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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.arch
Subject: Re: Cost of handling misaligned access
Date: Fri, 7 Feb 2025 12:41:38 +0200
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On Fri, 7 Feb 2025 11:06:43 +0100
Terje Mathisen <terje.mathisen@tmsw.no> wrote:

> Michael S wrote:
> > On Thu, 6 Feb 2025 21:36:38 +0100
> > Terje Mathisen <terje.mathisen@tmsw.no> wrote:  
> >> BTW, when I timed 1000 calls to that 5-6 us program, to get around
> >> teh 100 ns timer resolution, each iteration ran in 5.23 us.  
> > 
> > That measurement could be good enough on desktop. Or not.
> > It certainly not good enough on laptop and even less so on server.
> > On laptop I wouldn't be sutisfied before I lok my program to
> > particualr core, then do something like 21 measurements with 100K
> > calls in each measurement (~10 sec total) and report median of 21.  
> 
> Each measurement did 1000 calls, then I ran 100 such measurements.
> The 5.23 us value was the lowest seen among the 100, with average a
> bit more:
> 
> 
> Slowest: 9205200 ns
> Fastest: 5247500 ns
> Average: 5672529 ns/iter
> Part1 = 3338
> 
> My own (old, but somewhat kept up to date) cputype program reported
> that it is a "13th Gen Intel(R) Core(TM) i7-1365U" according to CPUID.
> 
> Is that sufficient to judge the performance?
> 
> Terje
> 

Not really.
i7-1365U is a complicated beast. 2 "big" cores, 8 "medium" cores.
Frequency varies ALOT, 1.8 to 5.2 GHz on "big", 1.3 to 3.9 GHz on
"medium".
As I said above, on such CPU I wouldn't believe the numbers before
total duration of test is 10 seconds and the test run is locked to
particular core. As to 5 msec per measurement, that's enough, but why
not do longer measurements if you have to run for 10 sec anyway?