Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and SPECjvm2008 benchmarks against 4.6 kernel

[Branimir Maksimovic]

Could it be related to this:

https://www.phoronix.com/scan.php?page=news_item&px=P-State-Possible-4.6-Regression


On Thu, 16 Jun 2016 18:40:01 +0200
Jirka Hladky <jhladky@xxxxxxxxxx> wrote:

> Hello,
>
> we see performance drop 30-40% for SPECjbb2005 and SPECjvm2008
> benchmarks starting from 4.7.0-0.rc0 kernel compared to 4.6 kernel.
>
> We have tested kernels 4.7.0-0.rc1 and 4.7.0-0.rc3 and these are as
> well affected.
>
> We have observed the drop on variety of different x86_64 servers with
> different configuration (different CPU models, RAM sizes, both with
> Hyper Threading ON and OFF, different NUMA configurations (2 and 4
> NUMA nodes)
>
> Linpack and Stream benchmarks do not show any performance drop.
>
> The performance drop increases with higher number of threads. The
> maximum number of threads in each benchmark is the same as number of
> CPUs.
>
> We have opened a BZ to track the progress:
> https://bugzilla.kernel.org/show_bug.cgi?id=120481
>
> You can find more details along with graphs and tables there.
>
> Do you have any hints which commit should we try to reverse?
>
> Thanks a lot!
> Jirka