[Twisted-Python] CPU choice for big twisted server.

[glyph at divmod.com]

On 01:51 am, matusis at matusis.com wrote:
>I am running a poll reactor with Twisted 2.2 on 2.6.11 kernel.
>"top" currently shows 80-90% CPU utilization for this twistd process.
>We have not switched to epoll Twisted 2.5 yet, although we are planning 
>to.

Hi, Alec!  Nice to hear that you're using Twisted in such a demanding 
situation.
>Where should we expect a better performance: on Woodcrest 5140 with 
>bigger
>L2 or on Opteron 2216 with faster RAM access? We need to order the new 
>box
>tomorrow afternoon, so if someone could reply today, it'd be great for 
>us!

I'm only replying to this message because of your extremely short 
timeframe.  I have _no_ reliable data that I would feel comfortable 
making a decision based on, but then, either of these systems will 
likely be adequate to your purposes.  So, take all this with a grain of 
salt, and I hope you get something better.

My new MacBook - a core 2 duo with 4MB of cache - slightly (10% time 
difference) outstrips my desktop work machine - an opteron64 with 1MB of 
cache - when running the Twisted unit tests.  The Opteron is almost 8 
months old now, but the MacBook is a laptop.  I am being intentionally 
vague about the rest of the specs here to stress the anecdotal and 
unscientific nature of this knowledge :-).

However, this result doesn't surprise me, and I guess it may generalize 
to the current generation of hardware, which is to say, Intel wins.  RAM 
is important, as is raw CPU speed, but L2 cache is _the_ major 
determinant of Python's performance in all of the cross-machine 
profiling I've done.  That is to say, this experiment, and this one 
other time I think I ran some stuff on a PowerPC or a MIPS or something 
(those are different, right?).

Good luck on making the right choice here with such tight constraints!
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