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Re: [Qemu-devel] [PATCH v4 0/8] discard blockstats
From: |
Anton Nefedov |
Subject: |
Re: [Qemu-devel] [PATCH v4 0/8] discard blockstats |
Date: |
Thu, 4 Oct 2018 14:04:45 +0000 |
ping-2
On 18/9/2018 11:12 AM, Anton Nefedov wrote:
> ping
>
> do you think we might proceed with this? or is there any general doubt
> about the idea?
>
> thanks,
>
> On 21/8/2018 12:46 PM, Anton Nefedov wrote:
>> new in v4:
>> - patch 7: discard and write-zeroes code paths had been separated in
>> 34fa110e: file-posix: Fix write_zeroes with unmap on block
>> devices.
>> This patch now only accounts discards that come explicitly
>> through .bdrv_co_pdiscard handler.
>> - qapi 'Since' clauses changed 3.0 -> 3.1
>>
>> v3: http://lists.nongnu.org/archive/html/qemu-devel/2018-06/msg03688.html
>>
>> ----
>>
>> qmp query-blockstats provides stats info for write/read/flush ops.
>>
>> Patches 1-6 implement the similar for discard (unmap) command for scsi
>> and ide disks.
>> Discard stat "unmap_ops / unmap_bytes" is supposed to account the ops
>> that
>> have completed without an error.
>>
>> However, discard operation is advisory. Specifically,
>> - common block layer ignores ENOTSUP error code.
>> That might be returned if the block driver does not support discard,
>> or discard has been configured to be ignored.
>> - format drivers such as qcow2 may ignore discard if they were
>> configured
>> to ignore that, or if the corresponding area is already marked unused
>> (unallocated / zero clusters).
>>
>> And what is actually useful is the number of bytes actually discarded
>> down on the host filesystem.
>> To achieve that, driver-specific statistics has been added to blockstats
>> (patch 8).
>> With patch 7, file-posix driver accounts discard operations on its
>> level too.
>>
>> query-blockstat result:
>>
>> (note the difference between blockdevice unmap and file discard stats.
>> qcow2
>> sends fewer ops down to the file as the clusters are actually unallocated
>> on qcow2 level)
>>
>> {
>> "return": [
>> {
>> "device": "drive-scsi0-0-0-0",
>> "parent": {
>>> "discard-bytes-ok": 262144,
>>> "discard-nb-ok": 4,
>> "stats": {
>>> "unmap_operations": 0,
>>> "unmap_merged": 0,
>> "flush_total_time_ns": 0,
>> "wr_highest_offset": 8111718400,
>> "wr_total_time_ns": 0,
>> "failed_wr_operations": 0,
>> "failed_rd_operations": 0,
>> "wr_merged": 0,
>> "wr_bytes": 0,
>> "timed_stats": [
>> ],
>>> "failed_unmap_operations": 0,
>> "failed_flush_operations": 0,
>> "account_invalid": false,
>> "rd_total_time_ns": 0,
>>> "invalid_unmap_operations": 0,
>> "flush_operations": 0,
>> "wr_operations": 0,
>>> "unmap_bytes": 0,
>> "rd_merged": 0,
>> "rd_bytes": 0,
>>> "unmap_total_time_ns": 0,
>> "invalid_flush_operations": 0,
>> "account_failed": false,
>> "rd_operations": 0,
>> "invalid_wr_operations": 0,
>> "invalid_rd_operations": 0
>> },
>> "node-name": "#block012",
>>> "driver": "file",
>>> "discard-nb-failed": 0
>> },
>> "stats": {
>>> "unmap_operations": 860,
>>> "unmap_merged": 0,
>> "flush_total_time_ns": 21506733,
>> "wr_highest_offset": 13411741696,
>> "wr_total_time_ns": 2212749334,
>> "failed_wr_operations": 0,
>> "failed_rd_operations": 0,
>> "wr_merged": 0,
>> "wr_bytes": 3426304,
>> "timed_stats": [
>> ],
>>> "failed_unmap_operations": 0,
>> "failed_flush_operations": 0,
>> "account_invalid": true,
>> "rd_total_time_ns": 3617478206,
>>> "invalid_unmap_operations": 0,
>> "flush_operations": 24,
>> "wr_operations": 309,
>>> "unmap_bytes": 11949633536,
>> "rd_merged": 0,
>> "rd_bytes": 141967360,
>>> "unmap_total_time_ns": 14871816,
>> [..]
>>
>> Anton Nefedov (8):
>> qapi: group BlockDeviceStats fields
>> qapi: add unmap to BlockDeviceStats
>> ide: account UNMAP (TRIM) operations
>> scsi: store unmap offset and nb_sectors in request struct
>> scsi: move unmap error checking to the complete callback
>> scsi: account unmap operations
>> file-posix: account discard operations
>> qapi: query-blockstat: add driver specific file-posix stats
>>
>> qapi/block-core.json | 82
>> +++++++++++++++++++++++++++++++++++++++-------
>> include/block/accounting.h | 1 +
>> include/block/block.h | 1 +
>> include/block/block_int.h | 1 +
>> block.c | 9 +++++
>> block/file-posix.c | 45 +++++++++++++++++++++++--
>> block/qapi.c | 11 +++++++
>> hw/ide/core.c | 12 +++++++
>> hw/scsi/scsi-disk.c | 29 +++++++++-------
>> tests/qemu-iotests/227.out | 18 ++++++++++
>> 10 files changed, 184 insertions(+), 25 deletions(-)
>>
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