From: Richard Hirst <rhirst@linuxcare.com>
To: Matthew Wilcox <willy@debian.org>
Cc: Carlos O'Donell <carlos@baldric.uwo.ca>,
Grant Grundler <grundler@parisc-linux.org>,
parisc-linux@parisc-linux.org
Subject: Re: [parisc-linux] Generic light-weight syscall.
Date: Mon, 28 Jul 2003 22:10:12 +0100 [thread overview]
Message-ID: <20030728211012.GC6706@sleepie.demon.co.uk> (raw)
In-Reply-To: <20030728191420.GE3840@parcelfarce.linux.theplanet.co.uk>
On Mon, Jul 28, 2003 at 08:14:20PM +0100, Matthew Wilcox wrote:
> On Mon, Jul 28, 2003 at 03:04:55PM -0400, Carlos O'Donell wrote:
> > > You know, you don't even need kernel help for this. According to page
> > > 2-5 of the Kane book, the Interval Timer is accessible by non-privileged
> > > instructions.
> >
> > Isn't this going to be different for all CPU's? Which means if you get
> > scheduled around you might see negative moving time?
>
> We discussed this in the Black Thorn ... record what value you last
> returned to the user and never return less than that.
Not very nice if the difference between CPUs is significant. You could
find yourself checking time on CPU A, doing some work, getting moved to
CPU B, checking time, and finding you apparently did all that in 0ns.
Richard
next prev parent reply other threads:[~2003-07-28 21:10 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-25 6:37 [parisc-linux] Generic light-weight syscall Carlos O'Donell
2003-07-25 11:37 ` Matthew Wilcox
2003-07-26 17:48 ` Carlos O'Donell
2003-07-26 18:00 ` Carlos O'Donell
2003-07-27 12:27 ` Grant Grundler
2003-07-28 15:57 ` Carlos O'Donell
2003-07-28 17:45 ` Matthew Wilcox
2003-07-28 19:04 ` Carlos O'Donell
2003-07-28 19:14 ` Matthew Wilcox
2003-07-28 21:10 ` Richard Hirst [this message]
2003-07-29 17:50 ` Carlos O'Donell
2003-07-29 18:55 ` Grant Grundler
2003-07-29 21:06 ` Richard Hirst
2003-07-29 23:36 ` Carlos O'Donell
2003-07-30 16:37 ` Thibaut VARENE
2003-07-29 23:38 ` Carlos O'Donell
2003-07-29 18:51 ` Grant Grundler
2003-07-27 20:43 ` Michael S.Zick
2003-07-28 20:30 ` Randolph Chung
2003-07-28 20:37 ` Matthew Wilcox
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