On Mon, 26 Sep 2011 09:56:27 -0400, Jens Mueller <jens.k.muel...@gmx.de> wrote:
Andrei Alexandrescu wrote:
On 9/25/11 11:56 PM, Robert Jacques wrote:
>On Sun, 25 Sep 2011 23:06:01 -0400, Andrei Alexandrescu
><seewebsiteforem...@erdani.org> wrote:
>>>So, std.benchmark should
>>>[ ] Set the affinity to a single thread at start (i.e. use
>>>SetProcessAffinityMask, etc)
>>
>>I think that won't influence most measurements measurably.
>
>First, a core jump is guaranteed to, essentially, poison the cache.
>Which, at least in my eyes, invalidates that particular timing run.
Well it will be one of many runs. The questions are if (a) core
jumps are likely to happen during a benchmark run, (b) many enough
will happen to influence a 500ms time window.
500?
To me it looks as if the time window is 10ms long (line 447)?
Jens
The minimum, automatic time window is 10 ms. Given the scaling factor, the
actual time window will be between 10 ms and 100 ms. IIRC A context switch
occurs every 15 ms or less. And given that you'd be starting the time window at
a random point inside the active time slice, at the minimum (i.e. 10 ms time
window) you have a 66% chance of a switch happening.
