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From
SubjectRe: [PATCH][2.4.20-pre5] non syscall gettimeofday
Date
Followup to:  <1031267553.10830.71.camel@dell_ss3.pdx.osdl.net>
By author: Stephen Hemminger <shemminger@osdl.org>
In newsgroup: linux.dev.kernel
>
> The following patch implements a shared memory interface to allow
> implementing gettimeofday (and other clock measurement) using the TSC
> counter on i386. On a 1.6G Xeon this reduces gettimeofday from 1.2 us
> per call to .17 us per call.
>

This sounds like a vsyscall. Since we have discussed vsyscalls on and
off without getting anywhere, I'd like to know how your implementation
does it -- the #1 proposal I think was to map in a page at 0xfffff000
and have the vsyscall code there.

Note that the vsyscall needs to bounce to a regular syscall if TSC
time/gettimeofday aren't available.

-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com>
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