Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751905AbWISLTk (ORCPT ); Tue, 19 Sep 2006 07:19:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751907AbWISLTk (ORCPT ); Tue, 19 Sep 2006 07:19:40 -0400 Received: from mtagate2.de.ibm.com ([195.212.29.151]:61834 "EHLO mtagate2.de.ibm.com") by vger.kernel.org with ESMTP id S1751900AbWISLTi (ORCPT ); Tue, 19 Sep 2006 07:19:38 -0400 Date: Tue, 19 Sep 2006 13:19:34 +0200 From: Martin Schwidefsky To: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@osdl.org Cc: mingo@elte.hu, paulus@samba.org Subject: [patch 1/3] Directed yield: cpu_relax variants for spinlocks and rw-locks. Message-ID: <20060919111934.GC21713@skybase> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 11372 Lines: 255 From: Martin Schwidefsky [patch 1/3] Directed yield: cpu_relax variants for spinlocks and rw-locks. On systems running with virtual cpus there is optimization potential in regard to spinlocks and rw-locks. If the virtual cpu that has taken a lock is known to a cpu that wants to acquire the same lock it is beneficial to yield the timeslice of the virtual cpu in favour of the cpu that has the lock (directed yield). With CONFIG_PREEMPT="n" this can be implemented by the architecture without common code changes. Powerpc already does this. With CONFIG_PREEMPT="y" the lock loops are coded with _raw_spin_trylock, _raw_read_trylock and _raw_write_trylock in kernel/spinlock.c. If the lock could not be taken cpu_relax is called. A directed yield is not possible because cpu_relax doesn't know anything about the lock. To be able to yield the lock in favour of the current lock holder variants of cpu_relax for spinlocks and rw-locks are needed. The new _raw_spin_relax, _raw_read_relax and _raw_write_relax primitives differ from cpu_relax insofar that they have an argument: a pointer to the lock structure. Signed-off-by: Martin Schwidefsky --- include/asm-alpha/spinlock.h | 4 ++++ include/asm-arm/spinlock.h | 4 ++++ include/asm-cris/arch-v32/spinlock.h | 4 ++++ include/asm-i386/spinlock.h | 4 ++++ include/asm-ia64/spinlock.h | 4 ++++ include/asm-m32r/spinlock.h | 4 ++++ include/asm-mips/spinlock.h | 4 ++++ include/asm-parisc/spinlock.h | 4 ++++ include/asm-powerpc/spinlock.h | 4 ++++ include/asm-ppc/spinlock.h | 4 ++++ include/asm-s390/spinlock.h | 4 ++++ include/asm-sh/spinlock.h | 4 ++++ include/asm-sparc/spinlock.h | 4 ++++ include/asm-sparc64/spinlock.h | 4 ++++ include/asm-x86_64/spinlock.h | 4 ++++ kernel/spinlock.c | 4 ++-- 16 files changed, 62 insertions(+), 2 deletions(-) diff -urpN linux-2.6/include/asm-alpha/spinlock.h linux-2.6-patched/include/asm-alpha/spinlock.h --- linux-2.6/include/asm-alpha/spinlock.h 2006-09-19 12:58:36.000000000 +0200 +++ linux-2.6-patched/include/asm-alpha/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -166,4 +166,8 @@ static inline void __raw_write_unlock(ra lock->lock = 0; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* _ALPHA_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-arm/spinlock.h linux-2.6-patched/include/asm-arm/spinlock.h --- linux-2.6/include/asm-arm/spinlock.h 2006-09-19 12:58:36.000000000 +0200 +++ linux-2.6-patched/include/asm-arm/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -218,4 +218,8 @@ static inline int __raw_read_trylock(raw /* read_can_lock - would read_trylock() succeed? */ #define __raw_read_can_lock(x) ((x)->lock < 0x80000000) +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-cris/arch-v32/spinlock.h linux-2.6-patched/include/asm-cris/arch-v32/spinlock.h --- linux-2.6/include/asm-cris/arch-v32/spinlock.h 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6-patched/include/asm-cris/arch-v32/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -160,4 +160,8 @@ static __inline__ int is_write_locked(rw return rw->counter < 0; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_ARCH_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-i386/spinlock.h linux-2.6-patched/include/asm-i386/spinlock.h --- linux-2.6/include/asm-i386/spinlock.h 2006-09-19 12:58:37.000000000 +0200 +++ linux-2.6-patched/include/asm-i386/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -199,4 +199,8 @@ static inline void __raw_write_unlock(ra : "+m" (rw->lock) : : "memory"); } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-ia64/spinlock.h linux-2.6-patched/include/asm-ia64/spinlock.h --- linux-2.6/include/asm-ia64/spinlock.h 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6-patched/include/asm-ia64/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -213,4 +213,8 @@ static inline int __raw_read_trylock(raw return (u32)ia64_cmpxchg4_acq((__u32 *)(x), new.word, old.word) == old.word; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* _ASM_IA64_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-m32r/spinlock.h linux-2.6-patched/include/asm-m32r/spinlock.h --- linux-2.6/include/asm-m32r/spinlock.h 2006-09-19 12:58:37.000000000 +0200 +++ linux-2.6-patched/include/asm-m32r/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -309,4 +309,8 @@ static inline int __raw_write_trylock(ra return 0; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* _ASM_M32R_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-mips/spinlock.h linux-2.6-patched/include/asm-mips/spinlock.h --- linux-2.6/include/asm-mips/spinlock.h 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6-patched/include/asm-mips/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -283,4 +283,8 @@ static inline int __raw_write_trylock(ra return ret; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* _ASM_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-parisc/spinlock.h linux-2.6-patched/include/asm-parisc/spinlock.h --- linux-2.6/include/asm-parisc/spinlock.h 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6-patched/include/asm-parisc/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -152,4 +152,8 @@ static __inline__ int __raw_write_can_lo return !rw->counter; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-powerpc/spinlock.h linux-2.6-patched/include/asm-powerpc/spinlock.h --- linux-2.6/include/asm-powerpc/spinlock.h 2006-09-19 12:58:37.000000000 +0200 +++ linux-2.6-patched/include/asm-powerpc/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -285,5 +285,9 @@ static __inline__ void __raw_write_unloc rw->lock = 0; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __KERNEL__ */ #endif /* __ASM_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-ppc/spinlock.h linux-2.6-patched/include/asm-ppc/spinlock.h --- linux-2.6/include/asm-ppc/spinlock.h 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6-patched/include/asm-ppc/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -161,4 +161,8 @@ static __inline__ void __raw_write_unloc rw->lock = 0; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-s390/spinlock.h linux-2.6-patched/include/asm-s390/spinlock.h --- linux-2.6/include/asm-s390/spinlock.h 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6-patched/include/asm-s390/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -135,4 +135,8 @@ static inline int __raw_write_trylock(ra return _raw_write_trylock_retry(rw); } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-sh/spinlock.h linux-2.6-patched/include/asm-sh/spinlock.h --- linux-2.6/include/asm-sh/spinlock.h 2006-06-18 03:49:35.000000000 +0200 +++ linux-2.6-patched/include/asm-sh/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -100,4 +100,8 @@ static inline int __raw_write_trylock(ra return 0; } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_SH_SPINLOCK_H */ diff -urpN linux-2.6/include/asm-sparc/spinlock.h linux-2.6-patched/include/asm-sparc/spinlock.h --- linux-2.6/include/asm-sparc/spinlock.h 2006-09-19 12:58:37.000000000 +0200 +++ linux-2.6-patched/include/asm-sparc/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -154,6 +154,10 @@ static inline int __raw_write_trylock(ra #define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock) #define __raw_read_trylock(lock) generic__raw_read_trylock(lock) +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #define __raw_read_can_lock(rw) (!((rw)->lock & 0xff)) #define __raw_write_can_lock(rw) (!(rw)->lock) diff -urpN linux-2.6/include/asm-sparc64/spinlock.h linux-2.6-patched/include/asm-sparc64/spinlock.h --- linux-2.6/include/asm-sparc64/spinlock.h 2006-09-19 12:58:37.000000000 +0200 +++ linux-2.6-patched/include/asm-sparc64/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -241,6 +241,10 @@ static int inline __write_trylock(raw_rw #define __raw_read_can_lock(rw) (!((rw)->lock & 0x80000000UL)) #define __raw_write_can_lock(rw) (!(rw)->lock) +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* !(__ASSEMBLY__) */ #endif /* !(__SPARC64_SPINLOCK_H) */ diff -urpN linux-2.6/include/asm-x86_64/spinlock.h linux-2.6-patched/include/asm-x86_64/spinlock.h --- linux-2.6/include/asm-x86_64/spinlock.h 2006-09-19 12:58:37.000000000 +0200 +++ linux-2.6-patched/include/asm-x86_64/spinlock.h 2006-09-19 12:59:34.000000000 +0200 @@ -131,4 +131,8 @@ static inline void __raw_write_unlock(ra : "=m" (rw->lock) : : "memory"); } +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_SPINLOCK_H */ diff -urpN linux-2.6/kernel/spinlock.c linux-2.6-patched/kernel/spinlock.c --- linux-2.6/kernel/spinlock.c 2006-09-19 12:58:38.000000000 +0200 +++ linux-2.6-patched/kernel/spinlock.c 2006-09-19 12:59:34.000000000 +0200 @@ -221,7 +221,7 @@ void __lockfunc _##op##_lock(locktype##_ if (!(lock)->break_lock) \ (lock)->break_lock = 1; \ while (!op##_can_lock(lock) && (lock)->break_lock) \ - cpu_relax(); \ + _raw_##op##_relax(&lock->raw_lock); \ } \ (lock)->break_lock = 0; \ } \ @@ -243,7 +243,7 @@ unsigned long __lockfunc _##op##_lock_ir if (!(lock)->break_lock) \ (lock)->break_lock = 1; \ while (!op##_can_lock(lock) && (lock)->break_lock) \ - cpu_relax(); \ + _raw_##op##_relax(&lock->raw_lock); \ } \ (lock)->break_lock = 0; \ return flags; \ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/