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| author | Max Reitz <mreitz@redhat.com> | 2014-08-18 22:07:31 +0200 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2014-08-20 11:51:28 +0200 |
| commit | 440ba08aea3d841996efaf6a6b88426b0d59abf4 (patch) | |
| tree | 43d6edcbbb02d93890e70c2ae3025ce320db7a99 /block | |
| parent | 18a7d0c56e1377f3d5fa1dc4d78a15dbab01cd83 (diff) | |
| download | qemu-440ba08aea3d841996efaf6a6b88426b0d59abf4.zip qemu-440ba08aea3d841996efaf6a6b88426b0d59abf4.tar.gz qemu-440ba08aea3d841996efaf6a6b88426b0d59abf4.tar.bz2 | |
qcow2: Constant cache size in bytes
Specifying the metadata cache sizes in clusters results in less clusters
(and much less bytes) covered for small cluster sizes and vice versa.
Using a constant byte size reduces this difference, and makes it
possible to manually specify the cache size in an easily comprehensible
unit.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/qcow2.c | 15 | ||||
| -rw-r--r-- | block/qcow2.h | 10 |
2 files changed, 21 insertions, 4 deletions
diff --git a/block/qcow2.c b/block/qcow2.c index 435e0e1..0f1be2e 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -470,6 +470,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, uint64_t l1_vm_state_index; const char *opt_overlap_check; int overlap_check_template = 0; + uint64_t l2_cache_size, refcount_cache_size; ret = bdrv_pread(bs->file, 0, &header, sizeof(header)); if (ret < 0) { @@ -707,8 +708,18 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, } /* alloc L2 table/refcount block cache */ - s->l2_table_cache = qcow2_cache_create(bs, L2_CACHE_SIZE); - s->refcount_block_cache = qcow2_cache_create(bs, REFCOUNT_CACHE_SIZE); + l2_cache_size = DEFAULT_L2_CACHE_BYTE_SIZE / s->cluster_size; + if (l2_cache_size < MIN_L2_CACHE_SIZE) { + l2_cache_size = MIN_L2_CACHE_SIZE; + } + + refcount_cache_size = l2_cache_size / DEFAULT_L2_REFCOUNT_SIZE_RATIO; + if (refcount_cache_size < MIN_REFCOUNT_CACHE_SIZE) { + refcount_cache_size = MIN_REFCOUNT_CACHE_SIZE; + } + + s->l2_table_cache = qcow2_cache_create(bs, l2_cache_size); + s->refcount_block_cache = qcow2_cache_create(bs, refcount_cache_size); if (s->l2_table_cache == NULL || s->refcount_block_cache == NULL) { error_setg(errp, "Could not allocate metadata caches"); ret = -ENOMEM; diff --git a/block/qcow2.h b/block/qcow2.h index b49424b..671783d 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -64,10 +64,16 @@ #define MIN_CLUSTER_BITS 9 #define MAX_CLUSTER_BITS 21 -#define L2_CACHE_SIZE 16 +#define MIN_L2_CACHE_SIZE 1 /* cluster */ /* Must be at least 4 to cover all cases of refcount table growth */ -#define REFCOUNT_CACHE_SIZE 4 +#define MIN_REFCOUNT_CACHE_SIZE 4 /* clusters */ + +#define DEFAULT_L2_CACHE_BYTE_SIZE 1048576 /* bytes */ + +/* The refblock cache needs only a fourth of the L2 cache size to cover as many + * clusters */ +#define DEFAULT_L2_REFCOUNT_SIZE_RATIO 4 #define DEFAULT_CLUSTER_SIZE 65536 |