Re: squashfs performance regression and readahea

[Phillip Lougher]

On 10/05/2022 03:35, Matthew Wilcox wrote:
> On Tue, May 10, 2022 at 02:11:41AM +0100, Phillip Lougher wrote:
> > On 09/05/2022 14:21, Matthew Wilcox wrote:
> > > On Mon, May 09, 2022 at 08:43:45PM +0800, Xiongwei Song wrote:
> > > > Hi Hsin-Yi and Matthew,
> > > >
> > > > With the patch from the attachment on linux 5.10, ran the command as I
> > > > mentioned earlier,
> > > > got the results below:
> > > > 1:40.65 (1m + 40.65s)
> > > > 1:10.12
> > > > 1:11.10
> > > > 1:11.47
> > > > 1:11.59
> > > > 1:11.94
> > > > 1:11.86
> > > > 1:12.04
> > > > 1:12.21
> > > > 1:12.06
> > > >
> > > > The performance has improved obviously, but compared to linux 4.18, the
> > > > performance is not so good.
> > > >
> > > > Moreover, I wanted to test on linux 5.18. But I think I should revert
> > > > 9eec1d897139 ("squashfs: provide backing_dev_info in order to disable
> > > > read-ahead"),
> > > > right?  Otherwise, the patch doesn't work?
> > >
> > > I've never seen patch 9eec1d897139 before.  If you're going to point
> > > out bugs in my code, at least have the decency to cc me on it.  It
> > > should never have gone in, and should be reverted so the problem can
> > > be fixed properly.
> >
> > You are not in charge of what patches goes into Squashfs, that is my
> > perogative as maintainer of Squashfs.
>
> I think you mean 'prerogative'.  And, no, your filesystem is not your
> little fiefdom, it's part of a collaborative effort.

This isn't a spelling contest, and if that's the best you can do you
have already failed.

Be carefull here also, I have been maintainer of Squashfs for 20 years,
and was kernel maintainer for both Ubuntu and Redhat for 10 years, and
so I am experienced member of the community.

You reply is bordering on offensive and arrogant, especially considering
it is unwarranted.  I did not set out to offend you, and I don't
appreciate it.

About 8 years ago I decided to refrain from active involvement in the
kernel community, because I decided the level of discourse was
disgusting, and I had enough of it.

I poped up now to defend my approval of the Huawei patch.  I am *quite*
happy not to have any more involvement until necessary.

So having said what I want to say, I will leave it at that. You have
just proved why I have minimised my involvement.

No doubt you'll throw your toys out the pram, but, I'm no
longer listening so don't bother.


> > That patch (by Huawei) fixes the performance regression in Squashfs
> > by disabling readahead, and it is good workaround until something
> > better.
>
> You *didn't even report the problem to me*.  How can it be fixed if I'm
> not aware of it?

There was a email discussion last year, which I responded to, and got
ignored.  I will find it out tomorrow, perhaps.  But I will probably
not bother, because life is too short.

Cheers

Phillip