RTAS event scan has to run across all cpus. Right now we use a kernel
thread and set_cpus_allowed but in doing so we wake up the previous cpu
unnecessarily.
Some ftrace output shows this:
previous cpu (2):
[002] 7.022331: sched_switch: task swapper:0 [140] ==> rtasd:194 [120]
[002] 7.022338: sched_switch: task rtasd:194 [120] ==> migration/2:9 [0]
[002] 7.022344: sched_switch: task migration/2:9 [0] ==> swapper:0 [140]
next cpu (3):
[003] 7.022345: sched_switch: task swapper:0 [140] ==> rtasd:194 [120]
[003] 7.022371: sched_switch: task rtasd:194 [120] ==> swapper:0 [140]
We can use schedule_delayed_work_on and avoid the unnecessary wakeup.
Signed-off-by: Anton Blanchard <an...@samba.org>
---
Index: linux-2.6/arch/powerpc/platforms/pseries/rtasd.c
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/pseries/rtasd.c 2009-03-15
17:03:45.000000000 +1100
+++ linux-2.6/arch/powerpc/platforms/pseries/rtasd.c 2009-05-26
16:02:39.000000000 +1000
@@ -19,7 +19,7 @@
#include <linux/vmalloc.h>
#include <linux/spinlock.h>
#include <linux/cpu.h>
-#include <linux/delay.h>
+#include <linux/workqueue.h>
#include <asm/uaccess.h>
#include <asm/io.h>
@@ -387,36 +387,51 @@
} while(error == 0);
}
-static void do_event_scan_all_cpus(long delay)
+static void rtas_event_scan(struct work_struct *w);
+DECLARE_DELAYED_WORK(event_scan_work, rtas_event_scan);
+
+/*
+ * Delay should be at least one second since some machines have problems if
+ * we call event-scan too quickly.
+ */
+static unsigned long event_scan_delay = 1*HZ;
+static int first_pass = 1;
+
+static void rtas_event_scan(struct work_struct *w)
{
- int cpu;
+ unsigned int cpu;
+
+ do_event_scan();
get_online_cpus();
- cpu = first_cpu(cpu_online_map);
- for (;;) {
- set_cpus_allowed(current, cpumask_of_cpu(cpu));
- do_event_scan();
- set_cpus_allowed(current, CPU_MASK_ALL);
-
- /* Drop hotplug lock, and sleep for the specified delay */
- put_online_cpus();
- msleep_interruptible(delay);
- get_online_cpus();
- cpu = next_cpu(cpu, cpu_online_map);
- if (cpu == NR_CPUS)
- break;
+ cpu = next_cpu(smp_processor_id(), cpu_online_map);
+ if (cpu == NR_CPUS) {
+ cpu = first_cpu(cpu_online_map);
+
+ if (first_pass) {
+ first_pass = 0;
+ event_scan_delay = 30*HZ/rtas_event_scan_rate;
+
+ if (surveillance_timeout != -1) {
+ pr_debug("rtasd: enabling surveillance\n");
+ enable_surveillance(surveillance_timeout);
+ pr_debug("rtasd: surveillance enabled\n");
+ }
+ }
}
+
+ schedule_delayed_work_on(cpu, &event_scan_work,
+ __round_jiffies_relative(event_scan_delay, cpu));
+
put_online_cpus();
}
-static int rtasd(void *unused)
+static void start_event_scan(void)
{
unsigned int err_type;
int rc;
- daemonize("rtasd");
-
printk(KERN_DEBUG "RTAS daemon started\n");
pr_debug("rtasd: will sleep for %d milliseconds\n",
(30000 / rtas_event_scan_rate));
@@ -434,22 +449,8 @@
}
}
- /* First pass. */
- do_event_scan_all_cpus(1000);
-
- if (surveillance_timeout != -1) {
- pr_debug("rtasd: enabling surveillance\n");
- enable_surveillance(surveillance_timeout);
- pr_debug("rtasd: surveillance enabled\n");
- }
-
- /* Delay should be at least one second since some
- * machines have problems if we call event-scan too
- * quickly. */
- for (;;)
- do_event_scan_all_cpus(30000/rtas_event_scan_rate);
-
- return -EINVAL;
+ schedule_delayed_work_on(first_cpu(cpu_online_map), &event_scan_work,
+ event_scan_delay);
}
static int __init rtas_init(void)
@@ -487,8 +488,7 @@
if (!entry)
printk(KERN_ERR "Failed to create error_log proc entry\n");
- if (kernel_thread(rtasd, NULL, CLONE_FS) < 0)
- printk(KERN_ERR "Failed to start RTAS daemon\n");
+ start_event_scan();
return 0;
}
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