Re: Highly reflinked and fragmented considered harmful?

Chris Dunlop
2022-05-10T06:31:00Z

On Mon, May 09, 2022 at 10:10:57PM -0700, Darrick J. Wong wrote:
> On Tue, May 10, 2022 at 07:07:35AM +0300, Amir Goldstein wrote:
>> On Mon, May 09, 2022 at 12:46:59PM +1000, Chris Dunlop wrote:
>>> Is it to be expected that removing 29TB of highly reflinked and fragmented
>>> data could take days, the entire time blocking other tasks like "rm" and
>>> "df" on the same filesystem?
...
>> From a product POV, I think what should have happened here is that
>> freeing up the space would have taken 10 days in the background, but
>> otherwise, filesystem should not have been blocking other processes
>> for long periods of time.
>
> Indeed. Chris, do you happen to have the sysrq-w output handy? I'm
> curious if the stall warning backtraces all had xfs_inodegc_flush() in
> them, or were there other parts of the system stalling elsewhere too?
> 50 billion updates is a lot, but there shouldn't be stall warnings.

Sure: https://file.io/25za5BNBlnU8 (6.8M)

Of the 3677 tasks in there, only 38 do NOT show xfs_inodegc_flush().

> I bet, however, that you and everyone else would rather have somewhat
> inaccurate results than a load average of 4700 and a dead machine.

Yes, that would have been a nicer result.

Chris