Re: [linus:master] [vfs] 681ce86235: filebench.sum_operations/s -7.4% regression

[Yafang Shao]

On Thu, May 30, 2024 at 12:38 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Tue, 28 May 2024 at 22:52, kernel test robot <oliver.sang@xxxxxxxxx> wrote:
> >
> > kernel test robot noticed a -7.4% regression of filebench.sum_operations/s on:
> >
> > commit: 681ce8623567 ("vfs: Delete the associated dentry when deleting a file")
>
> Well, there we are. I guess I'm reverting this, and we're back to the
> drawing board for some of the other alternatives to fixing Yafang's
> issue.

Hi Linus,

I just checked the test case webproxy.f[0], which triggered the regression.

This test case follows a deletefile-createfile pattern, as shown below:

  - flowop deletefile name=deletefile1, filesetname=bigfileset
  - flowop createfile name=createfile1, filesetname=bigfileset, fd=1

It seems that this pattern is causing the regression. As we discussed
earlier, my patch might negatively impact this delete-create pattern.
The question is whether this scenario is something we need to address.
Perhaps it only occurs in this specific benchmark and doesn't
represent a real-world workload.

[0] https://github.com/filebench/filebench/blob/master/workloads/webproxy.f

>
> Al, did you decide on what approach you'd prefer?
>
>                      Linus



-- 
Regards
Yafang