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[Qemu-devel] [PULL for-2.10 15/15] qcow2: allocate cluster_cache/cluster
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PULL for-2.10 15/15] qcow2: allocate cluster_cache/cluster_data on demand |
Date: |
Thu, 31 Aug 2017 09:22:10 +0100 |
Most qcow2 files are uncompressed so it is wasteful to allocate (32 + 1)
* cluster_size + 512 bytes upfront. Allocate s->cluster_cache and
s->cluster_data when the first read operation is performance on a
compressed cluster.
The buffers are freed in .bdrv_close(). .bdrv_open() no longer has any
code paths that can allocate these buffers, so remove the free functions
in the error code path.
This patch can result in significant memory savings when many qcow2
disks are attached or backing file chains are long:
Before 12.81% (1,023,193,088B)
After 5.36% (393,893,888B)
Reported-by: Alexey Kardashevskiy <address@hidden>
Tested-by: Alexey Kardashevskiy <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
Message-id: address@hidden
Cc: Kevin Wolf <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block/qcow2-cluster.c | 17 +++++++++++++++++
block/qcow2.c | 12 ------------
2 files changed, 17 insertions(+), 12 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index f06c08f64c..8538533102 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1516,6 +1516,23 @@ int qcow2_decompress_cluster(BlockDriverState *bs,
uint64_t cluster_offset)
nb_csectors = ((cluster_offset >> s->csize_shift) & s->csize_mask) + 1;
sector_offset = coffset & 511;
csize = nb_csectors * 512 - sector_offset;
+
+ /* Allocate buffers on first decompress operation, most images are
+ * uncompressed and the memory overhead can be avoided. The buffers
+ * are freed in .bdrv_close().
+ */
+ if (!s->cluster_data) {
+ /* one more sector for decompressed data alignment */
+ s->cluster_data = qemu_try_blockalign(bs->file->bs,
+ QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size + 512);
+ if (!s->cluster_data) {
+ return -ENOMEM;
+ }
+ }
+ if (!s->cluster_cache) {
+ s->cluster_cache = g_malloc(s->cluster_size);
+ }
+
BLKDBG_EVENT(bs->file, BLKDBG_READ_COMPRESSED);
ret = bdrv_read(bs->file, coffset >> 9, s->cluster_data,
nb_csectors);
diff --git a/block/qcow2.c b/block/qcow2.c
index fbfffadc76..a3679c69e8 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1360,16 +1360,6 @@ static int qcow2_do_open(BlockDriverState *bs, QDict
*options, int flags,
goto fail;
}
- s->cluster_cache = g_malloc(s->cluster_size);
- /* one more sector for decompressed data alignment */
- s->cluster_data = qemu_try_blockalign(bs->file->bs, QCOW_MAX_CRYPT_CLUSTERS
- * s->cluster_size + 512);
- if (s->cluster_data == NULL) {
- error_setg(errp, "Could not allocate temporary cluster buffer");
- ret = -ENOMEM;
- goto fail;
- }
-
s->cluster_cache_offset = -1;
s->flags = flags;
@@ -1507,8 +1497,6 @@ static int qcow2_do_open(BlockDriverState *bs, QDict
*options, int flags,
if (s->refcount_block_cache) {
qcow2_cache_destroy(bs, s->refcount_block_cache);
}
- g_free(s->cluster_cache);
- qemu_vfree(s->cluster_data);
qcrypto_block_free(s->crypto);
qapi_free_QCryptoBlockOpenOptions(s->crypto_opts);
return ret;
--
2.13.5
- [Qemu-devel] [PULL for-2.10 05/15] throttle: Remove throttle_fix_bucket() / throttle_unfix_bucket(), (continued)
- [Qemu-devel] [PULL for-2.10 05/15] throttle: Remove throttle_fix_bucket() / throttle_unfix_bucket(), Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 06/15] throttle: Make LeakyBucket.avg and LeakyBucket.max integer types, Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 07/15] throttle: Make burst_length 64bit and add range checks, Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 08/15] throttle: Test the valid range of config values, Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 09/15] oslib-posix: Print errors before aborting on qemu_alloc_stack(), Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 10/15] misc: Remove unused Error variables, Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 12/15] docker.py: Python 2.6 argparse compatibility, Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 13/15] tests: migration/guestperf Python 2.6 argparse compatibility, Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 14/15] qemu-doc: Add UUID support in initiator name, Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 11/15] scripts: add argparse module for Python 2.6 compatibility, Stefan Hajnoczi, 2017/08/31
- [Qemu-devel] [PULL for-2.10 15/15] qcow2: allocate cluster_cache/cluster_data on demand,
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PULL for-2.10 00/15] Block patches, no-reply, 2017/08/31
- Re: [Qemu-devel] [PULL for-2.10 00/15] Block patches, Eric Blake, 2017/08/31
- Re: [Qemu-devel] [PULL for-2.10 00/15] Block patches, Peter Maydell, 2017/08/31