Friday May 08, 2009

Observing Intel's "Turbo Boost" feature with PowerTOP

One of the most interesting features of Intel's Core i7 and the Xeon 5500 processors (Nehalem) is the ability of the processor to go into a mode called "Turbo Boost". While most modern processors are capable of being power managed to run at various clock frequencies, "Turbo Boost" is different, as it allows the processor to autonomously run at a higher clock speed than would otherwise be available in the processor's maximum performance power management state (P0).

Here's how it works. When one or more of the cores on the processor is in the P0 (max perf) state, those cores may enter Turbo Boost mode, allowing them to run at the faster clock frequency. "How much faster" depends on how much power and thermal headroom is available, but in general, the more cores there are on the socket that are idle and power managed (via. C-states), the faster the remaining running core(s) will go. With the introduction of OpenSolaris support for Deep C-states which integrated in build 110, we're certainly seeing the effects...since the system is now readily taking advantage of the deeper C-states, turbo boost happens all the time. :)

But how does one observe this? It's certainly useful to know when Turbo Boost is happening, and how much of an "overclock" the processor is achieving. Fortunately, in build 110 Rafael Vanoni pushed some changes to PowerTOP that provides this observability:

This is a screenshot of PowerTOP running on a Xeon 5500 (Nehalem) based system. Notice in the P-states (Frequencies) column that the highest clock speed has (turbo) next to it. As turbo mode is entered, PowerTOP will track the average frequency of the system's processors over the sampling interval. You can actually watch that top end frequency fluctuate as utilization across the system changes.

Clearly, this observability is important for understanding system performance (but more importantly, for performance determinism). Very cool stuff...and yes, this will be present in the upcoming OpenSolaris release. Here's a video we did in which Rafael talks more about this...


Technorati Tags: OpenSolaris

Tuesday May 29, 2007

Simon Phipps featured in Linux Journal, and other delights

Over the weekend my wife and were kicking around at the Mercado shopping center in Santa Clara. It's one of those shopping centers that has appeal for both of us...Micro Center for me, and TJ Maxx for her. :) After delighting in finding of a 2GB USB flash drive for $16, I was further delighted to see this month's Linux Journal in which an interview with Simon Phipps is featured. Fostering OpenSolaris awareness in the Linux community is a good thing, so it was nice to see a good amount of discussion there. I look forward to the day where critical mass is such that more OpenSolaris magazine articles (and perhaps dedicated magazines) begin to surface. It really was nice to see.
Technorati Tags: OpenSolaris

Sunday May 06, 2007

Inspiration strikes (but caffeine helps)

Argh, my poor neglected blog. Pulling it up after all this time, I didn't even look at the date of the last entry, and I think i'll keep it that way. With any luck, i'll post enough entries soon enough that by the time I look, I won't feel like more of a slacker than I already do. But at least i'm here now (thanks partially goes to the chocolate covered espresso beans I happened acress a few hours ago). It's past midnight and i'm fairly wired...so it's a perfect time to bring things up to date.

"Eric Saxe's Blog" doesn't cut it. We need a proper title. Hmm...:

YOUR ACCESS SUSPENDED
PLEASE REPORT TO DILLINGER IMMEDIATELY
AUTHORIZATION: MASTER CONTROL PROGRAM

END OF LINE

What better way to engross an impressionable, video game loving 7 year boy with computers than to tell him that inside that unassuming white box programs in glowing red and blue suits were battling it out in a video game arena? For better or worse, the nostalgia of the time is still with me 26 years later. :) Campy? Perhaps, but who's to say that without such inspiration i'd be doing what I love today?

Thursday Jun 16, 2005

And now for these messages...

I'd like to encourage anyone with an interest in [Open]Solaris performance to participate in the performance community at opensolaris.org. From there you can join the discussion list, raise issues, ask questions, and exchange ideas.

Much of the Kernel Performance Group (my group) is already heavily involved with the community and OpenSolaris in general. We're very interested in externalizing much of what has (before OpenSolaris) been quite internal. At our project team meeting yesterday we tossed around some ideas for how we could open up some of our meetings to the community. Very exciting indeed!!

Wednesday Jan 26, 2005

Welcome!

My name is Eric Saxe.

I've been with Sun for 5 years, the last 3.5 of which i've been doing development on the Solaris Kernel. Most of my development efforts are dedicated towards streamlining the kernel's scheduling and dispatching policies. Scheduling policy dictates when threads run (priorities), and dispatching deals with the "where" (on which CPUs) part.

This has become especially interesting work over the last few years as various non-uniformities have crept their way into the system's memory and processor architectures. Non-uniformity in the memory side of things has blessed us with NUMA, and has more recently emerged on the processor side though Simultaneous Multi-Threading (SMT), Chip Multi-Processor (CMP), and threaded multi-core processor architectures.

I'm looking forward to talking more about how these non-uniformites can impact application and system performance, as well as how the Solaris kernel adapts in a future post.

But for now, welcome!
About

esaxe

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