On 2025/4/2 17:56, Mikulas Patocka wrote:
On Wed, 2 Apr 2025, LongPing Wei wrote:
At this time, all bios for hash blocks should eventually
be merged into a single large bio.
Signed-off-by: LongPing Wei <weilongp...@oppo.com>
---
drivers/md/dm-verity-target.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 3c427f18a04b..813d5cfc7ffa 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -1683,6 +1683,10 @@ static int verity_ctr(struct dm_target *ti, unsigned int
argc, char **argv)
verity_verify_sig_opts_cleanup(&verify_args);
+ dm_bufio_prefetch_with_ioprio(v->bufio, v->hash_start,
+ v->hash_blocks - v->hash_start,
+ IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 0));
+
dm_audit_log_ctr(DM_MSG_PREFIX, ti, 1);
return 0;
--
2.34.1
Hi
I would move it into the "resume" callback, so that if the user
reconfigures the device stack between "ctr" and "resume", it won't read
the data too early.
Don't use IOPRIO_CLASS_RT, this is not real-time requirement,
IOPRIO_CLASS_RT would slow down concurrent I/O.
If the prefetch io is submitted with non-rt at first, the later dm io
need the same hash block will wait the non-rt bio.
Another problem with this approach is that when the verity device is big
and system memory is small, it just causes I/O churn - new bufio blocks
will be displacing old blocks - and it will degrade performance, not
improve it.
Do we need a solution to check if the memory is enough to the prefetch?
For Android devices, the verity device should be created on the boot
procedure.
Please, describe some scenario, where this prefetch actually helps. What
is the size of the metadata that you are prefetching? What is the total
memory size? Is there any benchmark that shows the advantage of this
patch?
The size of hash blocks for the ROM of our low-end devices is about
71MiB. I want to enhance probability of cache hit when
try_verify_in_tasklet is enabled. How about only doing the prefetch when
try_verify_in_tasklet is enabled?
For example:
if (v->use_bh_wq)
dm_bufio_prefetch_with_ioprio(v->bufio, v->hash_start,
v->hash_blocks - v->hash_start,
IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 0));
Mikulas
LongPing
