On 01.06.20 20:11, Vladimir Sementsov-Ogievskiy wrote: > We are going to directly use one async block-copy operation for backup > job, so we need rate limitator.
%s/limitator/limiter/g, I think.
> We want to maintain current backup behavior: only background copying is
> limited and copy-before-write operations only participate in limit
> calculation. Therefore we need one rate limitator for block-copy state
> and boolean flag for block-copy call state for actual limitation.
>
> Note, that we can't just calculate each chunk in limitator after
> successful copying: it will not save us from starting a lot of async
> sub-requests which will exceed limit too much. Instead let's use the
> following scheme on sub-request creation:
> 1. If at the moment limit is not exceeded, create the request and
> account it immediately.
> 2. If at the moment limit is already exceeded, drop create sub-request
> and handle limit instead (by sleep).
> With this approach we'll never exceed the limit more than by one
> sub-request (which pretty much matches current backup behavior).
Sounds reasonable.
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> ---
> include/block/block-copy.h | 8 +++++++
> block/block-copy.c | 44 ++++++++++++++++++++++++++++++++++++++
> 2 files changed, 52 insertions(+)
>
> diff --git a/include/block/block-copy.h b/include/block/block-copy.h
> index 600984c733..d40e691123 100644
> --- a/include/block/block-copy.h
> +++ b/include/block/block-copy.h
> @@ -59,6 +59,14 @@ BlockCopyCallState *block_copy_async(BlockCopyState *s,
> int64_t max_chunk,
> BlockCopyAsyncCallbackFunc cb);
>
> +/*
> + * Set speed limit for block-copy instance. All block-copy operations
> related to
> + * this BlockCopyState will participate in speed calculation, but only
> + * block_copy_async calls with @ratelimit=true will be actually limited.
> + */
> +void block_copy_set_speed(BlockCopyState *s, BlockCopyCallState *call_state,
> + uint64_t speed);
> +
> BdrvDirtyBitmap *block_copy_dirty_bitmap(BlockCopyState *s);
> void block_copy_set_skip_unallocated(BlockCopyState *s, bool skip);
>
> diff --git a/block/block-copy.c b/block/block-copy.c
> index 4114d1fd25..851d9c8aaf 100644
> --- a/block/block-copy.c
> +++ b/block/block-copy.c
> @@ -26,6 +26,7 @@
> #define BLOCK_COPY_MAX_BUFFER (1 * MiB)
> #define BLOCK_COPY_MAX_MEM (128 * MiB)
> #define BLOCK_COPY_MAX_WORKERS 64
> +#define BLOCK_COPY_SLICE_TIME 100000000ULL /* ns */
>
> static coroutine_fn int block_copy_task_entry(AioTask *task);
>
> @@ -36,11 +37,13 @@ typedef struct BlockCopyCallState {
> int64_t bytes;
> int max_workers;
> int64_t max_chunk;
> + bool ratelimit;
> BlockCopyAsyncCallbackFunc cb;
>
> /* State */
> bool failed;
> bool finished;
> + QemuCoSleepState *sleep_state;
>
> /* OUT parameters */
> bool error_is_read;
> @@ -103,6 +106,9 @@ typedef struct BlockCopyState {
> void *progress_opaque;
>
> SharedResource *mem;
> +
> + uint64_t speed;
> + RateLimit rate_limit;
> } BlockCopyState;
>
> static BlockCopyTask *find_conflicting_task(BlockCopyState *s,
> @@ -611,6 +617,21 @@ block_copy_dirty_clusters(BlockCopyCallState *call_state)
> }
> task->zeroes = ret & BDRV_BLOCK_ZERO;
>
> + if (s->speed) {
> + if (call_state->ratelimit) {
> + uint64_t ns = ratelimit_calculate_delay(&s->rate_limit, 0);
> + if (ns > 0) {
> + block_copy_task_end(task, -EAGAIN);
> + g_free(task);
> + qemu_co_sleep_ns_wakeable(QEMU_CLOCK_REALTIME, ns,
> + &call_state->sleep_state);
> + continue;
> + }
> + }
> +
> + ratelimit_calculate_delay(&s->rate_limit, task->bytes);
> + }
> +
Looks good.
> trace_block_copy_process(s, task->offset);
>
> co_get_from_shres(s->mem, task->bytes);
> @@ -649,6 +670,13 @@ out:
> return ret < 0 ? ret : found_dirty;
> }
>
> +static void block_copy_kick(BlockCopyCallState *call_state)
> +{
> + if (call_state->sleep_state) {
> + qemu_co_sleep_wake(call_state->sleep_state);
> + }
> +}
> +
> /*
> * block_copy_common
> *
> @@ -729,6 +757,7 @@ BlockCopyCallState *block_copy_async(BlockCopyState *s,
> .s = s,
> .offset = offset,
> .bytes = bytes,
> + .ratelimit = ratelimit,
Hm, same problem/question as in patch 6: Should the @ratelimit parameter
really be added in patch 5 if it’s used only now?
> .cb = cb,
> .max_workers = max_workers ?: BLOCK_COPY_MAX_WORKERS,
> .max_chunk = max_chunk,
> @@ -752,3 +781,18 @@ void block_copy_set_skip_unallocated(BlockCopyState *s,
> bool skip)
> {
> s->skip_unallocated = skip;
> }
> +
> +void block_copy_set_speed(BlockCopyState *s, BlockCopyCallState *call_state,
> + uint64_t speed)
> +{
> + uint64_t old_speed = s->speed;
> +
> + s->speed = speed;
> + if (speed > 0) {
> + ratelimit_set_speed(&s->rate_limit, speed, BLOCK_COPY_SLICE_TIME);
> + }
> +
> + if (call_state && old_speed && (speed > old_speed || speed == 0)) {
> + block_copy_kick(call_state);
> + }
> +}
Hm. I’m interested in seeing how this is going to be used, i.e. what
callers will pass for @call_state. I suppose it’s going to be the
background operation for the whole device, but I wonder whether it
actually makes sense to pass it. I mean, the caller could just call
block_copy_kick() itself (unconditionally, because it’ll never hurt, I
think).
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