release 6.12.4 (preliminary)
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@@ -1,26 +1,35 @@
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From d31e903a364802c068ff23bdd448cc70eda71a7c Mon Sep 17 00:00:00 2001
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From 3d722d5259babc1650ab6cb1a8bbf27863af75f2 Mon Sep 17 00:00:00 2001
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From: Christian Loehle <christian.loehle@arm.com>
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Date: Thu, 5 Sep 2024 10:26:38 +0100
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Subject: cpuidle: menu: Remove iowait influence
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Remove CPU iowaiters influence on idle state selection.
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Remove the menu notion of performance multiplier which increased with
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the number of tasks that went to iowait sleep on this CPU and haven't
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woken up yet.
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Relying on iowait for cpuidle is problematic for a few reasons:
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1. There is no guarantee that an iowaiting task will wake up on the
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same CPU.
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2. The task being in iowait says nothing about the idle duration, we
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could be selecting shallower states for a long time.
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3. The task being in iowait doesn't always imply a performance hit
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with increased latency.
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4. If there is such a performance hit, the number of iowaiting tasks
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doesn't directly correlate.
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5. The definition of iowait altogether is vague at best, it is
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sprinkled across kernel code.
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1. There is no guarantee that an iowaiting task will wake up on the
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same CPU.
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2. The task being in iowait says nothing about the idle duration, we
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could be selecting shallower states for a long time.
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3. The task being in iowait doesn't always imply a performance hit
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with increased latency.
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4. If there is such a performance hit, the number of iowaiting tasks
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doesn't directly correlate.
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5. The definition of iowait altogether is vague at best, it is
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sprinkled across kernel code.
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Signed-off-by: Christian Loehle <christian.loehle@arm.com>
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Link: https://patch.msgid.link/20240905092645.2885200-2-christian.loehle@arm.com
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[ rjw: Minor edits in the changelog ]
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Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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---
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drivers/cpuidle/governors/menu.c | 76 ++++----------------------------
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1 file changed, 9 insertions(+), 67 deletions(-)
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