diff options
Diffstat (limited to 'packages/linux/linux-omap/tick-schedc-suppress-needless-timer-reprogramming.patch')
| -rw-r--r-- | packages/linux/linux-omap/tick-schedc-suppress-needless-timer-reprogramming.patch | 81 |
1 files changed, 0 insertions, 81 deletions
diff --git a/packages/linux/linux-omap/tick-schedc-suppress-needless-timer-reprogramming.patch b/packages/linux/linux-omap/tick-schedc-suppress-needless-timer-reprogramming.patch deleted file mode 100644 index c5cf4ef6ef..0000000000 --- a/packages/linux/linux-omap/tick-schedc-suppress-needless-timer-reprogramming.patch +++ /dev/null @@ -1,81 +0,0 @@ -From: "Woodruff, Richard" <r-woodruff2@ti.com> - -In my device I get many interrupts from a high speed USB device in a very -short period of time. The system spends a lot of time reprogramming the -hardware timer which is in a slower timing domain as compared to the CPU. -This results in the CPU spending a huge amount of time waiting for the -timer posting to be done. All of this reprogramming is useless as the -wake up time has not changed. - -As measured using ETM trace this drops my reprogramming penalty from -almost 60% CPU load down to 15% during high interrupt rate. I can send -traces to show this. - - -Suppress setting of duplicate timer event when timer already stopped. -Timer programming can be very costly and can result in long cpu stall/wait -times. - -[akpm@linux-foundation.org: coding-style fixes] -Signed-off-by: Richard Woodruff <r-woodruff2@ti.com> -Cc: Thomas Gleixner <tglx@linutronix.de> - -On Wed, 24 Sep 2008 18:31:29 +0200 (CEST) Thomas Gleixner <tglx@linutronix.de> wrote: - -> No, we only fall trrough into raise_softirq() when the reprogram code -> detects that the event already expired. So you change the flow :) -> -> It does also not deal with delta_jiffies >= NEXT_TIMER_MAX_DELTA :( -> -> I have a closer look on that. - -Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---- - - kernel/time/tick-sched.c | 19 +++++++++++++------ - 1 file changed, 13 insertions(+), 6 deletions(-) - -diff -puN kernel/time/tick-sched.c~tick-schedc-suppress-needless-timer-reprogramming kernel/time/tick-sched.c ---- a/kernel/time/tick-sched.c~tick-schedc-suppress-needless-timer-reprogramming -+++ a/kernel/time/tick-sched.c -@@ -282,6 +282,17 @@ void tick_nohz_stop_sched_tick(int inidl - /* Schedule the tick, if we are at least one jiffie off */ - if ((long)delta_jiffies >= 1) { - -+ /* -+ * calculate the expiry time for the next timer wheel -+ * timer -+ */ -+ expires = ktime_add_ns(last_update, tick_period.tv64 * -+ delta_jiffies); -+ -+ /* Skip reprogram of event if its not changed */ -+ if (ts->tick_stopped && ktime_equal(expires, dev->next_event)) -+ goto out2; -+ - if (delta_jiffies > 1) - cpu_set(cpu, nohz_cpu_mask); - /* -@@ -332,12 +343,7 @@ void tick_nohz_stop_sched_tick(int inidl - goto out; - } - -- /* -- * calculate the expiry time for the next timer wheel -- * timer -- */ -- expires = ktime_add_ns(last_update, tick_period.tv64 * -- delta_jiffies); -+ /* Mark expiries */ - ts->idle_expires = expires; - - if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { -@@ -356,6 +362,7 @@ void tick_nohz_stop_sched_tick(int inidl - tick_do_update_jiffies64(ktime_get()); - cpu_clear(cpu, nohz_cpu_mask); - } -+out2: - raise_softirq_irqoff(TIMER_SOFTIRQ); - out: - ts->next_jiffies = next_jiffies; -_ |