linux-omap git: add patch to suppress needless timer reprogramming

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
new file mode 100644 (file)
index 0000000..c5cf4ef
--- /dev/null
+++ b/packages/linux/linux-omap/tick-schedc-suppress-needless-timer-reprogramming.patch
@@ -0,0 +1,81 @@
+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;
+_

diff --git a/packages/linux/linux-omap_git.bb b/packages/linux/linux-omap_git.bb
index c0ec324..e229622 100644 (file)
--- a/packages/linux/linux-omap_git.bb
+++ b/packages/linux/linux-omap_git.bb
@@ -10,7 +10,7 @@ SRCREV = "014ba70469e889ebb74516052c43fd06a419b17b"
 
 PV = "2.6.27+2.6.28-rc7+${PR}+gitr${SRCREV}"
 #PV = "2.6.27+${PR}+gitr${SRCREV}"
-PR = "r4"
+PR = "r5"
 
 SRC_URI = "git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6.git;protocol=git \
           file://defconfig"
@@ -39,6 +39,7 @@ SRC_URI_append = " \
            file://0011-DSS-Support-for-OMAP3-EVM-board.patch;patch=1 \
                   http://www.bat.org/~tomba/git/0001-DSS-OMAPFB-Check-that-var-pixclock-is-not-zero.patch;patch=1 \
            file://twl-asoc-fix-record.diff;patch=1 \
+           file://tick-schedc-suppress-needless-timer-reprogramming.patch;patch=1 \
 "