diff mbox series

[v3,8/9] block/block-copy: reduce intersecting request lock

Message ID 20200306073831.7737-9-vsementsov@virtuozzo.com
State New
Headers show
Series block-copy improvements: part I | expand

Commit Message

Vladimir Sementsov-Ogievskiy March 6, 2020, 7:38 a.m. UTC 
Currently, block_copy operation lock the whole requested region. But
there is no reason to lock clusters, which are already copied, it will
disturb other parallel block_copy requests for no reason.

Let's instead do the following:

Lock only sub-region, which we are going to operate on. Then, after
copying all dirty sub-regions, we should wait for intersecting
requests block-copy, if they failed, we should retry these new dirty
clusters.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 block/block-copy.c | 128 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 104 insertions(+), 24 deletions(-)

Comments

Max Reitz March 10, 2020, 3:32 p.m. UTC | #1 
On 06.03.20 08:38, Vladimir Sementsov-Ogievskiy wrote:
> Currently, block_copy operation lock the whole requested region. But
> there is no reason to lock clusters, which are already copied, it will
> disturb other parallel block_copy requests for no reason.
> 
> Let's instead do the following:
> 
> Lock only sub-region, which we are going to operate on. Then, after
> copying all dirty sub-regions, we should wait for intersecting
> requests block-copy, if they failed, we should retry these new dirty
> clusters.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>  block/block-copy.c | 128 ++++++++++++++++++++++++++++++++++++---------
>  1 file changed, 104 insertions(+), 24 deletions(-)
> 
> diff --git a/block/block-copy.c b/block/block-copy.c
> index 2b29131653..d66b8eb691 100644
> --- a/block/block-copy.c
> +++ b/block/block-copy.c

[...]

> +/* Called only on full-dirty region */
>  static void block_copy_inflight_req_begin(BlockCopyState *s,
>                                            BlockCopyInFlightReq *req,
>                                            int64_t offset, int64_t bytes)
>  {
> +    assert(!find_conflicting_inflight_req(s, offset, bytes));
> +
> +    bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
> +    s->in_flight_bytes += bytes;
> +
>      req->offset = offset;
>      req->bytes = bytes;
>      qemu_co_queue_init(&req->wait_queue);
>      QLIST_INSERT_HEAD(&s->inflight_reqs, req, list);
>  }
>  
> -static void coroutine_fn block_copy_inflight_req_end(BlockCopyInFlightReq *req)
> +/*
> + * block_copy_inflight_req_shrink
> + *
> + * Drop the tail of the request to be handled later. Set dirty bits back and
> + * wake up all requests waiting for us (may be some of them are not intersecting
> + * with shrunk request)
> + */
> +static void coroutine_fn block_copy_inflight_req_shrink(BlockCopyState *s,
> +        BlockCopyInFlightReq *req, int64_t new_bytes)
>  {
> +    if (new_bytes == req->bytes) {
> +        return;
> +    }
> +
> +    assert(new_bytes > 0 && new_bytes < req->bytes);
> +
> +    bdrv_set_dirty_bitmap(s->copy_bitmap,
> +                          req->offset + new_bytes, req->bytes - new_bytes);

I think we need to reduce in_flight_bytes here.

> +
> +    req->bytes = new_bytes;
> +    qemu_co_queue_restart_all(&req->wait_queue);
> +}
> +
> +static void coroutine_fn block_copy_inflight_req_end(BlockCopyState *s,
> +                                                     BlockCopyInFlightReq *req,
> +                                                     int ret)
> +{
> +    s->in_flight_bytes -= req->bytes;
> +    if (ret < 0) {
> +        bdrv_set_dirty_bitmap(s->copy_bitmap, req->offset, req->bytes);
> +    }
>      QLIST_REMOVE(req, list);
>      qemu_co_queue_restart_all(&req->wait_queue);
>  }

[...]

> @@ -432,7 +479,40 @@ int coroutine_fn block_copy(BlockCopyState *s,
>          bytes -= cur_bytes;
>      }
>  
> -    block_copy_inflight_req_end(&req);
> +    return found_dirty;
> +}
> +
> +/*
> + * block_copy
> + *
> + * Copy requested region, accordingly to dirty bitmap.
> + * Collaborate with parallel block_copy requests: if they success it help us. If

s/success/succeed/, s/it help/it will help/

> + * they fail, we retry not-copied regions. So, if we return error, it means that

s/retry/will retry/

(In theory also s/it means/it will mean/, but I suppose that also works
as-is.)

> + * io operation failed in context of _this_ block_copy call, not some parallel

Perhaps rather “some I/O operation failed in the context of […]”?

> + * operation.
> + */
> +int coroutine_fn block_copy(BlockCopyState *s, int64_t offset, int64_t bytes,
> +                            bool *error_is_read)
> +{
> +    int ret;
> +
> +    do {
> +        ret = block_copy_dirty_clusters(s, offset, bytes, error_is_read);
> +
> +        if (ret == 0) {
> +            ret = block_copy_wait_one(s, offset, bytes);
> +        }
> +
> +        /*
> +         * We retry in two cases:
> +         * 1. Some progress done
> +         *    Something was copied, which means that there were yield points
> +         *    and some new dirty bits may have appeared (due to failed parallel
> +         *    block-copy requests).
> +         * 2. We have waited for some intersecting block-copy request
> +         *    It may have failed and produced new dirty bits.
> +         */
> +    } while (ret > 0);
>  
>      return ret;
>  }

This new code looks good.

Max
Vladimir Sementsov-Ogievskiy March 11, 2020, 9:39 a.m. UTC | #2 
10.03.2020 18:32, Max Reitz wrote:
> On 06.03.20 08:38, Vladimir Sementsov-Ogievskiy wrote:
>> Currently, block_copy operation lock the whole requested region. But
>> there is no reason to lock clusters, which are already copied, it will
>> disturb other parallel block_copy requests for no reason.
>>
>> Let's instead do the following:
>>
>> Lock only sub-region, which we are going to operate on. Then, after
>> copying all dirty sub-regions, we should wait for intersecting
>> requests block-copy, if they failed, we should retry these new dirty
>> clusters.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
>> ---
>>   block/block-copy.c | 128 ++++++++++++++++++++++++++++++++++++---------
>>   1 file changed, 104 insertions(+), 24 deletions(-)
>>
>> diff --git a/block/block-copy.c b/block/block-copy.c
>> index 2b29131653..d66b8eb691 100644
>> --- a/block/block-copy.c
>> +++ b/block/block-copy.c
> 
> [...]
> 
>> +/* Called only on full-dirty region */
>>   static void block_copy_inflight_req_begin(BlockCopyState *s,
>>                                             BlockCopyInFlightReq *req,
>>                                             int64_t offset, int64_t bytes)
>>   {
>> +    assert(!find_conflicting_inflight_req(s, offset, bytes));
>> +
>> +    bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
>> +    s->in_flight_bytes += bytes;
>> +
>>       req->offset = offset;
>>       req->bytes = bytes;
>>       qemu_co_queue_init(&req->wait_queue);
>>       QLIST_INSERT_HEAD(&s->inflight_reqs, req, list);
>>   }
>>   
>> -static void coroutine_fn block_copy_inflight_req_end(BlockCopyInFlightReq *req)
>> +/*
>> + * block_copy_inflight_req_shrink
>> + *
>> + * Drop the tail of the request to be handled later. Set dirty bits back and
>> + * wake up all requests waiting for us (may be some of them are not intersecting
>> + * with shrunk request)
>> + */
>> +static void coroutine_fn block_copy_inflight_req_shrink(BlockCopyState *s,
>> +        BlockCopyInFlightReq *req, int64_t new_bytes)
>>   {
>> +    if (new_bytes == req->bytes) {
>> +        return;
>> +    }
>> +
>> +    assert(new_bytes > 0 && new_bytes < req->bytes);
>> +
>> +    bdrv_set_dirty_bitmap(s->copy_bitmap,
>> +                          req->offset + new_bytes, req->bytes - new_bytes);
> 
> I think we need to reduce in_flight_bytes here.

Yes, you are right, thanks!

> 
>> +
>> +    req->bytes = new_bytes;
>> +    qemu_co_queue_restart_all(&req->wait_queue);
>> +}
>> +
>> +static void coroutine_fn block_copy_inflight_req_end(BlockCopyState *s,
>> +                                                     BlockCopyInFlightReq *req,
>> +                                                     int ret)
>> +{
>> +    s->in_flight_bytes -= req->bytes;
>> +    if (ret < 0) {
>> +        bdrv_set_dirty_bitmap(s->copy_bitmap, req->offset, req->bytes);
>> +    }
>>       QLIST_REMOVE(req, list);
>>       qemu_co_queue_restart_all(&req->wait_queue);
>>   }
> 
> [...]
> 
>> @@ -432,7 +479,40 @@ int coroutine_fn block_copy(BlockCopyState *s,
>>           bytes -= cur_bytes;
>>       }
>>   
>> -    block_copy_inflight_req_end(&req);
>> +    return found_dirty;
>> +}
>> +
>> +/*
>> + * block_copy
>> + *
>> + * Copy requested region, accordingly to dirty bitmap.
>> + * Collaborate with parallel block_copy requests: if they success it help us. If
> 
> s/success/succeed/, s/it help/it will help/
> 
>> + * they fail, we retry not-copied regions. So, if we return error, it means that
> 
> s/retry/will retry/
> 
> (In theory also s/it means/it will mean/, but I suppose that also works
> as-is.)
> 
>> + * io operation failed in context of _this_ block_copy call, not some parallel
> 
> Perhaps rather “some I/O operation failed in the context of […]”?
> 
>> + * operation.
>> + */
>> +int coroutine_fn block_copy(BlockCopyState *s, int64_t offset, int64_t bytes,
>> +                            bool *error_is_read)
>> +{
>> +    int ret;
>> +
>> +    do {
>> +        ret = block_copy_dirty_clusters(s, offset, bytes, error_is_read);
>> +
>> +        if (ret == 0) {
>> +            ret = block_copy_wait_one(s, offset, bytes);
>> +        }
>> +
>> +        /*
>> +         * We retry in two cases:
>> +         * 1. Some progress done
>> +         *    Something was copied, which means that there were yield points
>> +         *    and some new dirty bits may have appeared (due to failed parallel
>> +         *    block-copy requests).
>> +         * 2. We have waited for some intersecting block-copy request
>> +         *    It may have failed and produced new dirty bits.
>> +         */
>> +    } while (ret > 0);
>>   
>>       return ret;
>>   }
> 
> This new code looks good.
> 
> Max
>
diff mbox series

Patch

diff --git a/block/block-copy.c b/block/block-copy.c
index 2b29131653..d66b8eb691 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -39,29 +39,71 @@  static BlockCopyInFlightReq *find_conflicting_inflight_req(BlockCopyState *s,
     return NULL;
 }
 
-static void coroutine_fn block_copy_wait_inflight_reqs(BlockCopyState *s,
-                                                       int64_t offset,
-                                                       int64_t bytes)
+/*
+ * If there are no intersecting requests return false. Otherwise, wait for the
+ * first found intersecting request to finish and return true.
+ */
+static bool coroutine_fn block_copy_wait_one(BlockCopyState *s, int64_t offset,
+                                             int64_t bytes)
 {
-    BlockCopyInFlightReq *req;
+    BlockCopyInFlightReq *req = find_conflicting_inflight_req(s, offset, bytes);
 
-    while ((req = find_conflicting_inflight_req(s, offset, bytes))) {
-        qemu_co_queue_wait(&req->wait_queue, NULL);
+    if (!req) {
+        return false;
     }
+
+    qemu_co_queue_wait(&req->wait_queue, NULL);
+
+    return true;
 }
 
+/* Called only on full-dirty region */
 static void block_copy_inflight_req_begin(BlockCopyState *s,
                                           BlockCopyInFlightReq *req,
                                           int64_t offset, int64_t bytes)
 {
+    assert(!find_conflicting_inflight_req(s, offset, bytes));
+
+    bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
+    s->in_flight_bytes += bytes;
+
     req->offset = offset;
     req->bytes = bytes;
     qemu_co_queue_init(&req->wait_queue);
     QLIST_INSERT_HEAD(&s->inflight_reqs, req, list);
 }
 
-static void coroutine_fn block_copy_inflight_req_end(BlockCopyInFlightReq *req)
+/*
+ * block_copy_inflight_req_shrink
+ *
+ * Drop the tail of the request to be handled later. Set dirty bits back and
+ * wake up all requests waiting for us (may be some of them are not intersecting
+ * with shrunk request)
+ */
+static void coroutine_fn block_copy_inflight_req_shrink(BlockCopyState *s,
+        BlockCopyInFlightReq *req, int64_t new_bytes)
 {
+    if (new_bytes == req->bytes) {
+        return;
+    }
+
+    assert(new_bytes > 0 && new_bytes < req->bytes);
+
+    bdrv_set_dirty_bitmap(s->copy_bitmap,
+                          req->offset + new_bytes, req->bytes - new_bytes);
+
+    req->bytes = new_bytes;
+    qemu_co_queue_restart_all(&req->wait_queue);
+}
+
+static void coroutine_fn block_copy_inflight_req_end(BlockCopyState *s,
+                                                     BlockCopyInFlightReq *req,
+                                                     int ret)
+{
+    s->in_flight_bytes -= req->bytes;
+    if (ret < 0) {
+        bdrv_set_dirty_bitmap(s->copy_bitmap, req->offset, req->bytes);
+    }
     QLIST_REMOVE(req, list);
     qemu_co_queue_restart_all(&req->wait_queue);
 }
@@ -357,12 +399,19 @@  int64_t block_copy_reset_unallocated(BlockCopyState *s,
     return ret;
 }
 
-int coroutine_fn block_copy(BlockCopyState *s,
-                            int64_t offset, int64_t bytes,
-                            bool *error_is_read)
+/*
+ * block_copy_dirty_clusters
+ *
+ * Copy dirty clusters in @offset/@bytes range.
+ * Returns 1 if dirty clusters found and successfully copied, 0 if no dirty
+ * clusters found and -errno on failure.
+ */
+static int coroutine_fn block_copy_dirty_clusters(BlockCopyState *s,
+                                                  int64_t offset, int64_t bytes,
+                                                  bool *error_is_read)
 {
     int ret = 0;
-    BlockCopyInFlightReq req;
+    bool found_dirty = false;
 
     /*
      * block_copy() user is responsible for keeping source and target in same
@@ -374,10 +423,8 @@  int coroutine_fn block_copy(BlockCopyState *s,
     assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
     assert(QEMU_IS_ALIGNED(bytes, s->cluster_size));
 
-    block_copy_wait_inflight_reqs(s, offset, bytes);
-    block_copy_inflight_req_begin(s, &req, offset, bytes);
-
     while (bytes) {
+        BlockCopyInFlightReq req;
         int64_t next_zero, cur_bytes, status_bytes;
 
         if (!bdrv_dirty_bitmap_get(s->copy_bitmap, offset)) {
@@ -387,6 +434,8 @@  int coroutine_fn block_copy(BlockCopyState *s,
             continue; /* already copied */
         }
 
+        found_dirty = true;
+
         cur_bytes = MIN(bytes, s->copy_size);
 
         next_zero = bdrv_dirty_bitmap_next_zero(s->copy_bitmap, offset,
@@ -396,10 +445,14 @@  int coroutine_fn block_copy(BlockCopyState *s,
             assert(next_zero < offset + cur_bytes); /* no need to do MIN() */
             cur_bytes = next_zero - offset;
         }
+        block_copy_inflight_req_begin(s, &req, offset, cur_bytes);
 
         ret = block_copy_block_status(s, offset, cur_bytes, &status_bytes);
+        assert(ret >= 0); /* never fail */
+        cur_bytes = MIN(cur_bytes, status_bytes);
+        block_copy_inflight_req_shrink(s, &req, cur_bytes);
         if (s->skip_unallocated && !(ret & BDRV_BLOCK_ALLOCATED)) {
-            bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, status_bytes);
+            block_copy_inflight_req_end(s, &req, 0);
             progress_set_remaining(s->progress,
                                    bdrv_get_dirty_count(s->copy_bitmap) +
                                    s->in_flight_bytes);
@@ -409,21 +462,15 @@  int coroutine_fn block_copy(BlockCopyState *s,
             continue;
         }
 
-        cur_bytes = MIN(cur_bytes, status_bytes);
-
         trace_block_copy_process(s, offset);
 
-        bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, cur_bytes);
-        s->in_flight_bytes += cur_bytes;
-
         co_get_from_shres(s->mem, cur_bytes);
         ret = block_copy_do_copy(s, offset, cur_bytes, ret & BDRV_BLOCK_ZERO,
                                  error_is_read);
         co_put_to_shres(s->mem, cur_bytes);
-        s->in_flight_bytes -= cur_bytes;
+        block_copy_inflight_req_end(s, &req, ret);
         if (ret < 0) {
-            bdrv_set_dirty_bitmap(s->copy_bitmap, offset, cur_bytes);
-            break;
+            return ret;
         }
 
         progress_work_done(s->progress, cur_bytes);
@@ -432,7 +479,40 @@  int coroutine_fn block_copy(BlockCopyState *s,
         bytes -= cur_bytes;
     }
 
-    block_copy_inflight_req_end(&req);
+    return found_dirty;
+}
+
+/*
+ * block_copy
+ *
+ * Copy requested region, accordingly to dirty bitmap.
+ * Collaborate with parallel block_copy requests: if they success it help us. If
+ * they fail, we retry not-copied regions. So, if we return error, it means that
+ * io operation failed in context of _this_ block_copy call, not some parallel
+ * operation.
+ */
+int coroutine_fn block_copy(BlockCopyState *s, int64_t offset, int64_t bytes,
+                            bool *error_is_read)
+{
+    int ret;
+
+    do {
+        ret = block_copy_dirty_clusters(s, offset, bytes, error_is_read);
+
+        if (ret == 0) {
+            ret = block_copy_wait_one(s, offset, bytes);
+        }
+
+        /*
+         * We retry in two cases:
+         * 1. Some progress done
+         *    Something was copied, which means that there were yield points
+         *    and some new dirty bits may have appeared (due to failed parallel
+         *    block-copy requests).
+         * 2. We have waited for some intersecting block-copy request
+         *    It may have failed and produced new dirty bits.
+         */
+    } while (ret > 0);
 
     return ret;
 }