redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

block: Reserve only one queue tag for sync IO if only 3 tags are available 

In case a device has three tags available we still reserve two of them
for sync IO. That leaves only a single tag for async IO such as
writeback from flusher thread which results in poor performance.

Allow async IO to consume two tags in case queue has three tag availabe
to get a decent async write performance.

This patch improves streaming write performance on a machine with such disk
from ~21 MB/s to ~52 MB/s. Also postmark throughput in presence of
streaming writer improves from 8 to 12 transactions per second so sync
IO doesn't seem to be harmed in presence of heavy async writer.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
hifive-unleashed-5.1
Jan Kara 2013-06-28 21:32:27 +02:00 committed by Jens Axboe
parent a5faeaf910
commit a6b3f7614c
1 changed files with 9 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
block/blk-tag.c
View File

@ -348,9 +348,16 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
*/
max_depth = bqt->max_depth;
if (!rq_is_sync(rq) && max_depth > 1) {
max_depth -= 2;
if (!max_depth)
switch (max_depth) {
case 2:
max_depth = 1;
break;
case 3:
max_depth = 2;
break;
default:
max_depth -= 2;
}
if (q->in_flight[BLK_RW_ASYNC] > max_depth)
return 1;
}