Lukas Czerner <lczerner@xxxxxxxxxx> writes: > On Thu, 28 Apr 2011, Lukas Czerner wrote: > >> On Wed, 27 Apr 2011, Jeff Moyer wrote: >> >> > Lukas Czerner <lczerner@xxxxxxxxxx> writes: >> > >> > > Currently we are waiting for every submitted REQ_DISCARD bio separately, >> > > but it can have unwanted consequences of repeatedly flushing the queue, >> > > so we rather submit bios in batches and wait for the entire batch, hence >> > > narrowing the window of other ios going in. >> > > >> > > Use bio_batch_end_io() and struct bio_batch for that purpose, the same >> > > is used by blkdev_issue_zeroout(). Also change bio_batch_end_io() so we >> > > always set !BIO_UPTODATE in the case of error and remove the check for >> > > bb, since we are the only user of this function and we always set this. >> > > >> > > Remove bio_get()/bio_put() from the blkdev_issue_discard() since >> > > bio_alloc() and bio_batch_end_io() is doing the same thing, hence it is >> > > not needed anymore. >> > > >> > > I have done simple dd testing with surprising results. The script I have >> > > used is: >> > > >> > > for i in $(seq 10); do >> > > echo $i >> > > dd if=/dev/sdb1 of=/dev/sdc1 bs=4k & >> > > sleep 5 >> > > done >> > > /usr/bin/time -f %e ./blkdiscard /dev/sdc1 >> > > >> > > Running time of BLKDISCARD on the whole device: >> > > with patch without patch >> > > 0.95 15.58 >> > > >> > > So we can see that in this artificial test the kernel with the patch >> > > applied is approx 16x faster in discarding the device. >> > >> > I don't see any major problems here. I would like you to test >> > explicitly for queue_flag_discard before submitting any bios, though. > > Btw, this is already in there: > > if (!blk_queue_discard(q)) > return -EOPNOTSUPP; > > at the top of the function. Boy, how did I miss that? ;-) Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
