On 18/08/17 23:31, Stefan Hajnoczi wrote:
> 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.
>
> Reported-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> Cc: Kevin Wolf <kw...@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> ---
> Alexey: Does this improve your memory profiling results?
Yes, it does:
was:
12.81% (1,023,193,088B)
now:
05.36% (393,893,888B)
Tested-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> 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..c47600a44e 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 -EIO;
> + }
> + }
> + 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 40ba26c111..0ac201910a 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;
>
--
Alexey
