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authorNathan Huckleberry <nhuck@google.com>2022-08-30 21:44:44 +0300
committerMike Snitzer <snitzer@kernel.org>2022-10-19 00:17:47 +0300
commitafd41fff9c73ccc3757e94ad727d2a9ac4d7f6cb (patch)
tree236db1c94c01fb1a99a1006205121f5a1f5a3c00 /drivers/md
parentcea446630feab57f49d47abccf206e9725019cce (diff)
downloadlinux-afd41fff9c73ccc3757e94ad727d2a9ac4d7f6cb.tar.xz
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.c18
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";