ANDROID: dm verity: add minimum prefetch size
- For device like eMMC, it gives better performance to read more hash
blocks at a time.
- For android, set it to default 128.
For other devices, set it to 1 which is the same as now.
- saved boot-up time by 300ms in tested device
bug: 32246564
Change-Id: Ibc0401a0cddba64b862a80445844b4e595213621
Cc: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Keun-young Park <keunyoung@google.com>
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index f550da3..1e66909 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -458,6 +458,21 @@
If unsure, say N.
+config DM_VERITY_HASH_PREFETCH_MIN_SIZE_128
+ bool "Prefetch size 128"
+
+config DM_VERITY_HASH_PREFETCH_MIN_SIZE
+ int "Verity hash prefetch minimum size"
+ depends on DM_VERITY
+ range 1 4096
+ default 128 if DM_VERITY_HASH_PREFETCH_MIN_SIZE_128
+ default 1
+ ---help---
+ This sets minimum number of hash blocks to prefetch for dm-verity.
+ For devices like eMMC, having larger prefetch size like 128 can improve
+ performance with increased memory consumption for keeping more hashes
+ in RAM.
+
config DM_VERITY_FEC
bool "Verity forward error correction support"
depends on DM_VERITY
@@ -510,6 +525,7 @@
depends on ASYMMETRIC_KEY_TYPE
depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE
depends on MD_LINEAR
+ select DM_VERITY_HASH_PREFETCH_MIN_SIZE_128
---help---
This device-mapper target is virtually a VERITY target. This
target is setup by reading the metadata contents piggybacked
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index b53539e..5d0a996 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -501,6 +501,7 @@
container_of(work, struct dm_verity_prefetch_work, work);
struct dm_verity *v = pw->v;
int i;
+ sector_t prefetch_size;
for (i = v->levels - 2; i >= 0; i--) {
sector_t hash_block_start;
@@ -523,8 +524,14 @@
hash_block_end = v->hash_blocks - 1;
}
no_prefetch_cluster:
+ // for emmc, it is more efficient to send bigger read
+ prefetch_size = max((sector_t)CONFIG_DM_VERITY_HASH_PREFETCH_MIN_SIZE,
+ hash_block_end - hash_block_start + 1);
+ if ((hash_block_start + prefetch_size) >= (v->hash_start + v->hash_blocks)) {
+ prefetch_size = hash_block_end - hash_block_start + 1;
+ }
dm_bufio_prefetch(v->bufio, hash_block_start,
- hash_block_end - hash_block_start + 1);
+ prefetch_size);
}
kfree(pw);