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From: John Baldwin <jhb@FreeBSD.org>
To: Alfred Perlstein <alfred@FreeBSD.org>
Date: Mon, 1 Nov 2004 14:41:33 -0500
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	<20041101045331.GP16728@cs.rice.edu> <20041101105113.GS24892@elvis.mu.org>
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cc: Alan Cox <alc@FreeBSD.org>
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cc: Alan Cox <alc@cs.rice.edu>
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Subject: Re: cvs commit: src/sys/vm vm_zeroidle.c
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On Monday 01 November 2004 05:51 am, Alfred Perlstein wrote:
> * Alan Cox <alc@cs.rice.edu> [041031 20:53] wrote:
> > On Sun, Oct 31, 2004 at 07:13:17PM -0800, Alfred Perlstein wrote:
> > > * Alan Cox <alc@FreeBSD.org> [041031 11:33] wrote:
> > > > alc         2004-10-31 19:32:57 UTC
> > > >
> > > >   FreeBSD src repository
> > > >
> > > >   Modified files:
> > > >     sys/vm               vm_zeroidle.c
> > > >   Log:
> > > >   Introduce a Boolean variable wakeup_needed to avoid repeated,
> > > > unnecessary calls to wakeup() by vm_page_zero_idle_wakeup().
> > > >
> > > >   Revision  Changes    Path
> > > >   1.31      +9 -2      src/sys/vm/vm_zeroidle.c
> > >
> > > Why not switch to a cv?
> >
> > Calling cv_signal repeatedly would be no better than calling wakeup()
> > repeatedly.  Either way, a Boolean variable is desirable to prevent
> > unnecessary calls.
>
> Yah, I figured there would be something in the cv code to optimize
> the "no waiters" case.

There is, though sometimes it might think there are waiters when there 
actually aren't any.

-- 
John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org