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ipmi: add parameter to limit CPU usage in kipmid

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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>
This commit is contained in:
Martin Wilck
2010-03-10 15:23:06 -08:00
committed by Linus Torvalds
parent f1eb1332b8
commit ae74e823cb
2 changed files with 76 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/char/ipmi/ipmi_si_intf.c
+64 -2
View File
@@ -295,6 +295,9 @@ struct smi_info {
static int force_kipmid[SI_MAX_PARMS];
static int num_force_kipmid;
static unsigned int kipmid_max_busy_us[SI_MAX_PARMS];
static int num_max_busy_us;
static int unload_when_empty = 1;
static int try_smi_init(struct smi_info *smi);
@@ -925,23 +928,77 @@ static void set_run_to_completion(void *send_info, int i_run_to_completion)
}
}
/*
* Use -1 in the nsec value of the busy waiting timespec to tell that
* we are spinning in kipmid looking for something and not delaying
* between checks
*/
static inline void ipmi_si_set_not_busy(struct timespec *ts)
{
ts->tv_nsec = -1;
}
static inline int ipmi_si_is_busy(struct timespec *ts)
{
return ts->tv_nsec != -1;
}
static int ipmi_thread_busy_wait(enum si_sm_result smi_result,
const struct smi_info *smi_info,
struct timespec *busy_until)
{
unsigned int max_busy_us = 0;
if (smi_info->intf_num < num_max_busy_us)
max_busy_us = kipmid_max_busy_us[smi_info->intf_num];
if (max_busy_us == 0 || smi_result != SI_SM_CALL_WITH_DELAY)
ipmi_si_set_not_busy(busy_until);
else if (!ipmi_si_is_busy(busy_until)) {
getnstimeofday(busy_until);
timespec_add_ns(busy_until, max_busy_us*NSEC_PER_USEC);
} else {
struct timespec now;
getnstimeofday(&now);
if (unlikely(timespec_compare(&now, busy_until) > 0)) {
ipmi_si_set_not_busy(busy_until);
return 0;
}
}
return 1;
}
/*
* A busy-waiting loop for speeding up IPMI operation.
*
* Lousy hardware makes this hard. This is only enabled for systems
* that are not BT and do not have interrupts. It starts spinning
* when an operation is complete or until max_busy tells it to stop
* (if that is enabled). See the paragraph on kimid_max_busy_us in
* Documentation/IPMI.txt for details.
*/
static int ipmi_thread(void *data)
{
struct smi_info *smi_info = data;
unsigned long flags;
enum si_sm_result smi_result;
struct timespec busy_until;
ipmi_si_set_not_busy(&busy_until);
set_user_nice(current, 19);
while (!kthread_should_stop()) {
int busy_wait;
spin_lock_irqsave(&(smi_info->si_lock), flags);
smi_result = smi_event_handler(smi_info, 0);
spin_unlock_irqrestore(&(smi_info->si_lock), flags);
busy_wait = ipmi_thread_busy_wait(smi_result, smi_info,
&busy_until);
if (smi_result == SI_SM_CALL_WITHOUT_DELAY)
; /* do nothing */
else if (smi_result == SI_SM_CALL_WITH_DELAY)
else if (smi_result == SI_SM_CALL_WITH_DELAY && busy_wait)
schedule();
else
schedule_timeout_interruptible(1);
schedule_timeout_interruptible(0);
}
return 0;
}
@@ -1212,6 +1269,11 @@ module_param(unload_when_empty, int, 0);
MODULE_PARM_DESC(unload_when_empty, "Unload the module if no interfaces are"
" specified or found, default is 1. Setting to 0"
" is useful for hot add of devices using hotmod.");
module_param_array(kipmid_max_busy_us, uint, &num_max_busy_us, 0644);
MODULE_PARM_DESC(kipmid_max_busy_us,
"Max time (in microseconds) to busy-wait for IPMI data before"
" sleeping. 0 (default) means to wait forever. Set to 100-500"
" if kipmid is using up a lot of CPU time.");
static void std_irq_cleanup(struct smi_info *info)