On Tue, Feb 7, 2023 at 12:16 AM Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > > On Wed, 1 Feb 2023, Nathan Huckleberry 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. > > Hi > > If you remove WQ_UNBOUND, you should also change the last argument of > alloc_workqueue from num_online_cpus() to either 0 or 1. Try both 0 and 1 > and tell us which performs better. They look roughly the same on ARM64. There's a slight advantage for using 1, but they're too close to conclusively say one is better. Thanks, Huck > > Mikulas > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
