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From Ben Slater <ben.sla...@instaclustr.com>
Subject Re: Meltdown/Spectre Linux patch - Performance impact on Cassandra?
Date Fri, 12 Jan 2018 22:36:32 GMT
We’re seeing evidence across our fleet that AWS has rolled something out in
the last 24 hours that has significantly reduce the performance impacts -
back pretty close to pre-patch levels. Yet to see if the impacts come back
with o/s patching on top of the improved hypervisor.

Cheers
Ben



On Thu, 11 Jan 2018 at 05:32 Jon Haddad <jon@jonhaddad.com> wrote:

> For what it’s worth, we (TLP) just posted some results comparing pre and
> post meltdown statistics:
> http://thelastpickle.com/blog/2018/01/10/meltdown-impact-on-latency.html
>
>
> On Jan 10, 2018, at 1:57 AM, Steinmaurer, Thomas <
> thomas.steinmaurer@dynatrace.com> wrote:
>
> m4.xlarge do have PCID to my knowledge, but possibly we need a rather new
> kernel 4.14. But I fail to see how this could help anyway, cause this looks
> highly Amazon Hypervisor patch related and we do not have the production
> instances patched at OS/VM level (yet).
>
> Thomas
>
> *From:* Dor Laor [mailto:dor@scylladb.com <dor@scylladb.com>]
> *Sent:* Dienstag, 09. Jänner 2018 19:30
> *To:* user@cassandra.apache.org
> *Subject:* Re: Meltdown/Spectre Linux patch - Performance impact on
> Cassandra?
>
> Make sure you pick instances with PCID cpu capability, their TLB overhead
> flush
> overhead is much smaller
>
> On Tue, Jan 9, 2018 at 2:04 AM, Steinmaurer, Thomas <
> thomas.steinmaurer@dynatrace.com> wrote:
>
> Quick follow up.
>
> Others in AWS reporting/seeing something similar, e.g.:
> https://twitter.com/BenBromhead/status/950245250504601600
>
> So, while we have seen an relative CPU increase of ~ 50% since Jan 4,
> 2018, we now also have applied a kernel update at OS/VM level on a single
> node (loadtest and not production though), thus more or less double patched
> now. Additional CPU impact by OS/VM level kernel patching is more or less
> negligible, so looks highly Hypervisor related.
>
> Regards,
> Thomas
>
> *From:* Steinmaurer, Thomas [mailto:thomas.steinmaurer@dynatrace.com]
> *Sent:* Freitag, 05. Jänner 2018 12:09
> *To:* user@cassandra.apache.org
> *Subject:* Meltdown/Spectre Linux patch - Performance impact on Cassandra?
>
> 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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-- 


*Ben Slater*

*Chief Product Officer <https://www.instaclustr.com/>*

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