[PATCH] x86 kconfig: Add recommendation to enable paravirt spinlock

[PATCH] x86 kconfig: Add recommendation to enable paravirt spinlock

[Raghavendra K T]

Since paravirt spinlock optimization are in 3.12 kernel, we have
very good performance benefit for paravirtualized KVM / Xen kernel.
Also we no longer suffer from 5% side effect on native kernel.

Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
---
 Would like to thank Sander for spotting and suggesting this.
 pvspinlock benefit on KVM link: https://lkml.org/lkml/2013/8/6/178 
 
 Attilio's tests on native kernel impact:
 http://blog.xen.org/index.php/2012/05/11/benchmarking-the-new-pv-ticketlock-implementation/

 arch/x86/Kconfig | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f67e839..4ba9d32 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 minimal impact on native kernels and gives nice performance
+	  benefit for 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"
 
-- 
1.7.11.7

Re: [PATCH] x86 kconfig: Add recommendation to enable paravirt spinlock

[Konrad Rzeszutek Wilk]

On Mon, Oct 21, 2013 at 09:35:08PM +0530, Raghavendra K T wrote:
> Since paravirt spinlock optimization are in 3.12 kernel, we have
> very good performance benefit for paravirtualized KVM / Xen kernel.
> Also we no longer suffer from 5% side effect on native kernel.

Yeey!
> 
> Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
> ---
>  Would like to thank Sander for spotting and suggesting this.
>  pvspinlock benefit on KVM link: https://lkml.org/lkml/2013/8/6/178 
>  
>  Attilio's tests on native kernel impact:
>  http://blog.xen.org/index.php/2012/05/11/benchmarking-the-new-pv-ticketlock-implementation/
> 
>  arch/x86/Kconfig | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index f67e839..4ba9d32 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 minimal impact on native kernels and gives nice performance
> +	  benefit for 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"
>  
> -- 
> 1.7.11.7
> 

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

[tip-bot for Raghavendra K T]

Commit-ID:  4c4e4f61368164f326fe59e2156c70d7faa72c17
Gitweb:     http://git.kernel.org/tip/4c4e4f61368164f326fe59e2156c70d7faa72c17
Author:     Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
AuthorDate: Mon, 21 Oct 2013 21:35:08 +0530
Committer:  Ingo Molnar <mingo@kernel.org>
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:

  https://lkml.org/lkml/2013/8/6/178

Attilio's tests on native kernel impact:

  http://blog.xen.org/index.php/2012/05/11/benchmarking-the-new-pv-ticketlock-implementation/

Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: <konrad.wilk@oracle.com>
Cc: <linux@eikelenboom.it>
Cc: <gleb@redhat.com>
Cc: <pbonzini@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1382371508-3843-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com
[ Updated the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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"