Hi Corey, Linus,
On Wednesday 03 March 2010 05:14:38 pm Corey Minyard wrote:
> From: Martin Wilck <[email protected]>
>
> 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 <[email protected]>
> Cc: Jean Delvare <[email protected]>
> Signed-off-by: Corey Minyard <[email protected]>
> ---
> This patch has been discussed quite a bit, and I believe all issues with it
> have been resolved. It's not great, but nobody has a better way to handle
> the problem.
I still can't see this patch in Linus' tree as of 2.6.34-rc1. It has been
waiting for sooo long already, can we finally get it in? Linus, will you apply
it? Or should it go through Andrew?
Thanks.
> Index: linux-2.6.32/drivers/char/ipmi/ipmi_si_intf.c
> ===================================================================
> --- linux-2.6.32.orig/drivers/char/ipmi/ipmi_si_intf.c
> +++ linux-2.6.32/drivers/char/ipmi/ipmi_si_intf.c
> @@ -294,6 +294,9 @@ 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);
> @@ -924,23 +927,77 @@ static void set_run_to_completion(void *
> }
> }
>
> +/*
> + * 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;
> }
> @@ -1211,6 +1268,11 @@ 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)
> Index: linux-2.6.32/Documentation/IPMI.txt
> ===================================================================
> --- linux-2.6.32.orig/Documentation/IPMI.txt
> +++ linux-2.6.32/Documentation/IPMI.txt
> @@ -365,6 +365,7 @@ You can change this at module load time
> 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 for
> 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
--
Jean Delvare
Suse L3
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