This is a note to let you know that I've just added the patch titled
x86 idle: Repair large-server 50-watt idle-power regression
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-idle-repair-large-server-50-watt-idle-power-regression.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 40e2d7f9b5dae048789c64672bf3027fbb663ffa Mon Sep 17 00:00:00 2001
From: Len Brown <[email protected]>
Date: Wed, 18 Dec 2013 16:44:57 -0500
Subject: x86 idle: Repair large-server 50-watt idle-power regression
From: Len Brown <[email protected]>
commit 40e2d7f9b5dae048789c64672bf3027fbb663ffa upstream.
Linux 3.10 changed the timing of how thread_info->flags is touched:
x86: Use generic idle loop
(7d1a941731fabf27e5fb6edbebb79fe856edb4e5)
This caused Intel NHM-EX and WSM-EX servers to experience a large number
of immediate MONITOR/MWAIT break wakeups, which caused cpuidle to demote
from deep C-states to shallow C-states, which caused these platforms
to experience a significant increase in idle power.
Note that this issue was already present before the commit above,
however, it wasn't seen often enough to be noticed in power measurements.
Here we extend an errata workaround from the Core2 EX "Dunnington"
to extend to NHM-EX and WSM-EX, to prevent these immediate
returns from MWAIT, reducing idle power on these platforms.
While only acpi_idle ran on Dunnington, intel_idle
may also run on these two newer systems.
As of today, there are no other models that are known
to need this tweak.
Link:
http://lkml.kernel.org/r/CAJvTdK=%[email protected]
Signed-off-by: Len Brown <[email protected]>
Link:
http://lkml.kernel.org/r/baff264285f6e585df757d58b17788feabc68918.1387403066.git.len.br...@intel.com
Signed-off-by: H. Peter Anvin <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/x86/kernel/cpu/intel.c | 3 ++-
drivers/idle/intel_idle.c | 3 +++
2 files changed, 5 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -387,7 +387,8 @@ static void init_intel(struct cpuinfo_x8
set_cpu_cap(c, X86_FEATURE_PEBS);
}
- if (c->x86 == 6 && c->x86_model == 29 && cpu_has_clflush)
+ if (c->x86 == 6 && cpu_has_clflush &&
+ (c->x86_model == 29 || c->x86_model == 46 || c->x86_model == 47))
set_cpu_cap(c, X86_FEATURE_CLFLUSH_MONITOR);
#ifdef CONFIG_X86_64
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -361,6 +361,9 @@ static int intel_idle(struct cpuidle_dev
if (!current_set_polling_and_test()) {
+ if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
+ clflush((void *)¤t_thread_info()->flags);
+
__monitor((void *)¤t_thread_info()->flags, 0, 0);
smp_mb();
if (!need_resched())
Patches currently in stable-queue which might be from [email protected] are
queue-3.12/x86-idle-repair-large-server-50-watt-idle-power-regression.patch
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