[tip:core/locking] x86/locking/kconfig: Update paravirt spinlock Kconfig description

From: tip-bot for Raghavendra K T
Date: Sat Oct 26 2013 - 09:52:55 EST

Commit-ID: 4c4e4f61368164f326fe59e2156c70d7faa72c17
Gitweb: http://git.kernel.org/tip/4c4e4f61368164f326fe59e2156c70d7faa72c17
Author: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 21 Oct 2013 21:35:08 +0530
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sat, 26 Oct 2013 12:23:22 +0200

x86/locking/kconfig: Update paravirt spinlock Kconfig description

Since the paravirt spinlock optimizations went into the v3.12 kernel
we have a very good performance benefit for paravirtualized KVM / Xen
kernels. Also we no longer suffer from 5% side effect on native
kernel that is mentioned in the Kconfig entry.

So update the Kconfig entry accordingly.

pvspinlock benefit on KVM link:


Attilio's tests on native kernel impact:


Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Cc: <konrad.wilk@xxxxxxxxxx>
Cc: <linux@xxxxxxxxxxxxxx>
Cc: <gleb@xxxxxxxxxx>
Cc: <pbonzini@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1382371508-3843-1-git-send-email-raghavendra.kt@xxxxxxxxxxxxxxxxxx
[ Updated the changelog. ]
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
arch/x86/Kconfig | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ee2fb9d..a92572d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -638,10 +638,10 @@ config PARAVIRT_SPINLOCKS
spinlock implementation with something virtualization-friendly
(for example, block the virtual CPU rather than spinning).

- Unfortunately the downside is an up to 5% performance hit on
- native kernels, with various workloads.
+ It has a minimal impact on native kernels and gives a nice performance
+ benefit on paravirtualized KVM / Xen kernels.

- If you are unsure how to answer this question, answer N.
+ If you are unsure how to answer this question, answer Y.

source "arch/x86/xen/Kconfig"

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