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authorMartin Wilck <martin.wilck@ts.fujitsu.com>2010-03-10 15:23:06 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-12 15:52:39 -0800
commitae74e823cb7d4cd476f623fce9a38f625f6c09a8 (patch)
tree404aba91d5c634cfc8d3ecc847281f12fc8e5e1e /Documentation/IPMI.txt
parentf1eb1332b8f07e937add24c6fd2ac40b8737a2f4 (diff)
downloadlinux-ae74e823cb7d4cd476f623fce9a38f625f6c09a8.tar.gz
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 <martin.wilck@ts.fujitsu.com> Signed-off-by: Corey Minyard <cminyard@mvista.com> Cc: Jean Delvare <jdelvare@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/IPMI.txt')
-rw-r--r--Documentation/IPMI.txt12
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/IPMI.txt b/Documentation/IPMI.txt
index bc38283379f..69dd29ed824 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=<shift1>,<shift2>,...
slave_addrs=<addr1>,<addr2>,...
force_kipmid=<enable1>,<enable2>,...
+ kipmid_max_busy_us=<ustime1>,<ustime2>,...
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=<shift1>,<shift2>,...
ipmi_si.slave_addrs=<addr1>,<addr2>,...
ipmi_si.force_kipmid=<enable1>,<enable2>,...
+ ipmi_si.kipmid_max_busy_us=<ustime1>,<ustime2>,...
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