Hi Thomas,

No clue about AWS, and it is of course highly dependent on hardware, but on
CentOS 7 on bare metal, the patched kernel
(kernel-3.10.0-693.11.6.el7.x86_64) seems to have a roughly 50% CPU
increase compared to an unpatched kernel
(kernel-3.10.0-693.11.1.el7.x86_64). On a happier note, the latest mainline
kernel from elrepo (kernel-ml-4.14.11-1.el7.elrepo.x86_64) seems to recover
the entire performance loss, likely due to recent PCID patches (or the
other 3+ years of kernel development).

That's on lab servers though, the numbers here will likely vary a lot based
on test setup, and may not be reproducible for production workloads.

If you have the infrastructure to test a variety of kernels, I'd be very
interested to see your numbers.


Tom van der Woerdt
Site Reliability Engineer

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On Fri, Jan 5, 2018 at 12:09 PM, Steinmaurer, Thomas <
thomas.steinmau...@dynatrace.com> wrote:

> Hello,
> has anybody already some experience/results if a patched Linux kernel
> regarding Meltdown/Spectre is affecting performance of Cassandra negatively?
> In production, all nodes running in AWS with m4.xlarge, we see up to a 50%
> relative (e.g. AVG CPU from 40% => 60%) CPU increase since Jan 4, 2018,
> most likely correlating with Amazon finished patching the underlying
> Hypervisor infrastructure …
> Anybody else seeing a similar CPU increase?
> Thanks,
> Thomas
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