From patchwork Mon Feb 25 15:53:22 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lai Jiangshan X-Patchwork-Id: 2181411 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by patchwork1.kernel.org (Postfix) with ESMTP id 0F7FF3FD4E for ; Mon, 25 Feb 2013 15:56:42 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1UA0Mq-0000wC-8L; Mon, 25 Feb 2013 15:53:28 +0000 Received: from ie-in-x022f.1e100.net ([2607:f8b0:4001:c03::22f] helo=mail-ie0-x22f.google.com) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1UA0Mm-0000vc-FE for linux-arm-kernel@lists.infradead.org; Mon, 25 Feb 2013 15:53:25 +0000 Received: by mail-ie0-f175.google.com with SMTP id c12so3265086ieb.34 for ; Mon, 25 Feb 2013 07:53:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:x-received:in-reply-to:references:date:message-id :subject:from:to:cc:content-type; bh=sxUfgTUGm4fgShqZdHOq525Hgx01Zf81r+BxdrhI72g=; b=m6V5yQeqkJVcTI4aDJSUzPOJiViACsMjK42Dl71vWqiv67WV8ar+YYiktp7eLWb7Ik FDW1nSJlSmltmwcDA+Mi/Hg+RhBQ0qUoFUBPoBhUYkzYqp+IP10iI1Z5ZboBQG+AhRot /X0/t1mujme2rS/tLaZhUqJxMhFpz6KtzNgGVV1+W0T8VXvvlavT3rctqnh6eUDAlVnr e12ZhRA/9w3BaKpsFq+x50rG7TzA9ecsVriI6gt10cEs+433VSBdldvyb1fjGIfljj1B fe/bjV1AjOrmnjF9/OW/MaotRMTwaFaZ2GxL4h+tWiUVlT7WQYKiwpSeQOA/qO1m3Iic Gp5A== MIME-Version: 1.0 X-Received: by 10.50.173.9 with SMTP id bg9mr3846240igc.82.1361807602632; Mon, 25 Feb 2013 07:53:22 -0800 (PST) Received: by 10.64.101.228 with HTTP; Mon, 25 Feb 2013 07:53:22 -0800 (PST) In-Reply-To: <51226F91.7000108@linux.vnet.ibm.com> References: <20130218123714.26245.61816.stgit@srivatsabhat.in.ibm.com> <20130218123856.26245.46705.stgit@srivatsabhat.in.ibm.com> <5122551E.1080703@linux.vnet.ibm.com> <51226B46.9080707@linux.vnet.ibm.com> <51226F91.7000108@linux.vnet.ibm.com> Date: Mon, 25 Feb 2013 23:53:22 +0800 Message-ID: Subject: Re: [PATCH v6 04/46] percpu_rwlock: Implement the core design of Per-CPU Reader-Writer Locks From: Lai Jiangshan To: "Srivatsa S. Bhat" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130225_105324_542489_63BEA2F2 X-CRM114-Status: GOOD ( 13.68 ) X-Spam-Score: 1.2 (+) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (1.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- 3.0 KHOP_BIG_TO_CC Sent to 10+ recipients instaed of Bcc or a list 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (eag0628[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.2 FREEMAIL_ENVFROM_END_DIGIT Envelope-from freemail username ends in digit (eag0628[at]gmail.com) -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature Cc: linux-doc@vger.kernel.org, peterz@infradead.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org, Michel Lespinasse , mingo@kernel.org, linux-arch@vger.kernel.org, linux@arm.linux.org.uk, xiaoguangrong@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, paulmck@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, rusty@rustcorp.com.au, rostedt@goodmis.org, rjw@sisk.pl, namhyung@kernel.org, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, oleg@redhat.com, vincent.guittot@linaro.org, sbw@mit.edu, tj@kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Hi, Srivatsa, The target of the whole patchset is nice for me. A question: How did you find out the such usages of "preempt_disable()" and convert them? did all are converted? And I think the lock is too complex and reinvent the wheel, why don't you reuse the lglock? I wrote an untested draft here. Thanks, Lai PS: Some HA tools(I'm writing one) which takes checkpoints of virtual-machines frequently, I guess this patchset can speedup the tools. From 01db542693a1b7fc6f9ece45d57cb529d9be5b66 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Mon, 25 Feb 2013 23:14:27 +0800 Subject: [PATCH] lglock: add read-preference local-global rwlock locality via lglock(trylock) read-preference read-write-lock via fallback rwlock_t Signed-off-by: Lai Jiangshan --- include/linux/lglock.h | 31 +++++++++++++++++++++++++++++++ kernel/lglock.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 76 insertions(+), 0 deletions(-) diff --git a/include/linux/lglock.h b/include/linux/lglock.h index 0d24e93..30fe887 100644 --- a/include/linux/lglock.h +++ b/include/linux/lglock.h @@ -67,4 +67,35 @@ void lg_local_unlock_cpu(struct lglock *lg, int cpu); void lg_global_lock(struct lglock *lg); void lg_global_unlock(struct lglock *lg); +struct lgrwlock { + unsigned long __percpu *fallback_reader_refcnt; + struct lglock lglock; + rwlock_t fallback_rwlock; +}; + +#define DEFINE_LGRWLOCK(name) \ + static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \ + = __ARCH_SPIN_LOCK_UNLOCKED; \ + static DEFINE_PER_CPU(unsigned long, name ## _refcnt); \ + struct lgrwlock name = { \ + .fallback_reader_refcnt = &name ## _refcnt, \ + .lglock = { .lock = &name ## _lock } } + +#define DEFINE_STATIC_LGRWLOCK(name) \ + static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \ + = __ARCH_SPIN_LOCK_UNLOCKED; \ + static DEFINE_PER_CPU(unsigned long, name ## _refcnt); \ + static struct lgrwlock name = { \ + .fallback_reader_refcnt = &name ## _refcnt, \ + .lglock = { .lock = &name ## _lock } } + +static inline void lg_rwlock_init(struct lgrwlock *lgrw, char *name) +{ + lg_lock_init(&lgrw->lglock, name); +} + +void lg_rwlock_local_read_lock(struct lgrwlock *lgrw); +void lg_rwlock_local_read_unlock(struct lgrwlock *lgrw); +void lg_rwlock_global_write_lock(struct lgrwlock *lgrw); +void lg_rwlock_global_write_unlock(struct lgrwlock *lgrw); #endif diff --git a/kernel/lglock.c b/kernel/lglock.c index 6535a66..463543a 100644 --- a/kernel/lglock.c +++ b/kernel/lglock.c @@ -87,3 +87,48 @@ void lg_global_unlock(struct lglock *lg) preempt_enable(); } EXPORT_SYMBOL(lg_global_unlock); + +void lg_rwlock_local_read_lock(struct lgrwlock *lgrw) +{ + struct lglock *lg = &lgrw->lglock; + + preempt_disable(); + if (likely(!__this_cpu_read(*lgrw->fallback_reader_refcnt))) { + if (likely(arch_spin_trylock(this_cpu_ptr(lg->lock)))) { + rwlock_acquire_read(&lg->lock_dep_map, 0, 0, _RET_IP_); + return; + } + read_lock(&lgrw->fallback_rwlock); + } + + __this_cpu_inc(*lgrw->fallback_reader_refcnt); +} +EXPORT_SYMBOL(lg_rwlock_local_read_lock); + +void lg_rwlock_local_read_unlock(struct lgrwlock *lgrw) +{ + if (likely(!__this_cpu_read(*lgrw->fallback_reader_refcnt))) { + lg_local_unlock(&lgrw->lglock); + return; + } + + if (!__this_cpu_dec_return(*lgrw->fallback_reader_refcnt)) + read_unlock(&lgrw->fallback_rwlock); + + preempt_enable(); +} +EXPORT_SYMBOL(lg_rwlock_local_read_unlock); + +void lg_rwlock_global_write_lock(struct lgrwlock *lgrw) +{ + lg_global_lock(&lgrw->lglock); + write_lock(&lgrw->fallback_rwlock); +} +EXPORT_SYMBOL(lg_rwlock_global_write_lock); + +void lg_rwlock_global_write_unlock(struct lgrwlock *lgrw) +{ + write_unlock(&lgrw->fallback_rwlock); + lg_global_unlock(&lgrw->lglock); +} +EXPORT_SYMBOL(lg_rwlock_global_write_unlock);