Danial Thom wrote:
--- Scott Long <[EMAIL PROTECTED]> wrote:
Danial Thom wrote:
--- Robert Watson <[EMAIL PROTECTED]>
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
Be aware that there was a significant change
made to if_em
in 7-CURRENT in Jan 2006 to improve load
performance. It'll
probably get backported for 6.2, but you might
consider
looking at it before you make up your mind on
6.1 performance.
I can bridge 1 million pps with the em driver in
4.9, and it looks pretty much intact in 6.1, so
I'm not too worried about the em driver being the
problem here. Plus the measurements look just
fine with 1 cpu, and they are completely
impossible in SMP mode. So its reasonable to
conclude that the measurement tools simply don't
work.
Since everyone agrees that the load measuring
tools aren't all that accurate, what criteria was
used to determine that the changes made in 7 have
the effect that you think they have had?
DT
DT
It was tested with a Smartbits packet generator. The
tx rate on the generator was increased in steps until the host
started dropping packets or became otherwise unresponsive.
Scott
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