Re: AMD Shanghai versus Intel Nehalem

On 5/12/09 11:08 PM, "Arjen van der Meijden" <acmmailing(at)tweakers(dot)net>
wrote:

> We have a dual E5540 with 16GB (I think 1066Mhz) memory here, but no AMD
> Shanghai. We haven't done PostgreSQL benchmarks yet, but given the
> previous experiences, PostgreSQL should be equally faster compared to mysql.
>
> Our databasebenchmark is actually mostly a cpu/memory-benchmark.
> Comparing the results of the dual E5540 (2.53Ghz with HT enabled) to a
> dual Intel X5355 (2.6Ghz quad core two from 2007), the peek load has
> increased from somewhere between 7 and 10 concurrent clients to
> somewhere around 25, suggesting better scalable hardware. With the 25
> concurrent clients we handled 2.5 times the amount of queries/second
> compared to the 7 concurrent client-score for the X5355, both in MySQL
> 5.0.41. At 7 CC we still had 1.7 times the previous result.
>

Excellent! That is a pretty huge boost. I'm curious which aspects of this
new architecture helped the most. For Postgres, the following would seem
the most relevant:
1. Shared L3 cache per processors -- more efficient shared datastructure
access.
2. Faster atomic operations -- CompareAndSwap, etc are much faster.
3. Faster cache coherency.
4. Lower latency RAM with more overall bandwidth (Opteron style).

Can you do a quick and dirty memory bandwidth test? (assuming linux)
On the older X5355 machine and the newer E5540, try:
/sbin/hdparm -T /dev/sd<device>

Where <device> is a valid letter for a device on your system.

Here are the results for me on an older system with dual Intel E5335 (2Ghz,
4MB cache, family 6 model 15)
Best result out of 5 (its not all that consistent, + or minus 10%)
/dev/sda:
Timing cached reads: 10816 MB in 2.00 seconds = 5416.89 MB/sec

And a newer system with dual Xeon X5460 (3.16Ghz, 6MB cache, family 6 model
23)
Best of 7 results:
/dev/sdb:
Timing cached reads: 26252 MB in 1.99 seconds = 13174.42 MB/sec

Its not a very accurate measurement, but its quick and highlights relative
hardware differences very easily.

> I'm not really sure how the shanghai cpu's compare to those older
> X5355's, the AMD's should be faster, but how much?
>

I'm not sure either, and the Xeon platforms have evolved such that the
chipsets and RAM configurations matter as much as the processor does.

> I've no idea if we get a Shanghai to compare it with, but we will get a
> dual X5570 soon on which we'll repeat some of the tests, so that should
> at least help a bit with scaling the X5570-results around the world down.
>
> Best regards,
>
> Arjen
>