On 7/24/23 9:48?AM, Greg KH wrote:
> On Mon, Jul 24, 2023 at 04:35:43PM +0100, Phil Elwell wrote:
>> Hi Andres,
>>
>> With this commit applied to the 6.1 and later kernels (others not
>> tested) the iowait time ("wa" field in top) in an ARM64 build running
>> on a 4 core CPU (a Raspberry Pi 4 B) increases to 25%, as if one core
>> is permanently blocked on I/O. The change can be observed after
>> installing mariadb-server (no configuration or use is required). After
>> reverting just this commit, "wa" drops to zero again.
>
> This has been discussed already:
> https://lore.kernel.org/r/12251678.O9o76ZdvQC@xxxxxxxxxxxxxx
>
> It's not a bug, mariadb does have pending I/O, so the report is correct,
> but the CPU isn't blocked at all.
Indeed - only thing I can think of is perhaps mariadb is having a
separate thread waiting on the ring in perpetuity, regardless of whether
or not it currently has IO.
But yes, this is very much ado about nothing...
--
Jens Axboe
