williamhathaway.com

I attended a Sun presentation on DTrace today. Here are links to some good resources:

• OpenSolaris DTrace Community
• Solaris Internals DTrace Topics
• DTrace Toolkit
• Solaris Internals DTrace with Java
• OpenSolaris DTrace Discussion Forum

Some anecdotes that were mentioned:

Buffer sizes

When DTrace was fired up on some monster sized boxes (like a 144 core E25k), it took a while for DTrace to kick in. The issue turned out to be that, by default, DTrace allocates 4MB of memory for each core. On a 144 core machine, this means you need to get ~ 600MB allocated The presenter said he decided to lower the buffer size to 256k or so per CPU and that made DTrace start up much faster.

DTrace aborts on Opteron machines

If you are using dual-core Sun x4100 M2 or X4200 M2 servers and Solaris 10u3 or earlier, you will almost definitely get errors when trying to run DTrace where it aborts almost instantly. You are hitting:

bug id 6507659 tsc differences between CPU’s give dtrace_gethrtime() serious problems

The workaround (-w option) is mentioned in the ticket, but that also disables DTrace safety features, so use caution. If you are on Solaris 10u4 (aka 2008/07) or patched to 120012-14, you should be fine and won’t need the workaround.

Which probes are safe for production?

Probe effect is almost entirely a function of how often they get called. The presenter mentioned that using the syscall, io, and profile providers are almost always fine in production. He did mention that he would not recommend using the pid provider in most cases on a busy process in production, although the the only affect will be slowing the specific traced process down.

DTrace Toolkit

I really wanted to emphasize how good I think this collection of scripts/examples are. I consider it to be almost like the SE Toolkit of the DTrace world. Even if you have no desire to wade through the DTrace docs, or don’t consider yourself much of a scripter, take a look at the DTrace Toolkit and try running some of the examples.

Had a really good tempo workout today on the treadmill at the Philadelphia Courtyard Marriott.

Warm-up: 1/4 mile walking + 1 mile jog/run (pace between 12:00 and 8:00)

Tempo: 5 miles @ ~ 7:00/pace (heart rate averaged 159)

Cool-down: 2 miles (pace between 12:00 and 10:00)

I felt really strong during the tempo portion and was tempted to increase the distance, but given the string of minor injuries I’ve had lately, I decided to end it right at 5 miles. There was a decent difference between what the treadmill was measuring for speed and what my footpod measured (treadmill had mile 5 @ ~ 6:36 and footpod recorded 6:56). I took the more conservative footpod pace, which I’m hoping is accurate to within a percent or two, since I calibrated it outside at the same pace two weeks ago.

Plan for tomorrow: 3-5 miles @ recovery pace (heart rate staying below 140).

I’ve been blog negligent for a little while, here is a recap of my last two weeks:

My left quad has been hurting a bit during some of the harder workouts. I took 2 days off, then did two easy days.

On 1/31- LA Fitness – 7.5 miles including 5 tempo miles @ 7:00/pace and felt good (no quad pain)

2/01 – LA Fitness – 1/2 mile warmup, 2.5 miles @ 8:34/pace, 1 hour 3 person racquetball (no quad pain)

2/02 – Ran with Jon L in Harrisburg – 8.5 miles averaging 8:30, last two miles were around 8:00.

2/03 – Plan was for 10 miles @ 7:25/pace. Headed out to Conewago, but was on a tight schedule to go with my wife to ChocolateFest in Hershey. I was on track and feeling comfortable for first 6 miles. A bit after the 7th mile started, I could feel a twinge in my left quad. I felt the pain staying, and stopped at around 7.5 miles (2.5 from my car). I started walking back toward the car so as not to aggravate the muscle, but I realized if I walked back, it would take too long and we would be really late to our time-limited ChocolateFest session. I ended up jogging back about 2.4 miles. In retrospect, I really wish I had taken 02/02 off, but I thought before hand that our pace would have been slower (we were averaging about 30-40 seconds a mile slower the previous weeks, Jon’s conditioning is coming back).

02/04 – Off

02/05 – Off

02/06 – AM – 3 miles @ 8:30 pace on treadmill in Philadelphia. Felt fine, cut it short to head to work.

02/06 – PM – 5.35 miles @ 8:30 pace on treadmill in Philadelphia. Felt fine.

02/07 – PM – 6 miles @ 8:30 pace on treadmill in Philadelphia. Felt fine.

02/08 – Off

02/09 – Appalachian Trail run near rt 850 with Jon L and James L. It had snowed in the morning and the trail was nice and runnable for the first 1.5 miles. It then had a lot of sections that were really rocky and some crazy steep parts too. We ran 8.3 miles in 1:44 (about 12:30 miles). The snow made the trail extremely slippery, and my ankles were getting badly beaten up (James was running behind me for a bit and said he kept expecting me to blow out an ankle). I definitely need to pick up some trail shoes this week (which will be easy, since I will be working less than two minutes from the Philadelphia Runner store). My ankles felt better later in the day, no quad pain.

02/10 – Ran 5 miles at the Carlisle Barracks with Nate and Eric at 8AM. Pretty enjoyable time, averaged just under 9:00/pace. Played racquetball with Mark for an hour in the afternoon (112 BPM). We were tied 2 games each, but had to stop because our time was up and other people had the court. No quad pain.