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[Qemu-devel] [PULL 44/54] block: use 1 MB bounce buffers for crypto inst
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 44/54] block: use 1 MB bounce buffers for crypto instead of 16KB |
Date: |
Fri, 6 Oct 2017 17:54:12 +0200 |
From: "Daniel P. Berrange" <address@hidden>
Using 16KB bounce buffers creates a significant performance
penalty for I/O to encrypted volumes on storage which high
I/O latency (rotating rust & network drives), because it
triggers lots of fairly small I/O operations.
On tests with rotating rust, and cache=none|directsync,
write speed increased from 2MiB/s to 32MiB/s, on a par
with that achieved by the in-kernel luks driver. With
other cache modes the in-kernel driver is still notably
faster because it is able to report completion of the
I/O request before any encryption is done, while the
in-QEMU driver must encrypt the data before completion.
Signed-off-by: Daniel P. Berrange <address@hidden>
Message-id: address@hidden
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Signed-off-by: Max Reitz <address@hidden>
---
block/crypto.c | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)
diff --git a/block/crypto.c b/block/crypto.c
index 58ef6f2f52..684cabeaf8 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -379,7 +379,11 @@ static void block_crypto_close(BlockDriverState *bs)
}
-#define BLOCK_CRYPTO_MAX_SECTORS 32
+/*
+ * 1 MB bounce buffer gives good performance / memory tradeoff
+ * when using cache=none|directsync.
+ */
+#define BLOCK_CRYPTO_MAX_IO_SIZE (1024 * 1024)
static coroutine_fn int
block_crypto_co_readv(BlockDriverState *bs, int64_t sector_num,
@@ -396,12 +400,11 @@ block_crypto_co_readv(BlockDriverState *bs, int64_t
sector_num,
qemu_iovec_init(&hd_qiov, qiov->niov);
- /* Bounce buffer so we have a linear mem region for
- * entire sector. XXX optimize so we avoid bounce
- * buffer in case that qiov->niov == 1
+ /* Bounce buffer because we don't wish to expose cipher text
+ * in qiov which points to guest memory.
*/
cipher_data =
- qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_SECTORS * 512,
+ qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_IO_SIZE,
qiov->size));
if (cipher_data == NULL) {
ret = -ENOMEM;
@@ -411,8 +414,8 @@ block_crypto_co_readv(BlockDriverState *bs, int64_t
sector_num,
while (remaining_sectors) {
cur_nr_sectors = remaining_sectors;
- if (cur_nr_sectors > BLOCK_CRYPTO_MAX_SECTORS) {
- cur_nr_sectors = BLOCK_CRYPTO_MAX_SECTORS;
+ if (cur_nr_sectors > (BLOCK_CRYPTO_MAX_IO_SIZE / 512)) {
+ cur_nr_sectors = (BLOCK_CRYPTO_MAX_IO_SIZE / 512);
}
qemu_iovec_reset(&hd_qiov);
@@ -464,12 +467,11 @@ block_crypto_co_writev(BlockDriverState *bs, int64_t
sector_num,
qemu_iovec_init(&hd_qiov, qiov->niov);
- /* Bounce buffer so we have a linear mem region for
- * entire sector. XXX optimize so we avoid bounce
- * buffer in case that qiov->niov == 1
+ /* Bounce buffer because we're not permitted to touch
+ * contents of qiov - it points to guest memory.
*/
cipher_data =
- qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_SECTORS * 512,
+ qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_IO_SIZE,
qiov->size));
if (cipher_data == NULL) {
ret = -ENOMEM;
@@ -479,8 +481,8 @@ block_crypto_co_writev(BlockDriverState *bs, int64_t
sector_num,
while (remaining_sectors) {
cur_nr_sectors = remaining_sectors;
- if (cur_nr_sectors > BLOCK_CRYPTO_MAX_SECTORS) {
- cur_nr_sectors = BLOCK_CRYPTO_MAX_SECTORS;
+ if (cur_nr_sectors > (BLOCK_CRYPTO_MAX_IO_SIZE / 512)) {
+ cur_nr_sectors = (BLOCK_CRYPTO_MAX_IO_SIZE / 512);
}
qemu_iovec_to_buf(qiov, bytes_done,
--
2.13.6
- [Qemu-devel] [PULL 35/54] qemu-iotests: Allow QMP pretty printing in common.qemu, (continued)
- [Qemu-devel] [PULL 35/54] qemu-iotests: Allow QMP pretty printing in common.qemu, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 34/54] commit: Support multiple roots above top node, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 32/54] qemu-iotests: merge "check" and "common", Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 38/54] qemu-io: Add -C for opening with copy-on-read, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 37/54] commit: Remove overlay_bs, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 40/54] iotests: Restore stty settings on completion, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 46/54] block: fix data type casting for crypto payload offset, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 45/54] crypto: expose encryption sector size in APIs, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 41/54] block: Add blkdebug hook for copy-on-read, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 42/54] block: Perform copy-on-read in loop, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 44/54] block: use 1 MB bounce buffers for crypto instead of 16KB,
Kevin Wolf <=
- [Qemu-devel] [PULL 36/54] qemu-iotests: Test commit block job where top has two parents, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 43/54] iotests: Add test 197 for covering copy-on-read, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 47/54] block: convert crypto driver to bdrv_co_preadv|pwritev, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 50/54] block/mirror: check backing in bdrv_mirror_top_refresh_filename, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 48/54] block: convert qcrypto_block_encrypt|decrypt to take bytes offset, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 51/54] iotests: Fix 195 if IMGFMT is part of TEST_DIR, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 49/54] block: support passthrough of BDRV_REQ_FUA in crypto driver, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 53/54] qcow2: truncate the tail of the image file after shrinking the image, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 54/54] block/mirror: check backing in bdrv_mirror_top_flush, Kevin Wolf, 2017/10/06
- [Qemu-devel] [PULL 52/54] qcow2: fix return error code in qcow2_truncate(), Kevin Wolf, 2017/10/06