Date: Tue, 13 Jun 2006 11:43:36 -0700 (PDT) From: Danial Thom <danial_thom@yahoo.com> To: Robert Watson <rwatson@FreeBSD.org> Cc: freebsd-performance@freebsd.org, David Xu <davidxu@freebsd.org> Subject: Re: Initial 6.1 questions Message-ID: <20060613184336.60229.qmail@web33314.mail.mud.yahoo.com> In-Reply-To: <20060613193040.O26068@fledge.watson.org>
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--- Robert Watson <rwatson@FreeBSD.org> wrote:
>
> On Tue, 13 Jun 2006, Danial Thom wrote:
>
> > Maybe someone can explain this output. The
> top line shows 99.6%idle. Is it
> > just showing CPU 0s stats on the top line?
>
> Two types of measurements are taken: sampled
> ticks regarding whether the
> system as a while is in {user, nice, system,
> intr, idle}, and then sampling
> for individual processes. Right now, the
> system measurements are kept in a
> simple array of tick counters called cp_time.
> John Baldwin and others have
> changes that make these tick counters per-CPU.
> The lines at the top of
> top(1)'s output are derived from those tick
> counters. Ticks are measured on
> each CPU, so those are a summary across all
> CPUs. To add cpustat support, we
> need to merge John's patch to make cp_time
> per-CPU (ie., different counters
> for different CPUs) and teach the userland
> tools to retrieve them. When you
> run top you'll notice that it adjusts the
> measurements each refresh. In
> effect, what it's doing is sampling the change
> in tick counts over the window,
> pulling down the new values and calculating the
> percentages of ticks in each
> "bucket" in the last window.
That doesn't explain why the Top line shows 99.6%
idle, but the cpu idle threads are showing
significant usage.
I'm getting a constant 6000 Interrupts / Second
on my em controller, yet top jumps all over the
place; sitting at 99% idle for 10 seconds, then
jumping to 50%, then somewhere in between. It
seems completely unreliable. The load I'm
applying is constant.
DT
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