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| author | Martin Wilck <martin.wilck@ts.fujitsu.com> | 2010-03-10 15:23:06 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-03-12 15:52:39 -0800 |
| commit | ae74e823cb7d4cd476f623fce9a38f625f6c09a8 (patch) | |
| tree | 404aba91d5c634cfc8d3ecc847281f12fc8e5e1e /Documentation/IPMI.txt | |
| parent | f1eb1332b8f07e937add24c6fd2ac40b8737a2f4 (diff) | |
| download | lwn-ae74e823cb7d4cd476f623fce9a38f625f6c09a8.tar.gz lwn-ae74e823cb7d4cd476f623fce9a38f625f6c09a8.zip | |
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.txt | 12 |
1 files changed, 12 insertions, 0 deletions
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=<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 |