Re: Raid6 check performance regression 5.15 -> 5.16

Re: Raid6 check performance regression 5.15 -> 5.16

[Thorsten Leemhuis]

[TLDR: I'm adding the regression report below to regzbot, the Linux
kernel regression tracking bot; all text you find below is compiled from
a few templates paragraphs you might have encountered already already
from similar mails.]

On 07.03.22 19:15, Larkin Lowrey wrote:
> I am seeing a 'check' speed regression between kernels 5.15 and 5.16.
> One host with a 20 drive array went from 170MB/s to 11MB/s. Another host
> with a 15 drive array went from 180MB/s to 43MB/s. In both cases the
> arrays are almost completely idle. I can flip between the two kernels
> with no other changes and observe the performance changes.
> 
> Is this a known issue?

Hi, this is your Linux kernel regression tracker.

Thanks for the report.

CCing the regression mailing list, as it should be in the loop for all
regressions, as explained here:
https://www.kernel.org/doc/html/latest/admin-guide/reporting-issues.html

To be sure below issue doesn't fall through the cracks unnoticed, I'm
adding it to regzbot, my Linux kernel regression tracking bot:

#regzbot ^introduced v5.15..v5.16
#regzbot title md: Raid6 check performance regression
#regzbot ignore-activity

If it turns out this isn't a regression, free free to remove it from the
tracking by sending a reply to this thread containing a paragraph like
"#regzbot invalid: reason why this is invalid" (without the quotes).

Reminder for developers: when fixing the issue, please add a 'Link:'
tags pointing to the report (the mail quoted above) using
lore.kernel.org/r/, as explained in
'Documentation/process/submitting-patches.rst' and
'Documentation/process/5.Posting.rst'. Regzbot needs them to
automatically connect reports with fixes, but they are useful in
general, too.

I'm sending this to everyone that got the initial report, to make
everyone aware of the tracking. I also hope that messages like this
motivate people to directly get at least the regression mailing list and
ideally even regzbot involved when dealing with regressions, as messages
like this wouldn't be needed then. And don't worry, if I need to send
other mails regarding this regression only relevant for regzbot I'll
send them to the regressions lists only (with a tag in the subject so
people can filter them away). With a bit of luck no such messages will
be needed anyway.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

P.S.: As the Linux kernel's regression tracker I'm getting a lot of
reports on my table. I can only look briefly into most of them and lack
knowledge about most of the areas they concern. I thus unfortunately
will sometimes get things wrong or miss something important. I hope
that's not the case here; if you think it is, don't hesitate to tell me
in a public reply, it's in everyone's interest to set the public record
straight.

-- 
Additional information about regzbot:

If you want to know more about regzbot, check out its web-interface, the
getting start guide, and the references documentation:

https://linux-regtracking.leemhuis.info/regzbot/
https://gitlab.com/knurd42/regzbot/-/blob/main/docs/getting_started.md
https://gitlab.com/knurd42/regzbot/-/blob/main/docs/reference.md

The last two documents will explain how you can interact with regzbot
yourself if your want to.

Hint for reporters: when reporting a regression it's in your interest to
CC the regression list and tell regzbot about the issue, as that ensures
the regression makes it onto the radar of the Linux kernel's regression
tracker -- that's in your interest, as it ensures your report won't fall
through the cracks unnoticed.

Hint for developers: you normally don't need to care about regzbot once
it's involved. Fix the issue as you normally would, just remember to
include 'Link:' tag in the patch descriptions pointing to all reports
about the issue. This has been expected from developers even before
regzbot showed up for reasons explained in
'Documentation/process/submitting-patches.rst' and
'Documentation/process/5.Posting.rst'.

Re: Raid6 check performance regression 5.15 -> 5.16 #forregzbot

[Thorsten Leemhuis]

TWIMC: this mail is primarily send for documentation purposes and for
regzbot, my Linux kernel regression tracking bot. These mails usually
contain '#forregzbot' in the subject, to make them easy to spot and filter.

#regzbot fixed-by: 26fed4ac4eab09c27

On 08.03.22 06:44, Thorsten Leemhuis wrote:
> [TLDR: I'm adding the regression report below to regzbot, the Linux
> kernel regression tracking bot; all text you find below is compiled from
> a few templates paragraphs you might have encountered already already
> from similar mails.]
> 
> On 07.03.22 19:15, Larkin Lowrey wrote:
>> I am seeing a 'check' speed regression between kernels 5.15 and 5.16.
>> One host with a 20 drive array went from 170MB/s to 11MB/s. Another host
>> with a 15 drive array went from 180MB/s to 43MB/s. In both cases the
>> arrays are almost completely idle. I can flip between the two kernels
>> with no other changes and observe the performance changes.
>>
>> Is this a known issue?
> 
> Hi, this is your Linux kernel regression tracker.
> 
> Thanks for the report.
> 
> CCing the regression mailing list, as it should be in the loop for all
> regressions, as explained here:
> https://www.kernel.org/doc/html/latest/admin-guide/reporting-issues.html
> 
> To be sure below issue doesn't fall through the cracks unnoticed, I'm
> adding it to regzbot, my Linux kernel regression tracking bot:
> 
> #regzbot ^introduced v5.15..v5.16
> #regzbot title md: Raid6 check performance regression
> #regzbot ignore-activity
> 
> If it turns out this isn't a regression, free free to remove it from the
> tracking by sending a reply to this thread containing a paragraph like
> "#regzbot invalid: reason why this is invalid" (without the quotes).
> 
> Reminder for developers: when fixing the issue, please add a 'Link:'
> tags pointing to the report (the mail quoted above) using
> lore.kernel.org/r/, as explained in
> 'Documentation/process/submitting-patches.rst' and
> 'Documentation/process/5.Posting.rst'. Regzbot needs them to
> automatically connect reports with fixes, but they are useful in
> general, too.
> 
> I'm sending this to everyone that got the initial report, to make
> everyone aware of the tracking. I also hope that messages like this
> motivate people to directly get at least the regression mailing list and
> ideally even regzbot involved when dealing with regressions, as messages
> like this wouldn't be needed then. And don't worry, if I need to send
> other mails regarding this regression only relevant for regzbot I'll
> send them to the regressions lists only (with a tag in the subject so
> people can filter them away). With a bit of luck no such messages will
> be needed anyway.
> 
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> 
> P.S.: As the Linux kernel's regression tracker I'm getting a lot of
> reports on my table. I can only look briefly into most of them and lack
> knowledge about most of the areas they concern. I thus unfortunately
> will sometimes get things wrong or miss something important. I hope
> that's not the case here; if you think it is, don't hesitate to tell me
> in a public reply, it's in everyone's interest to set the public record
> straight.
>