On Mon, Dec 16, 2019 at 02:02:33AM +0000, xianrong.zhou(周先荣) wrote: > hey Eric: > > On Wed, Dec 11, 2019 at 11:32:40AM +0800, zhou xianrong wrote: > > From: "xianrong.zhou" <[email protected]> > > > > If check_at_most_once enabled, just like verity work the prefetching > > work should check for data block bitmap firstly before reading hash > > block as well. Skip bit-set data blocks from both ends of data block > > range by testing the validated bitmap. This can reduce the amounts of > > data blocks which need to read hash blocks. > > > > Launching 91 apps every 15s and repeat 21 rounds on Android Q. > > In prefetching work we can let only 2602/360312 = 0.72% data blocks > > really need to read hash blocks. > > > > But the reduced data blocks range would be enlarged again by > > dm_verity_prefetch_cluster later. > > > > Signed-off-by: xianrong.zhou <[email protected]> > > Signed-off-by: yuanjiong.gao <[email protected]> > > Tested-by: ruxian.feng <[email protected]> > > --- > > drivers/md/dm-verity-target.c | 16 ++++++++++++++++ > > 1 file changed, 16 insertions(+) > > > > diff --git a/drivers/md/dm-verity-target.c > > b/drivers/md/dm-verity-target.c index 4fb33e7562c5..7b8eb754c0b6 > > 100644 > > --- a/drivers/md/dm-verity-target.c > > +++ b/drivers/md/dm-verity-target.c > > @@ -581,6 +581,22 @@ static void verity_prefetch_io(struct work_struct > > *work) > > struct dm_verity *v = pw->v; > > int i; > > > > + if (v->validated_blocks) { > > + while (pw->n_blocks) { > > + if (unlikely(!test_bit(pw->block, v->validated_blocks))) > > + break; > > + pw->block++; > > + pw->n_blocks--; > > + } > > + while (pw->n_blocks) { > > + if (unlikely(!test_bit(pw->block + pw->n_blocks - 1, > > + v->validated_blocks))) > > + break; > > + pw->n_blocks--; > > + } > > + if (!pw->n_blocks) > > + return; > > + } > > This is a good idea, but shouldn't this logic go in verity_submit_prefetch() > prior to the struct dm_verity_prefetch_work being allocated? Then if no > prefeching is needed, allocating and scheduling the work object can be > skipped. > > Eric, Do you mean it is more suitable in dm_bufio_prefetch which is called on > different paths even though prefeching is disabled ? >
No, I'm talking about verity_submit_prefetch(). verity_submit_prefetch() allocates and schedules a work object, which executes verity_prefetch_io(). If all data blocks in the I/O request were already validated, there's no need to allocate and schedule the prefetch work. - Eric -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
