path: root/drivers/idle
diff options
authorLen Brown <>2013-12-18 16:44:57 -0500
committerH. Peter Anvin <>2013-12-19 11:47:39 -0800
commit40e2d7f9b5dae048789c64672bf3027fbb663ffa (patch)
tree927f4eed6788b6e07a80edf905f1e63780b1ea1f /drivers/idle
parent319e2e3f63c348a9b66db4667efa73178e18b17d (diff)
x86 idle: Repair large-server 50-watt idle-power regression
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: Signed-off-by: Len Brown <> Link: Cc: <> # 3.12.x, 3.11.x, 3.10.x Signed-off-by: H. Peter Anvin <>
Diffstat (limited to 'drivers/idle')
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 92d1206482a6..f80b700f821c 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -377,6 +377,9 @@ static int intel_idle(struct cpuidle_device *dev,
if (!current_set_polling_and_test()) {
+ if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
+ clflush((void *)&current_thread_info()->flags);
__monitor((void *)&current_thread_info()->flags, 0, 0);
if (!need_resched())