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

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 6035794bc1f208809aa0175685a3a15f58fc2c7d..3d237a03dab3dbd2ead85526a76e8ddcf9271f2d 100644 (file)
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -458,6 +458,21 @@ config DM_VERITY
 
          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 @@ config DM_ANDROID_VERITY
        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 9d3d4b2972011f090696e9e9b9105a80b967e272..c7e97cf6e7fb1ac118eebe3df4350b100985ce23 100644 (file)
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -501,6 +501,7 @@ static void verity_prefetch_io(struct work_struct *work)
                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 @@ static void verity_prefetch_io(struct work_struct *work)
                                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);