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Re: [address@hidden: [PATCH] Make __getclktck return 100 for the Hurd]
From: |
Roland McGrath |
Subject: |
Re: [address@hidden: [PATCH] Make __getclktck return 100 for the Hurd] |
Date: |
Tue, 11 Jun 2013 16:13:53 -0700 (PDT) |
> Basically, top doesn't report correct CPU times. This is caused by
> sysconf() returning 1000000 while values read from /proc are true tick
> counts, hence 100 per second at most.
In fact, that is not a "true tick count". Most modern Linux kernels have
ticks at 1024Hz, for example. The ABI for certain /proc/PID/* files is
that certain fields are in centiseconds. That has nothing (except for an
historical relationship) to do with the actual frequency used in the kernel.
This is a bug in procfs, regardless. If it's a good idea to change what
libc uses, then we'll change. Any caller of times or clock (i.e. any
interface using clock_t) has to use sysconf (_SC_CLK_TCK) to know the
translation from "clock ticks" to units of real time.