Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966234Ab3HJQOr (ORCPT ); Sat, 10 Aug 2013 12:14:47 -0400 Received: from terminus.zytor.com ([198.137.202.10]:33060 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964808Ab3HJQOo (ORCPT ); Sat, 10 Aug 2013 12:14:44 -0400 Date: Sat, 10 Aug 2013 09:14:27 -0700 From: tip-bot for Jeremy Fitzhardinge Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, konrad.wilk@oracle.com, jeremy@goop.org, raghavendra.kt@linux.vnet.ibm.com, tglx@linutronix.de, hpa@linux.intel.com, attilio.rao@citrix.com Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, konrad.wilk@oracle.com, jeremy@goop.org, raghavendra.kt@linux.vnet.ibm.com, tglx@linutronix.de, hpa@linux.intel.com, attilio.rao@citrix.com In-Reply-To: <1376058122-8248-9-git-send-email-raghavendra.kt@linux.vnet.ibm.com> References: <1376058122-8248-9-git-send-email-raghavendra.kt@linux.vnet.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/spinlocks] x86, pvticketlock: When paravirtualizing ticket locks, increment by 2 Git-Commit-ID: 4a1ed4ca681e7df38ed1b609a11aab38cbc515b3 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (terminus.zytor.com [127.0.0.1]); Sat, 10 Aug 2013 09:14:34 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3960 Lines: 104 Commit-ID: 4a1ed4ca681e7df38ed1b609a11aab38cbc515b3 Gitweb: http://git.kernel.org/tip/4a1ed4ca681e7df38ed1b609a11aab38cbc515b3 Author: Jeremy Fitzhardinge AuthorDate: Fri, 9 Aug 2013 19:51:56 +0530 Committer: H. Peter Anvin CommitDate: Fri, 9 Aug 2013 07:53:50 -0700 x86, pvticketlock: When paravirtualizing ticket locks, increment by 2 Increment ticket head/tails by 2 rather than 1 to leave the LSB free to store a "is in slowpath state" bit. This halves the number of possible CPUs for a given ticket size, but this shouldn't matter in practice - kernels built for 32k+ CPU systems are probably specially built for the hardware rather than a generic distro kernel. Signed-off-by: Jeremy Fitzhardinge Link: http://lkml.kernel.org/r/1376058122-8248-9-git-send-email-raghavendra.kt@linux.vnet.ibm.com Reviewed-by: Konrad Rzeszutek Wilk Tested-by: Attilio Rao Signed-off-by: Raghavendra K T Acked-by: Ingo Molnar Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/spinlock.h | 10 +++++----- arch/x86/include/asm/spinlock_types.h | 10 +++++++++- 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index 7442410..04a5cd5 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -78,7 +78,7 @@ static __always_inline void __ticket_unlock_kick(struct arch_spinlock *lock, */ static __always_inline void arch_spin_lock(struct arch_spinlock *lock) { - register struct __raw_tickets inc = { .tail = 1 }; + register struct __raw_tickets inc = { .tail = TICKET_LOCK_INC }; inc = xadd(&lock->tickets, inc); @@ -104,7 +104,7 @@ static __always_inline int arch_spin_trylock(arch_spinlock_t *lock) if (old.tickets.head != old.tickets.tail) return 0; - new.head_tail = old.head_tail + (1 << TICKET_SHIFT); + new.head_tail = old.head_tail + (TICKET_LOCK_INC << TICKET_SHIFT); /* cmpxchg is a full barrier, so nothing can move before it */ return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail; @@ -112,9 +112,9 @@ static __always_inline int arch_spin_trylock(arch_spinlock_t *lock) static __always_inline void arch_spin_unlock(arch_spinlock_t *lock) { - __ticket_t next = lock->tickets.head + 1; + __ticket_t next = lock->tickets.head + TICKET_LOCK_INC; - __add(&lock->tickets.head, 1, UNLOCK_LOCK_PREFIX); + __add(&lock->tickets.head, TICKET_LOCK_INC, UNLOCK_LOCK_PREFIX); __ticket_unlock_kick(lock, next); } @@ -129,7 +129,7 @@ static inline int arch_spin_is_contended(arch_spinlock_t *lock) { struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets); - return (__ticket_t)(tmp.tail - tmp.head) > 1; + return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC; } #define arch_spin_is_contended arch_spin_is_contended diff --git a/arch/x86/include/asm/spinlock_types.h b/arch/x86/include/asm/spinlock_types.h index 83fd3c7..e96fcbd 100644 --- a/arch/x86/include/asm/spinlock_types.h +++ b/arch/x86/include/asm/spinlock_types.h @@ -3,7 +3,13 @@ #include -#if (CONFIG_NR_CPUS < 256) +#ifdef CONFIG_PARAVIRT_SPINLOCKS +#define __TICKET_LOCK_INC 2 +#else +#define __TICKET_LOCK_INC 1 +#endif + +#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_INC)) typedef u8 __ticket_t; typedef u16 __ticketpair_t; #else @@ -11,6 +17,8 @@ typedef u16 __ticket_t; typedef u32 __ticketpair_t; #endif +#define TICKET_LOCK_INC ((__ticket_t)__TICKET_LOCK_INC) + #define TICKET_SHIFT (sizeof(__ticket_t) * 8) typedef struct arch_spinlock { -- 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/