diff mbox

[3.8.y.z,extended,stable] Patch "Revert "cpuidle: Quickly notice prediction failure for repeat mode"" has been added to staging queue

Message ID 1376528725-1620-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Aug. 15, 2013, 1:05 a.m. UTC 
This is a note to let you know that I have just added a patch titled

    Revert "cpuidle: Quickly notice prediction failure for repeat mode"

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

From 20878514895695617f9a9a6de6a1188e9755437d Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Sat, 27 Jul 2013 01:41:34 +0200
Subject: Revert "cpuidle: Quickly notice prediction failure for repeat mode"

commit 148519120c6d1f19ad53349683aeae9f228b0b8d upstream.

Revert commit 69a37bea (cpuidle: Quickly notice prediction failure for
repeat mode), because it has been identified as the source of a
significant performance regression in v3.8 and later as explained by
Jeremy Eder:

  We believe we've identified a particular commit to the cpuidle code
  that seems to be impacting performance of variety of workloads.
  The simplest way to reproduce is using netperf TCP_RR test, so
  we're using that, on a pair of Sandy Bridge based servers.  We also
  have data from a large database setup where performance is also
  measurably/positively impacted, though that test data isn't easily
  share-able.

  Included below are test results from 3 test kernels:

  kernel       reverts
  -----------------------------------------------------------
  1) vanilla   upstream (no reverts)

  2) perfteam2 reverts e11538d1f03914eb92af5a1a378375c05ae8520c

  3) test      reverts 69a37beabf1f0a6705c08e879bdd5d82ff6486c4
                       e11538d1f03914eb92af5a1a378375c05ae8520c

  In summary, netperf TCP_RR numbers improve by approximately 4%
  after reverting 69a37beabf1f0a6705c08e879bdd5d82ff6486c4.  When
  69a37beabf1f0a6705c08e879bdd5d82ff6486c4 is included, C0 residency
  never seems to get above 40%.  Taking that patch out gets C0 near
  100% quite often, and performance increases.

  The below data are histograms representing the %c0 residency @
  1-second sample rates (using turbostat), while under netperf test.

  - If you look at the first 4 histograms, you can see %c0 residency
    almost entirely in the 30,40% bin.
  - The last pair, which reverts 69a37beabf1f0a6705c08e879bdd5d82ff6486c4,
    shows %c0 in the 80,90,100% bins.

  Below each kernel name are netperf TCP_RR trans/s numbers for the
  particular kernel that can be disclosed publicly, comparing the 3
  test kernels.  We ran a 4th test with the vanilla kernel where
  we've also set /dev/cpu_dma_latency=0 to show overall impact
  boosting single-threaded TCP_RR performance over 11% above
  baseline.

  3.10-rc2 vanilla RX + c0 lock (/dev/cpu_dma_latency=0):
  TCP_RR trans/s 54323.78

  -----------------------------------------------------------
  3.10-rc2 vanilla RX (no reverts)
  TCP_RR trans/s 48192.47

  Receiver %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     0]:
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    59]:
  ***********************************************************
     40.0000 -    50.0000 [     1]: *
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [     0]:

  Sender %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     0]:
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    11]: ***********
     40.0000 -    50.0000 [    49]:
  *************************************************
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [     0]:

  -----------------------------------------------------------
  3.10-rc2 perfteam2 RX (reverts commit
  e11538d1f03914eb92af5a1a378375c05ae8520c)
  TCP_RR trans/s 49698.69

  Receiver %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     1]: *
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    59]:
  ***********************************************************
     40.0000 -    50.0000 [     0]:
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [     0]:

  Sender %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     0]:
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [     2]: **
     40.0000 -    50.0000 [    58]:
  **********************************************************
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [     0]:

  -----------------------------------------------------------
  3.10-rc2 test RX (reverts 69a37beabf1f0a6705c08e879bdd5d82ff6486c4
  and e11538d1f03914eb92af5a1a378375c05ae8520c)
  TCP_RR trans/s 47766.95

  Receiver %c0
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     1]: *
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    27]: ***************************
     40.0000 -    50.0000 [     2]: **
     50.0000 -    60.0000 [     0]:
     60.0000 -    70.0000 [     2]: **
     70.0000 -    80.0000 [     0]:
     80.0000 -    90.0000 [     0]:
     90.0000 -   100.0000 [    28]: ****************************

  Sender:
      0.0000 -    10.0000 [     1]: *
     10.0000 -    20.0000 [     0]:
     20.0000 -    30.0000 [     0]:
     30.0000 -    40.0000 [    11]: ***********
     40.0000 -    50.0000 [     0]:
     50.0000 -    60.0000 [     1]: *
     60.0000 -    70.0000 [     0]:
     70.0000 -    80.0000 [     3]: ***
     80.0000 -    90.0000 [     7]: *******
     90.0000 -   100.0000 [    38]: **************************************

  These results demonstrate gaining back the tendency of the CPU to
  stay in more responsive, performant C-states (and thus yield
  measurably better performance), by reverting commit
  69a37beabf1f0a6705c08e879bdd5d82ff6486c4.

Requested-by: Jeremy Eder <jeder@redhat.com>
Tested-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
[ kamal: revert 69a37bea from 3.8 instead of upstream revert ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/cpuidle/governors/menu.c | 65 ++--------------------------------------
 include/linux/tick.h             |  6 ----
 kernel/time/tick-sched.c         |  4 ---
 3 files changed, 2 insertions(+), 73 deletions(-)

--
1.8.1.2
diff mbox

Patch

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index b69a87e..322967f 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -28,13 +28,6 @@ 
 #define MAX_INTERESTING 50000
 #define STDDEV_THRESH 400

-/* 60 * 60 > STDDEV_THRESH * INTERVALS = 400 * 8 */
-#define MAX_DEVIATION 60
-
-static DEFINE_PER_CPU(struct hrtimer, menu_hrtimer);
-static DEFINE_PER_CPU(int, hrtimer_status);
-/* menu hrtimer mode */
-enum {MENU_HRTIMER_STOP, MENU_HRTIMER_REPEAT};

 /*
  * Concepts and ideas behind the menu governor
@@ -198,30 +191,6 @@  static u64 div_round64(u64 dividend, u32 divisor)
 	return div_u64(dividend + (divisor / 2), divisor);
 }

-/* Cancel the hrtimer if it is not triggered yet */
-void menu_hrtimer_cancel(void)
-{
-	int cpu = smp_processor_id();
-	struct hrtimer *hrtmr = &per_cpu(menu_hrtimer, cpu);
-
-	/* The timer is still not time out*/
-	if (per_cpu(hrtimer_status, cpu)) {
-		hrtimer_cancel(hrtmr);
-		per_cpu(hrtimer_status, cpu) = MENU_HRTIMER_STOP;
-	}
-}
-EXPORT_SYMBOL_GPL(menu_hrtimer_cancel);
-
-/* Call back for hrtimer is triggered */
-static enum hrtimer_restart menu_hrtimer_notify(struct hrtimer *hrtimer)
-{
-	int cpu = smp_processor_id();
-
-	per_cpu(hrtimer_status, cpu) = MENU_HRTIMER_STOP;
-
-	return HRTIMER_NORESTART;
-}
-
 /*
  * Try detecting repeating patterns by keeping track of the last 8
  * intervals, and checking if the standard deviation of that set
@@ -298,9 +267,6 @@  static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	int i;
 	int multiplier;
 	struct timespec t;
-	int repeat = 0, low_predicted = 0;
-	int cpu = smp_processor_id();
-	struct hrtimer *hrtmr = &per_cpu(menu_hrtimer, cpu);

 	if (data->needs_update) {
 		menu_update(drv, dev);
@@ -335,7 +301,7 @@  static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	data->predicted_us = div_round64(data->expected_us * data->correction_factor[data->bucket],
 					 RESOLUTION * DECAY);

-	repeat = get_typical_interval(data);
+	get_typical_interval(data);

 	/*
 	 * We want to default to C1 (hlt), not to busy polling
@@ -356,10 +322,8 @@  static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)

 		if (s->disabled || su->disable)
 			continue;
-		if (s->target_residency > data->predicted_us) {
-			low_predicted = 1;
+		if (s->target_residency > data->predicted_us)
 			continue;
-		}
 		if (s->exit_latency > latency_req)
 			continue;
 		if (s->exit_latency * multiplier > data->predicted_us)
@@ -369,28 +333,6 @@  static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 		data->exit_us = s->exit_latency;
 	}

-	/* not deepest C-state chosen for low predicted residency */
-	if (low_predicted) {
-		unsigned int timer_us = 0;
-
-		/*
-		 * Set a timer to detect whether this sleep is much
-		 * longer than repeat mode predicted.  If the timer
-		 * triggers, the code will evaluate whether to put
-		 * the CPU into a deeper C-state.
-		 * The timer is cancelled on CPU wakeup.
-		 */
-		timer_us = 2 * (data->predicted_us + MAX_DEVIATION);
-
-		if (repeat && (4 * timer_us < data->expected_us)) {
-			RCU_NONIDLE(hrtimer_start(hrtmr,
-				ns_to_ktime(1000 * timer_us),
-				HRTIMER_MODE_REL_PINNED));
-			/* In repeat case, menu hrtimer is started */
-			per_cpu(hrtimer_status, cpu) = MENU_HRTIMER_REPEAT;
-		}
-	}
-
 	return data->last_state_idx;
 }

@@ -481,9 +423,6 @@  static int menu_enable_device(struct cpuidle_driver *drv,
 				struct cpuidle_device *dev)
 {
 	struct menu_device *data = &per_cpu(menu_devices, dev->cpu);
-	struct hrtimer *t = &per_cpu(menu_hrtimer, dev->cpu);
-	hrtimer_init(t, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
-	t->function = menu_hrtimer_notify;

 	memset(data, 0, sizeof(struct menu_device));

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 1a6567b..f37fceb 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -142,10 +142,4 @@  static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return -1; }
 static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
 # endif /* !NO_HZ */

-# ifdef CONFIG_CPU_IDLE_GOV_MENU
-extern void menu_hrtimer_cancel(void);
-# else
-static inline void menu_hrtimer_cancel(void) {}
-# endif /* CONFIG_CPU_IDLE_GOV_MENU */
-
 #endif
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 8853dab..b28e112 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -572,8 +572,6 @@  void tick_nohz_irq_exit(void)

 	local_irq_save(flags);

-	/* Cancel the timer because CPU already waken up from the C-states */
-	menu_hrtimer_cancel();
 	__tick_nohz_idle_enter(ts);

 	local_irq_restore(flags);
@@ -671,8 +669,6 @@  void tick_nohz_idle_exit(void)

 	ts->inidle = 0;

-	/* Cancel the timer because CPU already waken up from the C-states*/
-	menu_hrtimer_cancel();
 	if (ts->idle_active || ts->tick_stopped)
 		now = ktime_get();