linux-kernel - [PATCH RFC V9 7/19] x86/pvticketlock: Use callee-save for lock

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Date:	Sun, 02 Jun 2013 00:53:42 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	<gleb@...hat.com>, <mingo@...hat.com>, <jeremy@...p.org>,
	<x86@...nel.org>, <konrad.wilk@...cle.com>, <hpa@...or.com>,
	<pbonzini@...hat.com>
Cc:	linux-doc@...r.kernel.org, <habanero@...ux.vnet.ibm.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	<xen-devel@...ts.xensource.com>, <peterz@...radead.org>,
	<mtosatti@...hat.com>, <stefano.stabellini@...citrix.com>,
	<andi@...stfloor.org>, <attilio.rao@...rix.com>,
	<ouyang@...pitt.edu>, <gregkh@...e.de>, <agraf@...e.de>,
	<chegu_vinod@...com>, <torvalds@...ux-foundation.org>,
	<avi.kivity@...il.com>, <tglx@...utronix.de>,
	<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<stephan.diestelhorst@....com>, <riel@...hat.com>,
	<drjones@...hat.com>, <virtualization@...ts.linux-foundation.org>,
	<srivatsa.vaddagiri@...il.com>
Subject: [PATCH RFC V9 7/19]  x86/pvticketlock: Use callee-save for lock_spinning

x86/pvticketlock: Use callee-save for lock_spinning

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

Although the lock_spinning calls in the spinlock code are on the
uncommon path, their presence can cause the compiler to generate many
more register save/restores in the function pre/postamble, which is in
the fast path.  To avoid this, convert it to using the pvops callee-save
calling convention, which defers all the save/restores until the actual
function is called, keeping the fastpath clean.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Tested-by: Attilio Rao <attilio.rao@...rix.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
---
 arch/x86/include/asm/paravirt.h       |    2 +-
 arch/x86/include/asm/paravirt_types.h |    2 +-
 arch/x86/kernel/paravirt-spinlocks.c  |    2 +-
 arch/x86/xen/spinlock.c               |    3 ++-
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 040e72d..7131e12c 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -715,7 +715,7 @@ static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx,
 static __always_inline void __ticket_lock_spinning(struct arch_spinlock *lock,
 							__ticket_t ticket)
 {
-	PVOP_VCALL2(pv_lock_ops.lock_spinning, lock, ticket);
+	PVOP_VCALLEE2(pv_lock_ops.lock_spinning, lock, ticket);
 }
 
 static __always_inline void ____ticket_unlock_kick(struct arch_spinlock *lock,
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index d5deb6d..350d017 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -330,7 +330,7 @@ struct arch_spinlock;
 #include <asm/spinlock_types.h>
 
 struct pv_lock_ops {
-	void (*lock_spinning)(struct arch_spinlock *lock, __ticket_t ticket);
+	struct paravirt_callee_save lock_spinning;
 	void (*unlock_kick)(struct arch_spinlock *lock, __ticket_t ticket);
 };
 
diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
index c2e010e..4251c1d 100644
--- a/arch/x86/kernel/paravirt-spinlocks.c
+++ b/arch/x86/kernel/paravirt-spinlocks.c
@@ -9,7 +9,7 @@
 
 struct pv_lock_ops pv_lock_ops = {
 #ifdef CONFIG_SMP
-	.lock_spinning = paravirt_nop,
+	.lock_spinning = __PV_IS_CALLEE_SAVE(paravirt_nop),
 	.unlock_kick = paravirt_nop,
 #endif
 };
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 3de6805..5502fda 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -171,6 +171,7 @@ out:
 	local_irq_restore(flags);
 	spin_time_accum_blocked(start);
 }
+PV_CALLEE_SAVE_REGS_THUNK(xen_lock_spinning);
 
 static void xen_unlock_kick(struct arch_spinlock *lock, __ticket_t next)
 {
@@ -254,7 +255,7 @@ void __init xen_init_spinlocks(void)
 		return;
 	}
 
-	pv_lock_ops.lock_spinning = xen_lock_spinning;
+	pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning);
 	pv_lock_ops.unlock_kick = xen_unlock_kick;
 }
 

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