diff options
| author | Nathan Huckleberry <nhuck@google.com> | 2023-02-02 04:23:48 +0300 |
|---|---|---|
| committer | Mike Snitzer <snitzer@kernel.org> | 2023-02-02 22:26:09 +0300 |
| commit | c25da5b7baf1d243e6612ba2b97e2a2c4a1376f6 (patch) | |
| tree | 0e6b8982c450d3046619e4c22e26b10b003d0aac /drivers | |
| parent | 5cd6d1d53a1f74222e73d8b42ab7ecf28ee2f34f (diff) | |
| download | linux-c25da5b7baf1d243e6612ba2b97e2a2c4a1376f6.tar.xz | |
dm verity: stop using WQ_UNBOUND for verify_wq
Setting WQ_UNBOUND increases scheduler latency on ARM64. This is
likely due to the asymmetric architecture of ARM64 processors.
I've been unable to reproduce the results that claim WQ_UNBOUND gives
a performance boost on x86-64.
This flag is causing performance issues for multiple subsystems within
Android. Notably, the same slowdown exists for decompression with
EROFS.
| open-prebuilt-camera | WQ_UNBOUND | ~WQ_UNBOUND |
|-----------------------|------------|---------------|
| verity wait time (us) | 11746 | 119 (-98%) |
| erofs wait time (us) | 357805 | 174205 (-51%) |
| sha256 ramdisk random read | WQ_UNBOUND | ~WQ_UNBOUND |
|----------------------------|-----------=---|-------------|
| arm64 (accelerated) | bw=42.4MiB/s | bw=212MiB/s |
| arm64 (generic) | bw=16.5MiB/s | bw=48MiB/s |
| x86_64 (generic) | bw=233MiB/s | bw=230MiB/s |
Using a alloc_workqueue() @max_active arg of num_online_cpus() only
made sense with WQ_UNBOUND. Switch the @max_active arg to 0 (aka
default, which is 256 per-cpu).
Also, eliminate 'wq_flags' since it really doesn't serve a purpose.
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/md/dm-verity-target.c | 6 |
1 files changed, 1 insertions, 5 deletions
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index ccf5b852fbf7..4c52b056ecf0 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -1162,7 +1162,6 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) struct dm_verity_sig_opts verify_args = {0}; struct dm_arg_set as; unsigned int num; - unsigned int wq_flags; unsigned long long num_ll; int r; int i; @@ -1399,8 +1398,6 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) goto bad; } - /* WQ_UNBOUND greatly improves performance when running on ramdisk */ - wq_flags = WQ_MEM_RECLAIM | WQ_UNBOUND; /* * Using WQ_HIGHPRI improves throughput and completion latency by * reducing wait times when reading from a dm-verity device. @@ -1410,8 +1407,7 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) * 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()); + v->verify_wq = alloc_workqueue("kverityd", WQ_MEM_RECLAIM | WQ_HIGHPRI, 0); if (!v->verify_wq) { ti->error = "Cannot allocate workqueue"; r = -ENOMEM; |