Re: [PATCH 39/43] xfs: support write life time based data placement

Hans Holmberg
2025-02-13T13:03:35Z

On 13/02/2025 05:42, Darrick J. Wong wrote:
> On Wed, Feb 12, 2025 at 01:29:21PM +0000, Hans Holmberg wrote:
>> On 12/02/2025 01:27, Darrick J. Wong wrote:
>>> On Thu, Feb 06, 2025 at 07:44:55AM +0100, Christoph Hellwig wrote:
>>>> From: Hans Holmberg <hans.holmberg@wdc.com>
>>>>
>>>> Add a file write life time data placement allocation scheme that aims to
>>>> minimize fragmentation and thereby to do two things:
>>>>
>>>> a) separate file data to different zones when possible.
>>>> b) colocate file data of similar life times when feasible.
>>>>
>>>> To get best results, average file sizes should align with the zone
>>>> capacity that is reported through the XFS_IOC_FSGEOMETRY ioctl.
>>>>
>>>> For RocksDB using leveled compaction, the lifetime hints can improve
>>>> throughput for overwrite workloads at 80% file system utilization by
>>>> ~10%.
>>>
>>> The code changes look mostly ok, but how does it do at 40% utilization?
>>> 99%? Does it reduce the amount of relocation work that the gc must do?
>>
>> The improvement in data placement efficiency will always be there,
>> reducing the number of blocks requiring relocation by GC, but the impact
>> on performance varies depending on how full the file system is.
>>
>> At 40% utilization there is almost no garbage collection going on, so the
>> impact on throughput is not significant. At 99% the effects of better
>> data placement should be higher.
>
> <nod> Would you mind pasting that into the commit message?
>

That sounds like good idea. Christoph: could you fold in the above lines
into the commit message for the next iteration of the series?
(Or do you want an updated patch?)