Re: [LKP] Re: [xfs] bad77c375e: stress-ng.fallocate.ops_per_sec -10.0% regression

[Dave Chinner]

On Tue, Nov 30, 2021 at 02:46:06PM +0800, Xing Zhengjun wrote:
> Hi Dave,
> 
>    Do you have time to look at this? It still existed in v5.16-rc3. Thanks

AFAIC, it's a "don't care" issue.

The series of commits around this one:

> > > FYI, we noticed a -10.0% regression of
> > > stress-ng.fallocate.ops_per_sec due to commit:
> > > 
> > > 
> > > commit: bad77c375e8de6c776c848e443f7dc2d0d909be5 ("xfs: CIL
> > > checkpoint flushes caches unconditionally")
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

changed how we manage FUA/cache flushes for the journal changed
performance across a wide range of workloads. Many went a lot
faster, some (like this one) went slightly slower. Overall it was a
net win, especially on storage stacks with really slow cache flushes
(e.g. dm-thinp) and workloads that do a lot of concurrent metadata
modification.

Overall, fallocate is not a performance critical path - it's a
slowpath because it serialises all IO to that file while the
fallocate call runs. Hence performance characteristics for fallocate
aren't really a major concern to begin with...

-Dave.
-- 
Dave Chinner
dchinner@xxxxxxxxxx