flight */ >> if (!atomic_dec_and_test(&bb.done)) > > That plug looks rather coarse-grained. Any adverse affects when mkfs > discards an entire (large) raid0 device? (I suspect not but figured > I'd ask)
Block core auto-unplugs after a certain depth is reached. So it's better to make it coarse than try to second guess when to unplug. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
