From patchwork Mon Jul 22 06:18:22 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Raghavendra K T X-Patchwork-Id: 2831054 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id ADF32C0319 for ; Mon, 22 Jul 2013 06:11:49 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id AF40820150 for ; Mon, 22 Jul 2013 06:11:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B896B20143 for ; Mon, 22 Jul 2013 06:11:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756500Ab3GVGLH (ORCPT ); Mon, 22 Jul 2013 02:11:07 -0400 Received: from e23smtp03.au.ibm.com ([202.81.31.145]:42155 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756492Ab3GVGLE (ORCPT ); Mon, 22 Jul 2013 02:11:04 -0400 Received: from /spool/local by e23smtp03.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 22 Jul 2013 16:00:48 +1000 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id 9575E2CE804C; Mon, 22 Jul 2013 16:10:59 +1000 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r6M6AnMZ7668208; Mon, 22 Jul 2013 16:10:49 +1000 Received: from d23av02.au.ibm.com (loopback [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r6M6Asc0003444; Mon, 22 Jul 2013 16:10:59 +1000 Received: from [9.124.158.46] ([9.124.158.46]) by d23av02.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id r6M6Amcb003228; Mon, 22 Jul 2013 16:10:49 +1000 From: Raghavendra K T To: , , , , , , Cc: linux-doc@vger.kernel.org, , Raghavendra K T , , , , , , , , , , , , , , , , , , , Date: Mon, 22 Jul 2013 11:48:22 +0530 Message-Id: <20130722061822.24737.54652.sendpatchset@codeblue> In-Reply-To: <20130722061631.24737.75508.sendpatchset@codeblue> References: <20130722061631.24737.75508.sendpatchset@codeblue> Subject: [PATCH RFC V11 8/18] x86/pvticketlock: When paravirtualizing ticket locks, increment by 2 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13072206-6102-0000-0000-000003E546BF Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-8.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP x86/pvticketlock: When paravirtualizing ticket locks, increment by 2 From: Jeremy Fitzhardinge 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 Reviewed-by: Konrad Rzeszutek Wilk Tested-by: Attilio Rao Signed-off-by: Raghavendra K T --- arch/x86/include/asm/spinlock.h | 10 +++++----- arch/x86/include/asm/spinlock_types.h | 10 +++++++++- 2 files changed, 14 insertions(+), 6 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html 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 {