aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorStefan Hajnoczi <stefanha@linux.vnet.ibm.com>2012-01-18 14:40:45 +0000
committerKevin Wolf <kwolf@redhat.com>2012-01-26 11:45:26 +0100
commit5094a6c016f6e7a4fc800816d716e10ce2331396 (patch)
tree5e4bf84bc906e65691479f910e3bdb3a71bd0a45
parent4f1043b4ffdd6f130cab7c1d8d59d833a475adac (diff)
downloadqemu-5094a6c016f6e7a4fc800816d716e10ce2331396.zip
qemu-5094a6c016f6e7a4fc800816d716e10ce2331396.tar.gz
qemu-5094a6c016f6e7a4fc800816d716e10ce2331396.tar.bz2
block: rate-limit streaming operations
This patch implements rate-limiting for image streaming. If we've exceeded the bandwidth quota for a 100 ms time slice we sleep the coroutine until the next slice begins. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block/stream.c65
1 files changed, 59 insertions, 6 deletions
diff --git a/block/stream.c b/block/stream.c
index 3a99094..b54b0b7 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -23,8 +23,39 @@ enum {
STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
};
+#define SLICE_TIME 100000000ULL /* ns */
+
+typedef struct {
+ int64_t next_slice_time;
+ uint64_t slice_quota;
+ uint64_t dispatched;
+} RateLimit;
+
+static int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
+{
+ int64_t delay_ns = 0;
+ int64_t now = qemu_get_clock_ns(rt_clock);
+
+ if (limit->next_slice_time < now) {
+ limit->next_slice_time = now + SLICE_TIME;
+ limit->dispatched = 0;
+ }
+ if (limit->dispatched + n > limit->slice_quota) {
+ delay_ns = limit->next_slice_time - now;
+ } else {
+ limit->dispatched += n;
+ }
+ return delay_ns;
+}
+
+static void ratelimit_set_speed(RateLimit *limit, uint64_t speed)
+{
+ limit->slice_quota = speed / (1000000000ULL / SLICE_TIME);
+}
+
typedef struct StreamBlockJob {
BlockJob common;
+ RateLimit limit;
BlockDriverState *base;
} StreamBlockJob;
@@ -72,20 +103,24 @@ static void coroutine_fn stream_run(void *opaque)
}
for (sector_num = 0; sector_num < end; sector_num += n) {
+retry:
if (block_job_is_cancelled(&s->common)) {
break;
}
- /* TODO rate-limit */
- /* Note that even when no rate limit is applied we need to yield with
- * no pending I/O here so that qemu_aio_flush() is able to return.
- */
- co_sleep_ns(rt_clock, 0);
-
ret = bdrv_co_is_allocated(bs, sector_num,
STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
trace_stream_one_iteration(s, sector_num, n, ret);
if (ret == 0) {
+ if (s->common.speed) {
+ uint64_t delay_ns = ratelimit_calculate_delay(&s->limit, n);
+ if (delay_ns > 0) {
+ co_sleep_ns(rt_clock, delay_ns);
+
+ /* Recheck cancellation and that sectors are unallocated */
+ goto retry;
+ }
+ }
ret = stream_populate(bs, sector_num, n, buf);
}
if (ret < 0) {
@@ -94,6 +129,11 @@ static void coroutine_fn stream_run(void *opaque)
/* Publish progress */
s->common.offset += n * BDRV_SECTOR_SIZE;
+
+ /* Note that even when no rate limit is applied we need to yield
+ * with no pending I/O here so that qemu_aio_flush() returns.
+ */
+ co_sleep_ns(rt_clock, 0);
}
if (!base) {
@@ -108,9 +148,22 @@ static void coroutine_fn stream_run(void *opaque)
block_job_complete(&s->common, ret);
}
+static int stream_set_speed(BlockJob *job, int64_t value)
+{
+ StreamBlockJob *s = container_of(job, StreamBlockJob, common);
+
+ if (value < 0) {
+ return -EINVAL;
+ }
+ job->speed = value;
+ ratelimit_set_speed(&s->limit, value / BDRV_SECTOR_SIZE);
+ return 0;
+}
+
static BlockJobType stream_job_type = {
.instance_size = sizeof(StreamBlockJob),
.job_type = "stream",
+ .set_speed = stream_set_speed,
};
int stream_start(BlockDriverState *bs, BlockDriverState *base,