Re: [PATCH v2 07/12] qapi/block: Add BLOCK_IO_DONE event

[Hanna Czenczek]

On 20.10.26 08:55, Markus Armbruster wrote:

Hanna Czenczek <hre...@redhat.com> writes:

This event is emitted when an operation completes, for which a
BLOCK_IO_DELAY event has previously been emitted.

Signed-off-by: Hanna Czenczek <hre...@redhat.com>
---
  qapi/block.json | 33 +++++++++++++++++++++++++++++++++
  1 file changed, 33 insertions(+)

diff --git a/qapi/block.json b/qapi/block.json
index 5f9f5c28050..38f293dd32d 100644
--- a/qapi/block.json
+++ b/qapi/block.json
@@ -660,6 +660,9 @@
  # Note that delays deliberately incurred by throttling do count
  # towards the operation duration.
  #
+# This event will only be emitted once per request and action.  When
+# the operation does finish, a `BLOCK_IO_DONE` event is emitted.

I think the first sentence answers a question I had on the previous
patch.  Move it there?

Sure.

+#
  # @qom-path: path to the block device object in the QOM tree
  #
  # @operation: I/O operation
@@ -686,3 +689,33 @@
        'action': 'BlockErrorAction',
        '*offset': 'uint64',
        'bytes': 'uint64' } }
+
+##
+# @BLOCK_IO_DONE:
+#
+# Emitted on completion for disk operations that previously emitted a
+# `BLOCK_IO_DELAY` event.

Can we have multiple operations in flight that previously emitted
BLOCK_IO_DELAY?

If yes, might a management application need to connect the BLOCK_IO_DONE
back to the BLOCK_IO_DELAY?

If yes, how could it do that?

Well, the combination of device, operation, offset, bytes.

Do you think there should be an ID like a u64 counter per BlockBackend?

Please use the revised syntax for introductions:

    ##
    # @BLOCK_IO_DONE: Emitted on completion for disk operations that
    #     previously emitted a `BLOCK_IO_DELAY` event.

Sure.

+#
+# @qom-path: path to the block device object in the QOM tree
+#
+# @operation: I/O operation
+#
+# @latency-ns: Full duration of the operation (in nanoseconds)
+#
+# @offset: Request offset in the guest disk (in bytes), if available

Out of curiosity: when could @offset be unavailable?

For flushes.

+#
+# @bytes: Request length
+#
+# @failed: If true, this request failed for any reason.  If false, the

Suggest "for some reason".

Sure!

Hanna

+#     request succeeded.
+#
+# Since: 11.2
+##
+{ 'event': 'BLOCK_IO_DONE',
+  'data': {
+      'qom-path': 'str',
+      'operation': 'IoAccountingOperation',
+      'latency-ns': 'uint64',
+      '*offset': 'uint64',
+      'bytes': 'uint64',
+      'failed': 'bool' } }