Re: Dynticks Causing High Context Switch Rate in ksoftirqd

On Mon, 26 Nov 2007 22:36:17 -0600 Robert Hancock <hancockr@xxxxxxx> wrote:

bdupree@xxxxxxxxxxxxxxx wrote:
Question: Why is ksoftirqd eating about 5 to 10 percent of my CPU on an idle
system? The problem occurs if I config the kernel with tickless
support (i.e. CONFIG_TICK_ONESHOT=y). (Thanks to "oprofile" for putting me
onto this.)

I have noted this same problem on kernel versions: 2.6.23.1, 2.6.23.8 and
2.6.23.9

**************************************************************************
*** Output from "vmstat -n 1 10" -- Note very high context switch rate ***
*** This is on a idle machine! ***
**************************************************************************

procs -----------memory---------- ---swap-- -----io---- --system--
----cpu----
r b swpd free buff cache si so bi bo in cs us sy
id wa
0 0 0 1925556 4768 116104 0 0 124 2 6 7538 1 2
96 1
0 0 0 1925556 4768 116104 0 0 0 0 2 147329 0 1
99 0

What did oprofile show? It should be able to narrow down what
function(s) are responsible for the CPU usage..

Sigh. I just asked a similar thing. Let's look at the mail headers:



Message-ID: <41877.67.173.156.207.1196130992.squirrel@xxxxxxxxxxxxxxxxxxx>
...
From: bdupree@xxxxxxxxxxxxxxx


From: Robert Hancock <hancockr@xxxxxxx>
...
In-reply-to: <fa.c70Wy8WHP3DOaDydQ2D94+Xxx/8@xxxxxxxxxx>


Please fix your email client so as to not break threading?
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