Allow user to set the QUEUE_FLAG_NOWAIT optionally using module
parameter to retain the default behaviour. Also, update respective
allocation flags in the write path. Following are the performance
numbers with io_uring fio engine for random read, note that device has
been populated fully with randwrite workload before taking these
numbers :-
* linux-block (for-next) # grep IOPS bc-*fio | column -t
nowait-off-1.fio: read: IOPS=482k, BW=1885MiB/s
nowait-off-2.fio: read: IOPS=484k, BW=1889MiB/s
nowait-off-3.fio: read: IOPS=483k, BW=1886MiB/s
nowait-on-1.fio: read: IOPS=544k, BW=2125MiB/s
nowait-on-2.fio: read: IOPS=547k, BW=2137MiB/s
nowait-on-3.fio: read: IOPS=546k, BW=2132MiB/s
* linux-block (for-next) # grep slat bc-*fio | column -t
nowait-off-1.fio: slat (nsec): min=430, max=5488.5k, avg=2797.52
nowait-off-2.fio: slat (nsec): min=431, max=8252.4k, avg=2805.33
nowait-off-3.fio: slat (nsec): min=431, max=6846.6k, avg=2814.57
nowait-on-1.fio: slat (usec): min=2, max=39086, avg=87.48
nowait-on-2.fio: slat (usec): min=3, max=39519, avg=86.98
nowait-on-3.fio: slat (usec): min=3, max=38880, avg=87.17
* linux-block (for-next) # grep cpu bc-*fio | column -t
nowait-off-1.fio: cpu : usr=2.77%, sys=6.57%, ctx=22015526
nowait-off-2.fio: cpu : usr=2.75%, sys=6.59%, ctx=22003700
nowait-off-3.fio: cpu : usr=2.81%, sys=6.57%, ctx=21938309
nowait-on-1.fio: cpu : usr=1.08%, sys=78.39%, ctx=2744092
nowait-on-2.fio: cpu : usr=1.10%, sys=79.76%, ctx=2537466
nowait-on-3.fio: cpu : usr=1.10%, sys=79.88%, ctx=2528092
Signed-off-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
---
drivers/md/bcache/request.c | 3 ++-
drivers/md/bcache/super.c | 6 ++++++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 67a2e29e0b40..2055a23eb4b7 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -716,9 +716,10 @@ static inline struct search *search_alloc(struct bio *bio,
struct bcache_device *d, struct block_device *orig_bdev,
unsigned long start_time)
{
+ gfp_t gfp = bio->bi_opf & REQ_NOWAIT ? GFP_NOWAIT : GFP_NOIO;
struct search *s;
- s = mempool_alloc(&d->c->search, GFP_NOIO);
+ s = mempool_alloc(&d->c->search, gfp);
closure_init(&s->cl, NULL);
do_bio_hook(s, bio, request_endio);
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 7e9d19fd21dd..f76822bece26 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -28,6 +28,7 @@
unsigned int bch_cutoff_writeback;
unsigned int bch_cutoff_writeback_sync;
+bool bch_nowait;
static const char bcache_magic[] = {
0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca,
@@ -971,6 +972,8 @@ static int bcache_device_init(struct bcache_device *d, unsigned int block_size,
}
blk_queue_flag_set(QUEUE_FLAG_NONROT, d->disk->queue);
+ if (bch_nowait)
+ blk_queue_flag_set(QUEUE_FLAG_NOWAIT, d->disk->queue);
blk_queue_write_cache(q, true, true);
@@ -2933,6 +2936,9 @@ MODULE_PARM_DESC(bch_cutoff_writeback, "threshold to cutoff writeback");
module_param(bch_cutoff_writeback_sync, uint, 0);
MODULE_PARM_DESC(bch_cutoff_writeback_sync, "hard threshold to cutoff writeback");
+module_param(bch_nowait, bool, 0);
+MODULE_PARM_DESC(bch_nowait, "set QUEUE_FLAG_NOWAIT");
+
MODULE_DESCRIPTION("Bcache: a Linux block layer cache");
MODULE_AUTHOR("Kent Overstreet <kent.overstreet@xxxxxxxxx>");
MODULE_LICENSE("GPL");
--
2.40.0
