Date: Fri, 21 Mar 2008 15:36:24 -0700 (PDT) From: Barney Cordoba <barney_cordoba@yahoo.com> To: Julian Elischer <julian@elischer.org> Cc: current@freebsd.org Subject: Re: kvm_read() vs ioctl performance Message-ID: <817070.5892.qm@web63911.mail.re1.yahoo.com> In-Reply-To: <47E40196.6060703@elischer.org>
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--- Julian Elischer <julian@elischer.org> wrote:
> Barney Cordoba wrote:
> > I have an app which reads stats from the kernel
> > periodically, and there can be a lot of
> iterations,
> > sometimes 20,000 or more. I'm thinking of
> converting
> > from an ioctl method to kvm_read(). KVM is
> certainly
> > simpler, but its not clear what overhead is
> involved,
> > since kvm_read() likely has to call the kernel
> also.
> >
> > Does anyone have a handle on the difference in
> > overhead, assuming that the ioctl call is to a
> module
> > which does nothing more than copy the data and
> return?
>
> tried a shared memory page?
No, but I built a test and kvm_read is 70 times
faster, in
case anyone is interested.
Barney
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