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[Qemu-devel] [PULL 20/42] cow: make writes go at a less indecent speed
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PULL 20/42] cow: make writes go at a less indecent speed |
Date: |
Fri, 6 Sep 2013 17:38:51 +0200 |
From: Paolo Bonzini <address@hidden>
Only sync once per write, rather than once per sector.
Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block/cow.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/block/cow.c b/block/cow.c
index 4512806..cd889e6 100644
--- a/block/cow.c
+++ b/block/cow.c
@@ -106,7 +106,7 @@ static int cow_open(BlockDriverState *bs, QDict *options,
int flags)
* XXX(hch): right now these functions are extremely inefficient.
* We should just read the whole bitmap we'll need in one go instead.
*/
-static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
+static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum, bool
*first)
{
uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
uint8_t bitmap;
@@ -117,9 +117,21 @@ static inline int cow_set_bit(BlockDriverState *bs,
int64_t bitnum)
return ret;
}
+ if (bitmap & (1 << (bitnum % 8))) {
+ return 0;
+ }
+
+ if (*first) {
+ ret = bdrv_flush(bs->file);
+ if (ret < 0) {
+ return ret;
+ }
+ *first = false;
+ }
+
bitmap |= (1 << (bitnum % 8));
- ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap));
+ ret = bdrv_pwrite(bs->file, offset, &bitmap, sizeof(bitmap));
if (ret < 0) {
return ret;
}
@@ -181,9 +193,10 @@ static int cow_update_bitmap(BlockDriverState *bs, int64_t
sector_num,
{
int error = 0;
int i;
+ bool first = true;
for (i = 0; i < nb_sectors; i++) {
- error = cow_set_bit(bs, sector_num + i);
+ error = cow_set_bit(bs, sector_num + i, &first);
if (error) {
break;
}
--
1.8.3.1
- [Qemu-devel] [PULL 34/42] qemu-img: add a "map" subcommand, (continued)
- [Qemu-devel] [PULL 34/42] qemu-img: add a "map" subcommand, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 35/42] docs, qapi: document qemu-img map, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 36/42] raw-posix: return get_block_status data and flags, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 37/42] raw-posix: report unwritten extents as zero, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 38/42] block: add default get_block_status implementation for protocols, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 39/42] block: look for zero blocks in bs->file, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 40/42] dataplane: Fix startup race., Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 41/42] qemu-iotests: Whitespace cleanup, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 42/42] qemu-iotests: Fixed test case 026, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 18/42] qmp: Documentation for BLOCK_IMAGE_CORRUPTED, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 20/42] cow: make writes go at a less indecent speed,
Stefan Hajnoczi <=
- [Qemu-devel] [PULL 16/42] nbd: use BlockDriverState refcnt, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 25/42] block: remove bdrv_is_allocated_above/bdrv_co_is_allocated_above distinction, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 26/42] block: expect errors from bdrv_co_is_allocated, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 22/42] block: keep bs->total_sectors up to date even for growable block devices, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 23/42] block: make bdrv_co_is_allocated static, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 21/42] cow: do not call bdrv_co_is_allocated, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 24/42] block: do not use ->total_sectors in bdrv_co_is_allocated, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 19/42] cow: make reads go at a decent speed, Stefan Hajnoczi, 2013/09/06
- [Qemu-devel] [PULL 17/42] block: use BDS ref for block jobs, Stefan Hajnoczi, 2013/09/06