On 08/18/2017 08:31 AM, 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?
Is this a regression from earlier versions? Likely, it is NOT -rc4
material, and thus can wait for 2.11; but it should be fine for -stable
as part of 2.10.1 down the road.
> +++ 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;
Is -ENOMEM any better than -EIO here?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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