IT @ AnandTech: Sun’s T2000 “Coolthreads” Server: First Impressions and Experiences

The T2000 as a heavy SAMP web server: the results

To interpret the graphs below precisely, you must know that the x-axis gives you the number of demanded requests, and the y-axis gives you the actual reply rate of the server. So, the first points all show the same performance for each server, as each server is capable of responding fast enough.

We tested the Opteron machines with both Linux on Solaris to get an idea of the impact of the OS.

Click to enlarge.

The Sun T2000 isn't capable of beating our Quad core Opteron, but there are few remarks that I should make.

First of all, we tested the 1 GHz T1, which is, of course, about 20% slower than the best T1 at 1.2 GHz. The T2000 peaked at 950 req/s, the quad core Opteron at 1368 (Linux) and 1244 (Solaris) req/s. However, the T2000 was capable of delivering 935 req/s without any error (request timeout) while the Quad Opteron delivered 1100 (Solaris) and 1250 (linux) req/s without any errors. So, given the criteria that there cannot be any time-out, the difference gets a little bit smaller.

In defense of the Opteron and Xeon: the average response time for one particular request was (most of the time) between 5 and 15 ms. Once the server came close to its saturation point, we noted a maximum of 70 ms. With the T2000, the response time was at least 20 ms, typically 40 ms, with peaks of up to 220 ms when we came close to the peak throughput.

Of course, this is the disadvantage of the lower single-threaded performance of this server CPU: the individual response times are higher. In case of OLTP and web server, this is hardly a concern; in case of a decision support system, it might be one.

There is a better way to do this test, of course: enable the mod_deflate module and get some decent gzip compression. Once we enabled compression, our network I/O, which peaked at up to 12 MB/s, came down to a peak network I/O of 1.8 MB/s. Let us see the next benchmark, where we measured with gzip compression on.

Click to enlarge.

The Sun T1 starts to show what it can do: performance has hardly decreased. Gzip compression is almost free on the T1; compression lowers performance by only 2%. The Opteron sees its performance lowered by 21% (977 vs 1244), and the Xeon by 19% (730 vs 899).

On Solaris, the T1 performs like a quad Opteron. Linux, which has probably slightly better drivers for our Opteron server, gives the quad Opteron the edge.

Let analyse this a little further.

PHP/MySQL No Gzip
Single Opteron 275	665	4-core T1	535
Dual Opteron 275	1244	8-core T1	949
Scaling 2 Opteron cores to 4:	87%	Scaling 4 to 8 T1 cores:	77%

PHP/MySQL Gzip
Single Opteron 275	538	4-core T1	477
Dual Opteron 275	977	8-core T1	933
Scaling 2 Opteron cores to 4:	82%	Scaling 4 to 8 T1 cores:	96%

Gzip performance vs no Gzip
Opteron 275	79%	Sparc T1	98%

As you can see, our application should be a prime example of an application where multi-core server CPU feels at home. With Gzip compression enabled, performance is still almost perfect at 96% going from 4 to 8 T1 cores.

So, why aren't we seeing the performance that the Sun claims regarding, for example, Spec Web2005, where the T1 has no problem outperforming quad core x86 CPUs? We are not sure, as we measured that 97% of the processing was done in the OS code (97% "system") and only 2-3% of the CPU load was done in the actual application ("user"). We suspect that the relatively light load of FP operations might have lowered the T1's performance. Depending on the tool that we used, we saw 0.66 to 1% of FP operations in our instruction mix, with peaks to 2.4%. Those FP operations are a result of our script calculating averages most likely.