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 | Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx> Cc: Eric Biggers <ebiggers@xxxxxxxxxx> Signed-off-by: Nathan Huckleberry <nhuck@xxxxxxxxxx> --- drivers/md/dm-verity-target.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index ccf5b852fbf7..020fd2341025 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -1399,8 +1399,8 @@ 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; + wq_flags = WQ_MEM_RECLAIM; + /* * Using WQ_HIGHPRI improves throughput and completion latency by * reducing wait times when reading from a dm-verity device. -- 2.39.1.456.gfc5497dd1b-goog -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
