Re: [patch] sched: accurate user accounting
From: malc
Date: Sun Mar 25 2007 - 10:59:49 EST
On Mon, 26 Mar 2007, Con Kolivas wrote:
On Sunday 25 March 2007 23:06, malc wrote:
On Sun, 25 Mar 2007, Con Kolivas wrote:
On Sunday 25 March 2007 21:46, Con Kolivas wrote:
On Sunday 25 March 2007 21:34, malc wrote:
On Sun, 25 Mar 2007, Ingo Molnar wrote:
* Con Kolivas <kernel@xxxxxxxxxxx> wrote:
For an rsdl 0.33 patched kernel. Comments? Overhead worth it?
[..snip..]
---
Currently we only do cpu accounting to userspace based on what is
actually happening precisely on each tick. The accuracy of that
accounting gets progressively worse the lower HZ is. As we already keep
accounting of nanosecond resolution we can accurately track user cpu,
nice cpu and idle cpu if we move the accounting to update_cpu_clock with
a nanosecond cpu_usage_stat entry. This increases overhead slightly but
avoids the problem of tick aliasing errors making accounting unreliable.
Signed-off-by: Con Kolivas <kernel@xxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
[..snip..]
Forgot to mention. Given that this goes into the kernel, shouldn't
Documentation/cpu-load.txt be amended/removed?
Yes that's a good idea. Also there should be a sanity check because sometimes
for some reason noone's been able to explain to me sched_clock gives a value
which doesn't make sense (time appears to have gone backwards) and that will
completely ruin the accounting from then on.
After running this new kernel for a while i guess i have hit this issue:
http://www.boblycat.org/~malc/apc/bad-load.png
Top and icewm's monitor do show incredibly huge load while in reality
nothing like that is really happening. Both ad-hoc and `/proc/stat' (idle)
show normal CPU utilization (7% since i'm doing some A/V stuff in the
background)
--
vale
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