I dunno how accurate it is. Maybe it's just the number of slices
multiplied by something.
Ad.
Hayim Shaul wrote:
man clock(3) read:
"
DESCRIPTION
The clock() function returns an approximation of processor time used by
the program.
RETURN VALUE
The value returned is the CPU time used so far as a clock_t; to get the
number of seconds used, divide by CLOCKS_PER_SEC. If the processor
time used is not available or its value cannot be represented, the
function returns the value (clock_t)-1.
"
It seems to me that this is what you are looking for.
CLOCKS_PER_SEC is set to 1,000,000 on all machines I worked with.
Is this not acurate enough?
Or are you bothered by the word "approximation" in the description?
Hayim.
PS. I think it would be better to have the kernel-newbies CC-ed so
others will be able to reference these correspondence.
On Tue, 29 Nov 2005, Adrian May wrote:
Nope. I wanna know exactly how much time my process has consumed, not
including time I was scheduled out.
Ad.
Hayim Shaul wrote:
Is clock() what you mean?
On Mon, 28 Nov 2005, Adrian May wrote:
Hi folks,
I don't know whether I have to hack the kernel for this or not, but
figured you lot would know.
I want very accurate timing inside my app. That means, my process
will ask for it's exact age at various times. This age should not
include times when some other process was scheduled, but it should
include the overhead of the timing itself, which gets done by my
process. I want it to be high performance because I'll be doing it
very often indeed. Function-level profiling is not enough because I
need the time spent inside one specific function in particular, but
separated out according to a parameter to that function. (Basically
it's a VM that hosts zillions of tiny scripts and wants to keep
perfect accounts about time used by all of them and that used by
the VM itself).
I think that poking about in /proc would be too slow, but I bet the
kernel knows how many jiffies my process has had, and if I could
figure out what time (in usecs) my current slice started I could
use the usec timer to figure out how old this slice is and work out
the final answer that way. Or maybe there's a better strategy. I
need it really accurate and fast though - ideally in processor
cycles, but I somehow need to exclude the times I'm scheduled out.
Any ideas?
Thanks in advance,
Adrian.
BTW - I'll also need interval timers to terminate greedy scripts
but they don't have to be all that accurate.
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