Re: [PATCH] vhost: Add polling mode

On Sun, Aug 17, 2014 at 03:35:39PM +0300, Razya Ladelsky wrote:

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Hi Michael,

Sorry for the delay, had some problems with my mailbox, and I realized 

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just now that 
my reply wasn't sent.
The vm indeed ALWAYS utilized 100% cpu, whether polling was enabled or 

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not.
The vhost thread utilized less than 100% (of the other cpu) when 

polling 

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was disabled.
Enabling polling increased its utilization to 100% (in which case both 

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cpus were 100% utilized). 

Hmm this means the testing wasn't successful then, as you said:

   The idea was to get it 100% loaded, so we can see that the polling is
   getting it to produce higher throughput.

in fact here you are producing more throughput but spending more power
to produce it, which can have any number of explanations besides polling
improving the efficiency. For example, increasing system load might
disable host power management.

Hi Michael,
I re-ran the tests, this time with the  "turbo mode" and  "C-states" 
features off.
No Polling:
1 VM running netperf (msg size 64B): 1107 Mbits/sec
 Polling:
1 VM running netperf (msg size 64B): 1572 Mbits/sec







As you can see from the new results, the numbers are lower, 
but relatively (polling on/off) there's no change.
Thank you,
Razya

That was just one example. There many other possibilities.  Either
actually make the systems load all host CPUs equally, or divide
throughput by host CPU.

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MST

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