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Message-ID: <1dff431e-f51d-edb0-5abc-353ceeef50ed@squashfs.org.uk>
Date:   Tue, 10 May 2022 04:20:18 +0100
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Subject: Re: squashfs performance regression and readahea
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Xiongwei Song <sxwjean@gmail.com>,
        Zheng Liang <zhengliang6@huawei.com>,
        Zhang Yi <yi.zhang@huawei.com>, Hou Tao <houtao1@huawei.com>,
        Miao Xie <miaoxie@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        "Song, Xiongwei" <Xiongwei.Song@windriver.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "squashfs-devel@lists.sourceforge.net" 
        <squashfs-devel@lists.sourceforge.net>,
        open list <linux-kernel@vger.kernel.org>
References: <PH0PR11MB519282C2834C7BB7B5431F34ECC79@PH0PR11MB5192.namprd11.prod.outlook.com>
 <Ynfzh2ifG85MZEoN@casper.infradead.org>
 <CAJMQK-jNYoJVqsri4REV=E3bG8AS7T82HrVSAUPzbUiWask01A@mail.gmail.com>
 <CAJMQK-i3OQxcG7=LzTG4k70BP0j6PstWw0C45xcEi6iVLn_2ag@mail.gmail.com>
 <CAEVVKH-m+3+xJMbM1vRM3d=AaPSv2xg4Qx8_WPw_29JByONS8A@mail.gmail.com>
 <YnkVaGB74xqWJqdG@casper.infradead.org>
 <13af40a9-6b60-6875-8326-0827e34182d5@squashfs.org.uk>
 <YnnPYD+VtQB6hlnL@casper.infradead.org>
From:   Phillip Lougher <phillip@squashfs.org.uk>
In-Reply-To: <YnnPYD+VtQB6hlnL@casper.infradead.org>
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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