From: "H. Peter Anvin" <hpa@zytor.com>
To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH][2.4.20-pre5] non syscall gettimeofday
Date: 5 Sep 2002 16:38:35 -0700 [thread overview]
Message-ID: <al8ptr$up3$1@cesium.transmeta.com> (raw)
In-Reply-To: 1031267553.10830.71.camel@dell_ss3.pdx.osdl.net
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>
next prev parent reply other threads:[~2002-09-05 23:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-05 23:12 [PATCH][2.4.20-pre5] non syscall gettimeofday Stephen Hemminger
2002-09-05 23:32 ` Alan Cox
2002-09-05 23:38 ` H. Peter Anvin [this message]
2002-09-06 1:21 ` Anton Blanchard
2002-09-07 3:29 ` Pavel Machek
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