Memory coherency issue with IO thread offloading?

[Jens Axboe]

On 3/24/23 6:15 PM, Michael Ellerman wrote:
> Jens Axboe <axboe at kernel.dk> writes:
>> On 3/24/23 1:27?AM, Christophe Leroy wrote:
>>> Le 23/03/2023 ? 19:54, Jens Axboe a ?crit :
>>>> I got a report sent to me from mariadb, in where 5.10.158 works fine and
>>>> 5.10.162 is broken. And in fact, current 6.3-rc also fails the test
>>>> case. Beware that this email is long, as I'm trying to include
>>>> everything that may be relevant...
>>>
>>> Which variant of powerpc ? 32 or 64 bits ? Book3S or BookE ?
>>
>> I knew I'd forget something important... It's power9:
>>
>> processor	: 0
>> cpu		: POWER9 (architected), altivec supported
>> clock		: 2200.000000MHz
>> revision	: 2.2 (pvr 004e 1202)
> 
> Believe it or not there's still more variables in play, Power9 has two
> different MMUs, and Linux can run on two different hypervisors as well
> as on bare metal P9 :)

Just my luck :-)

> 
> Can you paste the last ~10 lines of /proc/cpuinfo, with the "machine",
> "firmware" and "MMU" lines, that should tell us everything we need to
> know.

timebase	: 512000000
platform	: pSeries
model		: IBM pSeries (emulated by qemu)
machine		: CHRP IBM pSeries (emulated by qemu)
MMU		: Radix

I know it reproduces bare metal as well, but no details on what
that box is. I just know I was able to reproduce it in this vm that
I was able to get my hands on.

-- 
Jens Axboe