Re: Time spent in user mode and system mode.
Cyril Roelandt, le Tue 23 Oct 2012 22:07:19 +0200, a écrit :
> On 10/19/2012 02:54 PM, Samuel Thibault wrote:
> >Cyril Roelandt, le Fri 19 Oct 2012 00:42:12 +0200, a écrit :
> >>On GNU/Linux, sysconf(_SC_CLK_TCK_) returns 100, so the time spent in user
> >>mode would be 2884 ticks (if we use the values from my example), which is
> >>2884/100 = 28.84 seconds.On Hurd, sysconf(_SC_CLK_TCK) returns 1000000, so,
> >>does that mean that the time spent in user mode is roughly zero ?
> >
> >No, because of this:
> >
> >>On my machine, /hurd/procfs is launched with the "-c" option (Linux
> >>compatible) which forces the translator to use 100 as the number of ticks
> >>per second, rather than calling sysconf(_SC_CLK_TCK_). But one just cannot
> >>easily retrieve this value. I must admit I'm a bit confused.
> >
> >The problem we have is that a lot of tools don't call
> >sysconf(_SC_CLK_TCK_), but actually hardcode 100. That is why a
> >compatibility mode was introduced for them, but it's independent from
> >the _SC_CLK_TCK value, thus the confusion. Ideally we fix all users of
> >/proc which hardcode 100, and then we can get rid of the -c option.
>
> So, would calling sysconf(_SC_CLK_TCK_) rather than using "100" result in
> getting wrong values ? :-p
Unfortunately currently yes.
Samuel
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