Re: [RFC 0/3] block/file-posix: Work around XFS bug

[Max Reitz]

On 04.11.19 16:49, Alberto Garcia wrote:
> On Mon 04 Nov 2019 04:14:56 PM CET, Max Reitz wrote:
> 
>>>> No, what I meant was that the original problem that led to
>>>> c8bb23cbdbe would go away.
>>>
>>> Ah, right. Not quite, according to my numbers:
>>>
>>> |--------------+----------------+-----------------+-------------|
>>> | Cluster size | subclusters=on | subclusters=off | fallocate() |
>>> |--------------+----------------+-----------------+-------------|
>>> |       256 KB |     10182 IOPS |        966 IOPS |  14007 IOPS |
>>> |       512 KB |      7919 IOPS |        563 IOPS |  13442 IOPS |
>>> |      1024 KB |      5050 IOPS |        465 IOPS |  13887 IOPS |
>>> |      2048 KB |      2465 IOPS |        271 IOPS |  13885 IOPS |
>>> |--------------+----------------+-----------------+-------------|
>>>
>>> There's obviously no backing image, and only the last column uses
>>> handle_alloc_space() / fallocate().
>>
>> Thanks for providing some numbers!
>>
>> It was my impression, too, that subclusters wouldn’t solve it.  But it
>> didn’t seem like that big of a difference to me.  Did you run this
>> with aio=native?  (Because that’s where we have the XFS problem)
> 
> Here's with aio=native
> 
> |--------------+----------------+-----------------+-------------|
> | Cluster size | subclusters=on | subclusters=off | fallocate() |
> |--------------+----------------+-----------------+-------------|
> |       256 KB |     19897 IOPS |        891 IOPS |  32194 IOPS |
> |       512 KB |     17881 IOPS |        436 IOPS |  33092 IOPS |
> |      1024 KB |     17050 IOPS |        341 IOPS |  32768 IOPS |
> |      2048 KB |      7854 IOPS |        207 IOPS |  30944 IOPS |
> |--------------+----------------+-----------------+-------------|

OK, thanks again. :-)

So it seems right not to revert the commit and just work around the XFS
bug in file-posix.

Max

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