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Re: [Qemu-devel] [PATCH v5 14/38] block: Remove wr_highest_sector from B
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v5 14/38] block: Remove wr_highest_sector from BlockAcctStats |
Date: |
Fri, 18 Sep 2015 10:59:14 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 |
On 09/18/2015 09:22 AM, Max Reitz wrote:
> BlockAcctStats contains statistics about the data transferred from and
> to the device; wr_highest_sector does not fit in with the rest.
>
> Furthermore, those statistics are supposed to be specific for a certain
> device and not necessarily for a BDS (see the comment above
> bdrv_get_stats()); on the other hand, wr_highest_sector may be a rather
> important information to know for each BDS. When BlockAcctStats is
> finally removed from the BDS, we will want to keep wr_highest_sector in
> the BDS.
>
> Finally, wr_highest_sector is renamed to wr_highest_offset and given the
> appropriate meaning. Externally, it is represented as an offset so there
> is no point in doing something different internally. Its definition is
> changed to match that in qapi/block-core.json which is "the offset after
> the greatest byte written to". Doing so should not cause any harm since
> if external programs tried to calculate the volume usage by
> (wr_highest_offset + 512) / volume_size, after this patch they will just
> assume the volume to be full slightly earlier than before.
>
> Signed-off-by: Max Reitz <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>
> Reviewed-by: Alberto Garcia <address@hidden>
Still holds, but...
> +++ b/qmp-commands.hx
> @@ -2481,8 +2481,8 @@ Each json-object contain the following:
> - "wr_total_time_ns": total time spend on writes in nano-seconds
> (json-int)
> - "rd_total_time_ns": total time spend on reads in nano-seconds
> (json-int)
> - "flush_total_time_ns": total time spend on cache flushes in
> nano-seconds (json-int)
> - - "wr_highest_offset": Highest offset of a sector written since the
> - BlockDriverState has been opened (json-int)
> + - "wr_highest_offset": The offset after the greatest byte written to the
> + BlockDriverState since it has been opened
> (json-int)
...someday, I'd really like to have this stat show as non-zero even when
first opening the device (before writing to it). Right now, you have no
clue how full a backing device is prior to starting a block-commit; you
have to start writing to it to get a feel for its current usage.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH v5 08/38] block/raw_bsd: Drop raw_is_inserted(), (continued)
- [Qemu-devel] [PATCH v5 08/38] block/raw_bsd: Drop raw_is_inserted(), Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 10/38] hw/block/fdc: Implement tray status, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 09/38] block: Invoke change media CB before NULLing drv, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 11/38] hw/usb-storage: Check whether BB is inserted, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 13/38] block: Move guest_block_size into BlockBackend, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 12/38] block: Fix BB AIOCB AioContext without BDS, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 14/38] block: Remove wr_highest_sector from BlockAcctStats, Max Reitz, 2015/09/18
- Re: [Qemu-devel] [PATCH v5 14/38] block: Remove wr_highest_sector from BlockAcctStats,
Eric Blake <=
- [Qemu-devel] [PATCH v5 15/38] block: Move BlockAcctStats into BlockBackend, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 16/38] block: Move I/O status and error actions into BB, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 17/38] block: Add BlockBackendRootState, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 18/38] block: Make some BB functions fall back to BBRS, Max Reitz, 2015/09/18
- [Qemu-devel] [PATCH v5 19/38] block: Fail requests to empty BlockBackend, Max Reitz, 2015/09/18