Re: AMD Shanghai versus Intel Nehalem

On 13-5-2009 20:39 Scott Carey wrote:
> 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).

Apart from that, it has a newer debian (and thus kernel/glibc) and a
slightly less constraining IO which may help as well.

> 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>

It is in use, so the results may not be so good, this is the best I got
on our dual X5355:
  Timing cached reads:   6314 MB in  2.00 seconds = 3159.08 MB/sec

But this is the best I got for a (also in use) Dual E5450 we have:
  Timing cached reads:   13158 MB in  2.00 seconds = 6587.11 MB/sec

And here the best for the (idle) E5540:
  Timing cached reads:   16494 MB in  2.00 seconds = 8256.27 MB/sec

These numbers are with hdparm v8.9

Best regards,

Arjen