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block/qcow2: introduce parallel subrequest handling in read and write
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It improves performance for fragmented qcow2 images.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190916175324.18478-6-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
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@XanClic
Vladimir Sementsov-Ogievskiy authored and XanClic committed Oct 10, 2019
1 parent 6aa7a26 commit d710cf5
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Showing 3 changed files with 117 additions and 12 deletions.
125 changes: 113 additions & 12 deletions block/qcow2.c
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@
#include "qapi/qobject-input-visitor.h"
#include "qapi/qapi-visit-block-core.h"
#include "crypto.h"
#include "block/aio_task.h"

/*
Differences with QCOW:
Expand Down Expand Up @@ -2025,6 +2026,60 @@ qcow2_co_preadv_encrypted(BlockDriverState *bs,
return ret;
}

typedef struct Qcow2AioTask {
AioTask task;

BlockDriverState *bs;
QCow2ClusterType cluster_type; /* only for read */
uint64_t file_cluster_offset;
uint64_t offset;
uint64_t bytes;
QEMUIOVector *qiov;
uint64_t qiov_offset;
QCowL2Meta *l2meta; /* only for write */
} Qcow2AioTask;

static coroutine_fn int qcow2_co_preadv_task_entry(AioTask *task);
static coroutine_fn int qcow2_add_task(BlockDriverState *bs,
AioTaskPool *pool,
AioTaskFunc func,
QCow2ClusterType cluster_type,
uint64_t file_cluster_offset,
uint64_t offset,
uint64_t bytes,
QEMUIOVector *qiov,
size_t qiov_offset,
QCowL2Meta *l2meta)
{
Qcow2AioTask local_task;
Qcow2AioTask *task = pool ? g_new(Qcow2AioTask, 1) : &local_task;

*task = (Qcow2AioTask) {
.task.func = func,
.bs = bs,
.cluster_type = cluster_type,
.qiov = qiov,
.file_cluster_offset = file_cluster_offset,
.offset = offset,
.bytes = bytes,
.qiov_offset = qiov_offset,
.l2meta = l2meta,
};

trace_qcow2_add_task(qemu_coroutine_self(), bs, pool,
func == qcow2_co_preadv_task_entry ? "read" : "write",
cluster_type, file_cluster_offset, offset, bytes,
qiov, qiov_offset);

if (!pool) {
return func(&task->task);
}

aio_task_pool_start_task(pool, &task->task);

return 0;
}

static coroutine_fn int qcow2_co_preadv_task(BlockDriverState *bs,
QCow2ClusterType cluster_type,
uint64_t file_cluster_offset,
Expand Down Expand Up @@ -2074,18 +2129,28 @@ static coroutine_fn int qcow2_co_preadv_task(BlockDriverState *bs,
g_assert_not_reached();
}

static coroutine_fn int qcow2_co_preadv_task_entry(AioTask *task)
{
Qcow2AioTask *t = container_of(task, Qcow2AioTask, task);

assert(!t->l2meta);

return qcow2_co_preadv_task(t->bs, t->cluster_type, t->file_cluster_offset,
t->offset, t->bytes, t->qiov, t->qiov_offset);
}

static coroutine_fn int qcow2_co_preadv_part(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov,
size_t qiov_offset, int flags)
{
BDRVQcow2State *s = bs->opaque;
int ret;
int ret = 0;
unsigned int cur_bytes; /* number of bytes in current iteration */
uint64_t cluster_offset = 0;
AioTaskPool *aio = NULL;

while (bytes != 0) {

while (bytes != 0 && aio_task_pool_status(aio) == 0) {
/* prepare next request */
cur_bytes = MIN(bytes, INT_MAX);
if (s->crypto) {
Expand All @@ -2097,7 +2162,7 @@ static coroutine_fn int qcow2_co_preadv_part(BlockDriverState *bs,
ret = qcow2_get_cluster_offset(bs, offset, &cur_bytes, &cluster_offset);
qemu_co_mutex_unlock(&s->lock);
if (ret < 0) {
return ret;
goto out;
}

if (ret == QCOW2_CLUSTER_ZERO_PLAIN ||
Expand All @@ -2106,11 +2171,14 @@ static coroutine_fn int qcow2_co_preadv_part(BlockDriverState *bs,
{
qemu_iovec_memset(qiov, qiov_offset, 0, cur_bytes);
} else {
ret = qcow2_co_preadv_task(bs, ret,
cluster_offset, offset, cur_bytes,
qiov, qiov_offset);
if (!aio && cur_bytes != bytes) {
aio = aio_task_pool_new(QCOW2_MAX_WORKERS);
}
ret = qcow2_add_task(bs, aio, qcow2_co_preadv_task_entry, ret,
cluster_offset, offset, cur_bytes,
qiov, qiov_offset, NULL);
if (ret < 0) {
return ret;
goto out;
}
}

Expand All @@ -2119,7 +2187,16 @@ static coroutine_fn int qcow2_co_preadv_part(BlockDriverState *bs,
qiov_offset += cur_bytes;
}

return 0;
out:
if (aio) {
aio_task_pool_wait_all(aio);
if (ret == 0) {
ret = aio_task_pool_status(aio);
}
g_free(aio);
}

return ret;
}

/* Check if it's possible to merge a write request with the writing of
Expand Down Expand Up @@ -2324,6 +2401,17 @@ static coroutine_fn int qcow2_co_pwritev_task(BlockDriverState *bs,
return ret;
}

static coroutine_fn int qcow2_co_pwritev_task_entry(AioTask *task)
{
Qcow2AioTask *t = container_of(task, Qcow2AioTask, task);

assert(!t->cluster_type);

return qcow2_co_pwritev_task(t->bs, t->file_cluster_offset,
t->offset, t->bytes, t->qiov, t->qiov_offset,
t->l2meta);
}

static coroutine_fn int qcow2_co_pwritev_part(
BlockDriverState *bs, uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset, int flags)
Expand All @@ -2334,10 +2422,11 @@ static coroutine_fn int qcow2_co_pwritev_part(
unsigned int cur_bytes; /* number of sectors in current iteration */
uint64_t cluster_offset;
QCowL2Meta *l2meta = NULL;
AioTaskPool *aio = NULL;

trace_qcow2_writev_start_req(qemu_coroutine_self(), offset, bytes);

while (bytes != 0) {
while (bytes != 0 && aio_task_pool_status(aio) == 0) {

l2meta = NULL;

Expand Down Expand Up @@ -2369,8 +2458,12 @@ static coroutine_fn int qcow2_co_pwritev_part(

qemu_co_mutex_unlock(&s->lock);

ret = qcow2_co_pwritev_task(bs, cluster_offset, offset, cur_bytes,
qiov, qiov_offset, l2meta);
if (!aio && cur_bytes != bytes) {
aio = aio_task_pool_new(QCOW2_MAX_WORKERS);
}
ret = qcow2_add_task(bs, aio, qcow2_co_pwritev_task_entry, 0,
cluster_offset, offset, cur_bytes,
qiov, qiov_offset, l2meta);
l2meta = NULL; /* l2meta is consumed by qcow2_co_pwritev_task() */
if (ret < 0) {
goto fail_nometa;
Expand All @@ -2391,6 +2484,14 @@ static coroutine_fn int qcow2_co_pwritev_part(
qemu_co_mutex_unlock(&s->lock);

fail_nometa:
if (aio) {
aio_task_pool_wait_all(aio);
if (ret == 0) {
ret = aio_task_pool_status(aio);
}
g_free(aio);
}

trace_qcow2_writev_done_req(qemu_coroutine_self(), ret);

return ret;
Expand Down
3 changes: 3 additions & 0 deletions block/qcow2.h
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,9 @@
#define QCOW2_MAX_BITMAPS 65535
#define QCOW2_MAX_BITMAP_DIRECTORY_SIZE (1024 * QCOW2_MAX_BITMAPS)

/* Maximum of parallel sub-request per guest request */
#define QCOW2_MAX_WORKERS 8

/* indicate that the refcount of the referenced cluster is exactly one. */
#define QCOW_OFLAG_COPIED (1ULL << 63)
/* indicate that the cluster is compressed (they never have the copied flag) */
Expand Down
1 change: 1 addition & 0 deletions block/trace-events
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,7 @@ file_paio_submit(void *acb, void *opaque, int64_t offset, int count, int type) "
file_copy_file_range(void *bs, int src, int64_t src_off, int dst, int64_t dst_off, int64_t bytes, int flags, int64_t ret) "bs %p src_fd %d offset %"PRIu64" dst_fd %d offset %"PRIu64" bytes %"PRIu64" flags %d ret %"PRId64

# qcow2.c
qcow2_add_task(void *co, void *bs, void *pool, const char *action, int cluster_type, uint64_t file_cluster_offset, uint64_t offset, uint64_t bytes, void *qiov, size_t qiov_offset) "co %p bs %p pool %p: %s: cluster_type %d file_cluster_offset %" PRIu64 " offset %" PRIu64 " bytes %" PRIu64 " qiov %p qiov_offset %zu"
qcow2_writev_start_req(void *co, int64_t offset, int bytes) "co %p offset 0x%" PRIx64 " bytes %d"
qcow2_writev_done_req(void *co, int ret) "co %p ret %d"
qcow2_writev_start_part(void *co) "co %p"
Expand Down

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