From ae74e823cb7d4cd476f623fce9a38f625f6c09a8 Mon Sep 17 00:00:00 2001 From: Martin Wilck Date: Wed, 10 Mar 2010 15:23:06 -0800 Subject: ipmi: add parameter to limit CPU usage in kipmid In some cases kipmid can use a lot of CPU. This adds a way to tune the CPU used by kipmid to help in those cases. By setting kipmid_max_busy_us to a value between 100 and 500, it is possible to bring down kipmid CPU load to practically 0 without loosing too much ipmi throughput performance. Not setting the value, or setting the value to zero, operation is unaffected. Signed-off-by: Martin Wilck Signed-off-by: Corey Minyard Cc: Jean Delvare Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/IPMI.txt | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'Documentation/IPMI.txt') diff --git a/Documentation/IPMI.txt b/Documentation/IPMI.txt index bc38283379f0..69dd29ed824e 100644 --- a/Documentation/IPMI.txt +++ b/Documentation/IPMI.txt @@ -365,6 +365,7 @@ You can change this at module load time (for a module) with: regshifts=,,... slave_addrs=,,... force_kipmid=,,... + kipmid_max_busy_us=,,... unload_when_empty=[0|1] Each of these except si_trydefaults is a list, the first item for the @@ -433,6 +434,7 @@ kernel command line as: ipmi_si.regshifts=,,... ipmi_si.slave_addrs=,,... ipmi_si.force_kipmid=,,... + ipmi_si.kipmid_max_busy_us=,,... It works the same as the module parameters of the same names. @@ -450,6 +452,16 @@ force this thread on or off. If you force it off and don't have interrupts, the driver will run VERY slowly. Don't blame me, these interfaces suck. +Unfortunately, this thread can use a lot of CPU depending on the +interface's performance. This can waste a lot of CPU and cause +various issues with detecting idle CPU and using extra power. To +avoid this, the kipmid_max_busy_us sets the maximum amount of time, in +microseconds, that kipmid will spin before sleeping for a tick. This +value sets a balance between performance and CPU waste and needs to be +tuned to your needs. Maybe, someday, auto-tuning will be added, but +that's not a simple thing and even the auto-tuning would need to be +tuned to the user's desired performance. + The driver supports a hot add and remove of interfaces. This way, interfaces can be added or removed after the kernel is up and running. This is done using /sys/modules/ipmi_si/parameters/hotmod, which is a -- cgit v1.2.3-59-g8ed1b