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Commit a7b3e50c authored by Keun-young Park's avatar Keun-young Park
Browse files

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: default avatarKeun-young Park <keunyoung@google.com>
parent 6193f2fa

drivers/md/Kconfig

+16 −0
Original line number Diff line number Diff line
@@ -418,6 +418,21 @@ 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_ANDROID_VERITY

	tristate "Android verity target support"

	depends on DM_VERITY
@@ -428,6 +443,7 @@ 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

drivers/md/dm-verity-target.c

+8 −1
Original line number Diff line number Diff line
@@ -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:

		dm_bufio_prefetch(v->bufio, hash_block_start,

		// 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,

				  prefetch_size);

	}



	kfree(pw);