Re: Also seeing 2 x quad-core system slower that 2 x dual core

Matt Reimer wrote:
On Nov 29, 2007 10:58 AM, Kris Kennaway <kris@xxxxxxxxxxx> wrote:
Pete French wrote:
On the dual core processors this takes about 20 seconds. On the quad
cores it takes about 3 minutes! This is true for both the 32 and 64 bit
versions of FreeBSD :-(
That almost certainly has nothing to do with how many CPUs your system
has, since rm -rf is a single process running on a single core.

I wonder if I'm seeing this too. Running super-smack on a 2 x quad
core 1.6GHz Dell 1950 I get about 40000 qps, whereas on a 2 x dual
core 3.0GHz box I've seen 80000 qps.

Please, let's try to stay focused :) rm -rf has nothing to do with super-smack and vice versa.

> Is this expected?

It is not very surprising. super-smack is not a good SMP benchmark, it does stupid things like 1-byte I/O, so it is not very scalable nor a good model of real-world database activity. Accounting for your CPUs being twice as fast on the dual core, it roughly says that the benchmark is not scaling beyond 4 CPUs, which is in line with my own observations.

Kris

_______________________________________________
freebsd-stable@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-stable
To unsubscribe, send any mail to "freebsd-stable-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • Re: Also seeing 2 x quad-core system slower that 2 x dual core
    ... since rm -rf is a single process running on a single core. ... Running super-smack on a 2 x quad ... Accounting for your CPUs ... being twice as fast on the dual core, it roughly says that the benchmark ...
    (freebsd-stable)
  • Re: Beyond multicore
    ... Using 200-odd pins to support a DDR-III ... device between this DRAM and the on-die Memory Controller. ... linear scaling) current 3 GHz CPUs need about 10 GBytes/sec of DRAM BW/ ... In order that each CPU core has about the same L-big ...
    (comp.arch)
  • Re: Beyond multicore
    ... Using 200-odd pins to support a DDR-III ... device between this DRAM and the on-die Memory Controller. ... linear scaling) current 3 GHz CPUs need about 10 GBytes/sec of DRAM BW/ ... In order that each CPU core has about the same L-big ...
    (comp.arch)
  • Re: Stupidest game of the month. 11 move Mate.
    ... Just to make it tougher for Sanny's 3000 rated chess program... ... Core 2 Duo, the java applet is using both CPUs. ...
    (rec.games.chess.computer)
  • Re: OO and IBM z series COBOL was Re: Discussions of COBOLphilospphy
    ... A COBOL program I run regularly seemed to be much ... each core seems to run at about half the single ... CPUs don't run at a constant clock speed. ... If someone misconfigured your motherboard, ...
    (comp.lang.cobol)