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[Qemu-devel] [PATCH 8/8] block-migration: efficiently encode zero blocks
From: |
Peter Lieven |
Subject: |
[Qemu-devel] [PATCH 8/8] block-migration: efficiently encode zero blocks |
Date: |
Sat, 22 Jun 2013 22:58:32 +0200 |
this patch adds a efficient encoding for zero blocks by
adding a new flag indiciating a block is completly zero.
additionally bdrv_write_zeros() is used at the destination
to efficiently write these zeroes. if the driver supports
it this avoids blindly allocating all sectors consumed by
zero blocks effectively re-thinning the device.
Signed-off-by: Peter Lieven <address@hidden>
---
block-migration.c | 29 +++++++++++++++++++++++------
include/migration/qemu-file.h | 1 +
savevm.c | 2 +-
3 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/block-migration.c b/block-migration.c
index 2fd7699..99b3757 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -29,6 +29,7 @@
#define BLK_MIG_FLAG_DEVICE_BLOCK 0x01
#define BLK_MIG_FLAG_EOS 0x02
#define BLK_MIG_FLAG_PROGRESS 0x04
+#define BLK_MIG_FLAG_ZERO_BLOCK 0x08
#define MAX_IS_ALLOCATED_SEARCH 65536
@@ -114,16 +115,29 @@ static void blk_mig_unlock(void)
static void blk_send(QEMUFile *f, BlkMigBlock * blk)
{
int len;
+ int flags = BLK_MIG_FLAG_DEVICE_BLOCK;
+
+ if (buffer_is_zero(blk->buf, BLOCK_SIZE)) {
+ flags |= BLK_MIG_FLAG_ZERO_BLOCK;
+ }
/* sector number and flags */
qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)
- | BLK_MIG_FLAG_DEVICE_BLOCK);
+ | flags);
/* device name */
len = strlen(blk->bmds->bs->device_name);
qemu_put_byte(f, len);
qemu_put_buffer(f, (uint8_t *)blk->bmds->bs->device_name, len);
+ /* if a block is zero we need to flush here since the network
+ * bandwidth is now a lot higher than the storage device bandwidth.
+ * thus if we queue zero blocks we slow down the migration */
+ if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
+ qemu_fflush(f);
+ return;
+ }
+
qemu_put_buffer(f, blk->buf, BLOCK_SIZE);
}
@@ -762,12 +776,15 @@ static int block_load(QEMUFile *f, void *opaque, int
version_id)
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
}
- buf = g_malloc(BLOCK_SIZE);
-
- qemu_get_buffer(f, buf, BLOCK_SIZE);
- ret = bdrv_write(bs, addr, buf, nr_sectors);
+ if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
+ ret = bdrv_write_zeroes(bs, addr, nr_sectors);
+ } else {
+ buf = g_malloc(BLOCK_SIZE);
+ qemu_get_buffer(f, buf, BLOCK_SIZE);
+ ret = bdrv_write(bs, addr, buf, nr_sectors);
+ g_free(buf);
+ }
- g_free(buf);
if (ret < 0) {
return ret;
}
diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 7519464..b73298d 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -71,6 +71,7 @@ QEMUFile *qemu_fdopen(int fd, const char *mode);
QEMUFile *qemu_fopen_socket(int fd, const char *mode);
QEMUFile *qemu_popen_cmd(const char *command, const char *mode);
int qemu_get_fd(QEMUFile *f);
+void qemu_fflush(QEMUFile *f);
int qemu_fclose(QEMUFile *f);
int64_t qemu_ftell(QEMUFile *f);
void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size);
diff --git a/savevm.c b/savevm.c
index ff5ece6..4d12d92 100644
--- a/savevm.c
+++ b/savevm.c
@@ -610,7 +610,7 @@ static inline bool qemu_file_is_writable(QEMUFile *f)
* If there is writev_buffer QEMUFileOps it uses it otherwise uses
* put_buffer ops.
*/
-static void qemu_fflush(QEMUFile *f)
+void qemu_fflush(QEMUFile *f)
{
ssize_t ret = 0;
--
1.7.9.5
- Re: [Qemu-devel] [PATCH 6/8] qemu-img: use bdrv_write_zeroes to write zeroes, (continued)
- [Qemu-devel] [PATCH 5/8] block/raw: add bdrv_co_write_zeroes, Peter Lieven, 2013/06/22
- [Qemu-devel] [PATCH 4/8] block: add bdrv_write_zeroes(), Peter Lieven, 2013/06/22
- [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize, Peter Lieven, 2013/06/22
- Re: [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize, Paolo Bonzini, 2013/06/24
- Re: [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize, Peter Lieven, 2013/06/24
- Re: [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize, Paolo Bonzini, 2013/06/24
- Re: [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize, Peter Lieven, 2013/06/24
- Re: [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize, Paolo Bonzini, 2013/06/24
- Re: [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize, Peter Lieven, 2013/06/24
[Qemu-devel] [PATCH 8/8] block-migration: efficiently encode zero blocks,
Peter Lieven <=