On Wed, Feb 01 2023 at 8:23P -0500, Nathan Huckleberry <nhuck@xxxxxxxxxx> wrote: > 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 Hi, I've discussed with Mikulas, tweaked your patch slightly but accepted your change, please see: https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-6.3&id=6f30cc248507ee96c22ff4c3cbc86099ff12b7a9 Thanks, Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
