Messages in this thread |  | | Date | Sun, 4 Nov 2001 07:32:31 -0800 (PST) | From | John Alvord <> | Subject | Re: [khttpd-users] khttpd vs tux |
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On Sun, 4 Nov 2001, Erik Mouw wrote:
> On Sat, Nov 03, 2001 at 08:18:19PM +0100, Roy Sigurd Karlsbakk wrote: > > > Each GigE card will need its own 66MHz PCI bus. Each PCI bridge will need > > > to be coming off a memory bus that can sustain all of these and the CPU > > > at once. > > > > > > At that point it really doesnt look much like a PC. > > > > How much raw speed do you think I can manage to get out of a really cool > > n-way server from Compaq? I beleive we'll go for a Compaq server, as > > that's what's been decided some time ago. > > Not that much. Alan's point is that you're pushing the limit of the > memory bandwidth, not the number of CPUs. This is the single reason > that high traffic websites either use some serious non-PC hardware (IBM > Z-series, for example) or a large number of PCs in parallel to share > the load. > > > I read something by Linus about linux scalability, and I beleive he said > > that 'linux [2.4] scales good up to 4 cpus, but not that good futher on > > [to 8?]'. Can anyone fill in the holes here? > > The number of CPUs really doesn't matter in this case. With several > GigE cards memory bandwidth and latency is your main problem.
Interesting parallel...
In the last few years there have been multiple cases where people reported benchmarks where a dual processir gave less thruput then a single processor. In most cases, the single processor benchmark had saturated the memory bandwidth and a second processor didn't make much difference.
This was on "cheap" multi-processors.
john alvord
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