On 11/07/2012 03:51 AM, Andrew Morton wrote:
> On Tue, 6 Nov 2012 21:09:58 +0800
> Alex Shi <alex....@intel.com> wrote:
>
>> $for ((i=0; i < I; i++)) ; do while true; do : ; done & done
>>
>> Checking the power consuming with a powermeter on the NHM EP.
>> powersaving performance
>> I = 2 148w 160w
>> I = 4 175w 181w
>> I = 8 207w 224w
>> I = 16 324w 324w
>>
>> On a SNB laptop(4 cores *HT)
>> powersaving performance
>> I = 2 28w 35w
>> I = 4 38w 52w
>> I = 6 44w 54w
>> I = 8 56w 56w
>>
>> On the SNB EP machine, when I = 16, power saved more than 100 Watts.
>
> Confused. According to the above table, at I=16 the EP machine saved 0
> watts. Typo in the data?
Not typo, since the LCPU number in the EP machine is 16, so if I = 16,
the powersaving policy doesn't work actually. That is the patch designed
for race to idle assumption.
The result looks same as the third patch(for fork/exec/wu) applied.
Result put here because it is from this patch.
>
>
> Also, that's a pretty narrow test - it's doing fork and exec at very
> high frequency and things such as task placement decisions at process
> startup might be affecting the results. Also, the load will be quite
> kernel-intensive, as opposed to the more typical userspace-intensive
> loads.
Sorry, why you think it keep do fork/exec? It just generate several
'bash' task to burn CPU, without fork/exec.
with I = 8, on my 32 LCPU SNB EP machine:
No do_fork calling in 5 seconds.
$ sudo perf stat -e probe:* -a sleep 5
Performance counter stats for 'sleep 5':
3 probe:do_execve [100.00%]
0 probe:do_fork [100.00%]
And it is not kernel-intensive, it nearly running all in user level.
'Top' output: 25:0%us VS 0.0%sy
Tasks: 319 total, 9 running, 310 sleeping, 0 stopped, 0 zombie
Cpu(s): 25.0%us, 0.0%sy, 0.0%ni, 74.5%id, 0.4%wa, 0.1%hi, 0.0%si,
0.0%st
...
> So, please run a broader set of tests so we can see the effects?
>
Really, I have no more ideas for the suitable benchmarks.
Just tried the kbuild -j 16 on the 32 LCPU SNB EP, power just saved 10%,
but compile time increase about ~15%.
Seems if the task number is variation around the powersaving criteria
number, that just cause trouble.
--
Thanks
Alex
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