Re: [PATCH 4/4] sched/fair: Proportional newidle balance

Mohamed Abuelfotoh, Hazem
2026-02-04T13:59:45Z

On 04/02/2026 13:27, Peter Zijlstra wrote:
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> On Wed, Feb 04, 2026 at 12:45:41PM +0000, Mohamed Abuelfotoh, Hazem wrote:
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>> Version | Benchmark name | SUT EC2 Instance| diff %
>> v6.12.66 | postgresql | c7a.4xlarge | -4.0%
>> v6.12.66 | nginx_lb | c7a.4xlarge | -5.0%
>> v6.12.66 | memcached | c7a.4xlarge | -11.0%
>> v6.12.66_proposed | postgresql | c7a.4xlarge | -4.0%
>> v6.12.66_proposed | nginx_lb | c7a.4xlarge | -5.0%
>> v6.12.66_proposed | memcached | c7a.4xlarge | -13.0%
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> *sigh*, that actually made it worse for memcached :/ I'm not familiar
> with the memcached benchmark, is this something I can run on a single
> machine, or does it require high speed networking and 2 machines?

Yup that's true it's slightly worse on memcached with the proposed fix:(
The memcached benchmark is kind of multi-layer test where you need at at
least 2 client machines and 1 server machine and 1 machine as a test
coordinator. The server VM is able to achieve 12.5 Gbps of network
bandwidth and the client each one is able to achieve 30 Gbps so I think
it will be tricky and likely impossible to reproduce this on a single
machine. I will try to come-up with standalone reproduction steps that
can be used to investigate this memcached regression. Meanwhile we will
share the fio regression reproduction steps that I mentioned in my
previous update. This should be much simpler in steps and can be done on
a single machine.