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Enthusiast

Monitoring CPU cache hits

Almost all servers have BIOS options to configure CPU cache and prefetching settings. IBM says these settings can affect performance as much as 20% and they should be configured according to your environment.

Is it possible for vCenter or ESX(i) to monitor the CPU cache hits? I'd like to test these settings but I need some way to monitor the results.

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J1mbo
Virtuoso
Virtuoso

Do you mean disk cache settings?

http://blog.peacon.co.uk

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Enthusiast
Enthusiast

CPU cache settings, not disk.

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J1mbo
Virtuoso
Virtuoso

What are your BIOS options?

http://blog.peacon.co.uk

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J1mbo
Virtuoso
Virtuoso

Also looks that this has come up before:

http://communities.vmware.com/message/832438

http://blog.peacon.co.uk

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Enthusiast
Enthusiast

On our newer servers we have the following options:

- Adjacent Cache Line Prefetch

- Hardware Prefetcher

- DCU Streamer Prefetcher

- Data Reuse

I know some of the older servers have different settings.

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Enthusiast
Enthusiast

Yea, I've seen that post before Smiley Wink

Actually, my post now is a bit different beccause now I want to validate the recommended settings.

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J1mbo
Virtuoso
Virtuoso

I'm not sure it would be possible to even gather the stats without additional hardware, since all this will be invisible to whatever is running. Also it strikes me that with a virtualisation layer coupled with hyperthreading, the cost of cache misses is potentially reduced (assuming there is something else queued with useful work).

I guess the only way to verify would be to create a repeatable workload and test overall utilisation rates and run times. You might be able to approximate that if you have prodiction workloads by just running them week-by-week with differing settings and comparing the weekly CPU stats perhaps.

http://blog.peacon.co.uk

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Enthusiast
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Correct, it must be ESX (or something at that level) that can monitor the CPU.

My plan is to setup multiple configurations, let them run, and capture the data. After a period of time, I'll review the data and see which configuration works best in our environment.

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