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Old 2011-04-04, 22:35   #176
Rhyled's Avatar
May 2010

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Default Minor bugs when using #workers < #cores

I ran into a couple of less than optimum issues when running 2 workers on my 4 core i7 920 processor. (My electric bill has sent me on a frugality hunt)

i7-920 @ 3.5 GHz w/ HT
Gigabyte Mobo GA-EX58-UD3R
3x 2GB 1333 MHz DDR3
Prime95 Windows 64-bit 26.5 build 5

Smart Assignment isn't so smart:
I noticed that my iteration times were slowing down by up to 10% on an otherwise untouched system, from 17 ms to 19ms on a LL-D in the 25M range. From the looks of my Task Manager performance graphs at high speed, the task was switching between cores. Not a disaster, but when changed the cpu assignments to a fixed core (5 & 7), the iterations dropped back to a consistent 17 ms. My guess is the L2 cache was getting dumped during core switches, slowing things down a touch.

CPUS are numbered differently in Worker Window and Status window:
When editing the Worker Window assignments, CPUs are numbered 1-8. In the status window, they are numbered 0-7. E.g. My worker #1 assigned to CPU #5 is described as affinity set to logical CPU #4 and #7 shows up as #6. No biggie, just slightly confusing.
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