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SubjectRe: gettimeofday() vs. /proc/rtc

On Sun, 19 Jul 1998, Richard B. Johnson wrote:

> How would you get a system call from user mode to take less than 1
> microsecond, is really what you are asking. [...]

actually, if you look at the SYSENTER/SYSEXIT patch and testcode posted
recently, with that stuff a PII does a getpid() in ~150 cycles. This means
a 0.5 microseconds system call on a 300MHz PII, 0.33 microseconds on a
450MHz PII. So Intel has indeed fixed the latency of system entry.

with that stuff, gettimeofday() takes ~300 cycles, thats under 1
microsecond too. (unless you have CONFIG_APM turned on, but people have
posted patches to fix that case too)

-- mingo


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