Re: LIO/sec per CPU limit? Is it Hardware or Oracle code?

Hello Henry,

> 1. Our sysadm said that there are kernel issues and "perf stat" cannot run on these systems

I really would like to hear about these kernel issues and his concerns - never seen an issue with these.

> Also RAPL throttling is on in the slow server. I am guessing this could account for the throttled cpu speed. I am starting to google search to see where this can be set from. Anyone out there know any  good resources on RAPL throttling or how to disable it?

Unfortunately you have not mentioned your linux kernel version yet (or i just missed it) but there are several ways to drill down into RAPL.

1. PowerCap interface: https://www.kernel.org/doc/Documentation/power/powercap/powercap.txt
2. Perf
3. MSR registers (/dev/msr)

However if you can do the fancy stuff at all depends on BIOS (and vendor). If you run dmesg you may see some messages about "intel_rapl" to get an idea if it works anyway with your hardware.

Best Regards
Stefan Koehler

Independent Oracle performance consultant and researcher Website: http://www.soocs.de
Twitter: _at_OracleSK

> Henry Poras <henry.poras_at_gmail.com> hat am 5. September 2017 um 06:39 geschrieben:
>
> Figured it was time to send the list an update.
> 1. Our sysadm said that there are kernel issues and "perf stat" cannot run on these systems
> 2. I installed a slob instance on both a fast and slow server. There was no way to stop our workload from running, but I ran slob multiple times, trying to keep each run short (~3 minutes) so the underlying workload would not vary much. Also tried running when the load was relatively low. All of the run results were pretty consistent with one another. Configuring SLOB to run strictly LIO, I saw ~4M lio/sec vs. 1.5M lio/sec
> 3. Our sysadm did get turbostat installed. What I take as the most important output from that was:
> slow: TSC_MHz - 2600     Bzy_MHz - 1200   PKG_% - 100%
> fast:  TSC_MHz - 2606     Bzy_MHz - 3110    PKG_% - 0%
>
> So the clock speeds are nearly identical, ,but the running speeds when busy are very different. Also RAPL throttling is on in the slow server. I am guessing this could account for the throttled cpu speed. I am starting to google search to see where this can be set from. Anyone out there know any  good resources on RAPL throttling or how to disable it?
>
> Thanks.
>
> Henry

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