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Subject[PATCH] limit CPU time spent in kipmid (version 4)
Hi all,

I am sorry for the long silence. I am sending here a new version of my
patch which takes into account Bela's suggestions (well, most of them).
I compiled and tested it with 2.6.29.4, the results are similar as
before. 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.

Please give me some feedback whether this patch will get merged, and if
not, what improvement is needed.

Regards
Martin

--
Dr. Martin Wilck
PRIMERGY System Software Engineer
x86 Server Engineering

Fujitsu Technology Solutions GmbH
Heinz-Nixdorf-Ring 1
33106 Paderborn, Germany

Phone: ++49 5251 525 2796
Fax: ++49 5251 525 2820
Email: martin.wilck@ts.fujitsu.com
Internet: http://ts.fujitsu.com
Company Details: http://de.ts.fujitsu.com/imprint.html
Signed-off-by: martin.wilck@ts.fujitsu.com
--- linux-2.6.29.4/drivers/char/ipmi/ipmi_si_intf.c 2009-05-19 01:52:34.000000000 +0200
+++ linux-2.6.29-rc8/drivers/char/ipmi/ipmi_si_intf.c 2009-06-04 15:30:34.855398091 +0200
@@ -297,6 +297,9 @@
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);
@@ -927,23 +930,56 @@
}
}

+#define ipmi_si_set_not_busy(timespec) \
+ do { (timespec)->tv_nsec = -1; } while (0)
+#define ipmi_si_is_busy(timespec) ((timespec)->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;
+}
+
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;
}
@@ -1213,6 +1249,11 @@
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)
\
 
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