diff options
author | Nathan Huckleberry <nhuck@google.com> | 2022-08-30 18:44:44 +0000 |
---|---|---|
committer | Mike Snitzer <snitzer@kernel.org> | 2022-10-18 17:17:47 -0400 |
commit | afd41fff9c73ccc3757e94ad727d2a9ac4d7f6cb (patch) | |
tree | 236db1c94c01fb1a99a1006205121f5a1f5a3c00 /drivers/md | |
parent | cea446630feab57f49d47abccf206e9725019cce (diff) | |
download | linux-afd41fff9c73ccc3757e94ad727d2a9ac4d7f6cb.tar.bz2 |
dm verity: enable WQ_HIGHPRI on verify_wq
WQ_HIGHPRI increases throughput and decreases disk latency when using
dm-verity. This is important in Android for camera startup speed.
The following tests were run by doing 60 seconds of random reads using
a dm-verity device backed by two ramdisks.
Without WQ_HIGHPRI
lat (usec): min=13, max=3947, avg=69.53, stdev=50.55
READ: bw=51.1MiB/s (53.6MB/s), 51.1MiB/s-51.1MiB/s (53.6MB/s-53.6MB/s)
With WQ_HIGHPRI:
lat (usec): min=13, max=7854, avg=31.15, stdev=30.42
READ: bw=116MiB/s (121MB/s), 116MiB/s-116MiB/s (121MB/s-121MB/s)
Further testing was done by measuring how long it takes to open a
camera on an Android device.
Without WQ_HIGHPRI
Total verity work queue wait times (ms):
880.960, 789.517, 898.852
With WQ_HIGHPRI:
Total verity work queue wait times (ms):
528.824, 439.191, 433.300
The average time to open the camera is reduced by 350ms (or 40-50%).
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Diffstat (limited to 'drivers/md')
-rw-r--r-- | drivers/md/dm-verity-target.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index 8a00cc42e498..ccf5b852fbf7 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -1401,14 +1401,16 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) /* WQ_UNBOUND greatly improves performance when running on ramdisk */ wq_flags = WQ_MEM_RECLAIM | WQ_UNBOUND; - if (v->use_tasklet) { - /* - * Allow verify_wq to preempt softirq since verification in - * tasklet will fall-back to using it for error handling - * (or if the bufio cache doesn't have required hashes). - */ - wq_flags |= WQ_HIGHPRI; - } + /* + * Using WQ_HIGHPRI improves throughput and completion latency by + * reducing wait times when reading from a dm-verity device. + * + * Also as required for the "try_verify_in_tasklet" feature: WQ_HIGHPRI + * allows verify_wq to preempt softirq since verification in tasklet + * will fall-back to using it for error handling (or if the bufio cache + * doesn't have required hashes). + */ + wq_flags |= WQ_HIGHPRI; v->verify_wq = alloc_workqueue("kverityd", wq_flags, num_online_cpus()); if (!v->verify_wq) { ti->error = "Cannot allocate workqueue"; |