ping
06.02.2019 15:30, Vladimir Sementsov-Ogievskiy wrote:
> ping.
>
> Finally, what about this?
>
> 25.01.2019 17:21, Vladimir Sementsov-Ogievskiy wrote:
>> drv_co_block_status digs bs->file for additional, more accurate search
>> for hole inside region, reported as DATA by bs since 5daa74a6ebc.
>>
>> This accuracy is not free: assume we have qcow2 disk. Actually, qcow2
>> knows, where are holes and where is data. But every block_status
>> request calls lseek additionally. Assume a big disk, full of
>> data, in any iterative copying block job (or img convert) we'll call
>> lseek(HOLE) on every iteration, and each of these lseeks will have to
>> iterate through all metadata up to the end of file. It's obviously
>> ineffective behavior. And for many scenarios we don't need this lseek
>> at all.
>>
>> However, lseek is needed when we have metadata-preallocated image.
>>
>> So, let's detect metadata-preallocation case and don't dig qcow2's
>> protocol file in other cases.
>>
>> The idea is to compare allocation size in POV of filesystem with
>> allocations size in POV of Qcow2 (by refcounts). If allocation in fs is
>> significantly lower, consider it as metadata-preallocation case.
>>
>> Suggested-by: Denis V. Lunev <d...@openvz.org>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
>> ---
>>
>> Hi!
>>
>> So, to continue talk about lseek/no lseek when qcow2 block_status reports
>> DATA.
>>
>> Results on tmpfs:
>> cached is lseek cache by Kevin
>> detect is this patch
>> no lseek is just remove block_status query on bs->file->bs in
>> bdrv_co_block_status
>>
>> +---------------------+--------+--------+--------+----------+
>> | | master | cached | detect | no lseek |
>> +---------------------+--------+--------+--------+----------+
>> | test.qcow2 | 80 | 40 | 0.169 | 0.162 |
>> +---------------------+--------+--------+--------+----------+
>> | test_forward.qcow2 | 79 | 0.171 | 0.169 | 0.163 |
>> +---------------------+--------+--------+--------+----------+
>> | test_prealloc.qcow2 | 0.054 | 0.053 | 0.055 | 0.263 |
>> +---------------------+--------+--------+--------+----------+
>>
>> block/qcow2.h | 1 +
>> include/block/block_int.h | 7 +++++++
>> block/io.c | 3 ++-
>> block/qcow2-refcount.c | 36 ++++++++++++++++++++++++++++++++++++
>> block/qcow2.c | 7 +++++++
>> 5 files changed, 53 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/qcow2.h b/block/qcow2.h
>> index 438a1dee9e..d7113ed44c 100644
>> --- a/block/qcow2.h
>> +++ b/block/qcow2.h
>> @@ -610,6 +610,7 @@ int qcow2_change_refcount_order(BlockDriverState *bs,
>> int refcount_order,
>> void *cb_opaque, Error **errp);
>> int qcow2_shrink_reftable(BlockDriverState *bs);
>> int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size);
>> +int qcow2_detect_metadata_preallocation(BlockDriverState *bs);
>> /* qcow2-cluster.c functions */
>> int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
>> diff --git a/include/block/block_int.h b/include/block/block_int.h
>> index f605622216..c895ca7169 100644
>> --- a/include/block/block_int.h
>> +++ b/include/block/block_int.h
>> @@ -59,6 +59,12 @@
>> #define BLOCK_PROBE_BUF_SIZE 512
>> +typedef enum BdrvYesNoUnknown {
>> + BDRV_UNKNOWN = 0,
>> + BDRV_NO,
>> + BDRV_YES,
>> +} BdrvYesNoUnknown;
>> +
>> enum BdrvTrackedRequestType {
>> BDRV_TRACKED_READ,
>> BDRV_TRACKED_WRITE,
>> @@ -682,6 +688,7 @@ struct BlockDriverState {
>> bool probed; /* if true, format was probed rather than specified */
>> bool force_share; /* if true, always allow all shared permissions */
>> bool implicit; /* if true, this filter node was automatically
>> inserted */
>> + BdrvYesNoUnknown metadata_preallocation;
>> BlockDriver *drv; /* NULL means no media */
>> void *opaque;
>> diff --git a/block/io.c b/block/io.c
>> index bd9d688f8b..815661750a 100644
>> --- a/block/io.c
>> +++ b/block/io.c
>> @@ -2186,7 +2186,8 @@ static int coroutine_fn
>> bdrv_co_block_status(BlockDriverState *bs,
>> }
>> }
>> - if (want_zero && local_file && local_file != bs &&
>> + if (want_zero && bs->metadata_preallocation != BDRV_NO &&
>> + local_file && local_file != bs &&
>> (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
>> (ret & BDRV_BLOCK_OFFSET_VALID)) {
>> int64_t file_pnum;
>> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
>> index 1c63ac244a..008196d849 100644
>> --- a/block/qcow2-refcount.c
>> +++ b/block/qcow2-refcount.c
>> @@ -3379,3 +3379,39 @@ int64_t qcow2_get_last_cluster(BlockDriverState *bs,
>> int64_t size)
>> "There are no references in the refcount
>> table.");
>> return -EIO;
>> }
>> +
>> +int qcow2_detect_metadata_preallocation(BlockDriverState *bs)
>> +{
>> + BDRVQcow2State *s = bs->opaque;
>> + int64_t i, end_cluster, cluster_count = 0;
>> + int64_t file_length, real_allocation, metadata_allocation, file_tail;
>> + uint64_t refcount;
>> +
>> + file_length = bdrv_getlength(bs->file->bs);
>> + if (file_length < 0) {
>> + return file_length;
>> + }
>> + file_tail = offset_into_cluster(s, file_length);
>> +
>> + real_allocation = bdrv_get_allocated_file_size(bs->file->bs);
>> + if (real_allocation < 0) {
>> + return real_allocation;
>> + }
>> +
>> + end_cluster = size_to_clusters(s, file_length);
>> + for (i = 0; i < end_cluster; i++) {
>> + int ret = qcow2_get_refcount(bs, i, &refcount);
>> + if (ret < 0) {
>> + return ret;
>> + }
>> + cluster_count += !!refcount;
>> + }
>> +
>> + metadata_allocation = cluster_count * s->cluster_size;
>> + if (!!refcount && file_tail) {
>> + metadata_allocation -= s->cluster_size - file_tail;
>> + }
>> +
>> + return real_allocation < 0.9 * metadata_allocation &&
>> + real_allocation + s->cluster_size < metadata_allocation;
>> +}
>> diff --git a/block/qcow2.c b/block/qcow2.c
>> index 4897abae5e..adc9cdcb27 100644
>> --- a/block/qcow2.c
>> +++ b/block/qcow2.c
>> @@ -1800,6 +1800,13 @@ static int coroutine_fn
>> qcow2_co_block_status(BlockDriverState *bs,
>> unsigned int bytes;
>> int status = 0;
>> + if (bs->metadata_preallocation == BDRV_UNKNOWN) {
>> + ret = qcow2_detect_metadata_preallocation(bs);
>> + if (ret >= 0) {
>> + bs->metadata_preallocation = ret ? BDRV_YES : BDRV_NO;
>> + }
>> + }
>> +
>> bytes = MIN(INT_MAX, count);
>> qemu_co_mutex_lock(&s->lock);
>> ret = qcow2_get_cluster_offset(bs, offset, &bytes, &cluster_offset);
>>
>
>
--
Best regards,
Vladimir
