From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84DA5C433E0 for ; Tue, 23 Jun 2020 00:31:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D0B02053B for ; Tue, 23 Jun 2020 00:31:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592872273; bh=bZg5gBncijoyMWdgbYgciJ0sPWgsDJ5wkZfgfN5L2DA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YLzf8B9xNykC5yE4+SGvila/+GG+0ack3TglDi7cFIsxfmt6TewadXGNqFSQITLnJ ZMmPBk5r/YlVMQR8fJvHsq6ZeT8Yxf/13Ln1zyDK1Gs3UNR6TvxppzvErnag9HbQ/C BWtM5CVaNHPhQqKEfWxJobo/F/deFww6HpkDKKIg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731548AbgFWAbL (ORCPT ); Mon, 22 Jun 2020 20:31:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:55258 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731689AbgFWAaU (ORCPT ); Mon, 22 Jun 2020 20:30:20 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 438E2208B8; Tue, 23 Jun 2020 00:30:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592872219; bh=bZg5gBncijoyMWdgbYgciJ0sPWgsDJ5wkZfgfN5L2DA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V75LN1StpBbfVYMH0Ywd1gn7pSoFauo7c5xiXMtF11DNxSmcYZRXPKZPirKnVc2cc EjpHwUZyUagLntfDInShjf3UwikiOE0DQJ4ofJMkkMCRbql+49ZUSXuT01S6ySK3Zb bukeA9mljNQc8Wo5BY8+wjSPL3hgMCcnna0PLtwg= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 20/30] refperf: Add read-side delay module parameter Date: Mon, 22 Jun 2020 17:30:03 -0700 Message-Id: <20200623003013.26252-20-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200623002941.GA26089@paulmck-ThinkPad-P72> References: <20200623002941.GA26089@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" This commit adds a refperf.readdelay module parameter that controls the duration of each critical section. This parameter allows gathering data showing how the performance differences between the various primitives vary with critical-section length. Cc: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- kernel/rcu/refperf.c | 108 ++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 89 insertions(+), 19 deletions(-) diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c index 7839237..57a750b 100644 --- a/kernel/rcu/refperf.c +++ b/kernel/rcu/refperf.c @@ -66,8 +66,8 @@ torture_param(long, loops, 10000000, "Number of loops per experiment."); torture_param(int, nreaders, -1, "Number of readers, -1 for 75% of CPUs."); // Number of runs. torture_param(int, nruns, 30, "Number of experiments to run."); -// Reader delay in nanoseconds, 0 for no delay. -torture_param(int, readdelay, 0, "Read-side delay in nanoseconds."); +// Reader delay in microseconds, 0 for no delay. +torture_param(int, readdelay, 0, "Read-side delay in microseconds."); #ifdef MODULE # define REFPERF_SHUTDOWN 0 @@ -111,6 +111,7 @@ struct ref_perf_ops { void (*init)(void); void (*cleanup)(void); void (*readsection)(const int nloops); + void (*delaysection)(const int nloops, const int ndelay); const char *name; }; @@ -126,6 +127,17 @@ static void ref_rcu_read_section(const int nloops) } } +static void ref_rcu_delay_section(const int nloops, const int ndelay) +{ + int i; + + for (i = nloops; i >= 0; i--) { + rcu_read_lock(); + udelay(ndelay); + rcu_read_unlock(); + } +} + static void rcu_sync_perf_init(void) { } @@ -133,6 +145,7 @@ static void rcu_sync_perf_init(void) static struct ref_perf_ops rcu_ops = { .init = rcu_sync_perf_init, .readsection = ref_rcu_read_section, + .delaysection = ref_rcu_delay_section, .name = "rcu" }; @@ -141,7 +154,7 @@ static struct ref_perf_ops rcu_ops = { DEFINE_STATIC_SRCU(srcu_refctl_perf); static struct srcu_struct *srcu_ctlp = &srcu_refctl_perf; -static void srcu_ref_perf_read_section(int nloops) +static void srcu_ref_perf_read_section(const int nloops) { int i; int idx; @@ -152,16 +165,29 @@ static void srcu_ref_perf_read_section(int nloops) } } +static void srcu_ref_perf_delay_section(const int nloops, const int ndelay) +{ + int i; + int idx; + + for (i = nloops; i >= 0; i--) { + idx = srcu_read_lock(srcu_ctlp); + udelay(ndelay); + srcu_read_unlock(srcu_ctlp, idx); + } +} + static struct ref_perf_ops srcu_ops = { .init = rcu_sync_perf_init, .readsection = srcu_ref_perf_read_section, + .delaysection = srcu_ref_perf_delay_section, .name = "srcu" }; // Definitions for reference count static atomic_t refcnt; -static void ref_perf_refcnt_section(const int nloops) +static void ref_refcnt_section(const int nloops) { int i; @@ -171,45 +197,69 @@ static void ref_perf_refcnt_section(const int nloops) } } +static void ref_refcnt_delay_section(const int nloops, const int ndelay) +{ + int i; + + for (i = nloops; i >= 0; i--) { + atomic_inc(&refcnt); + udelay(ndelay); + atomic_dec(&refcnt); + } +} + static struct ref_perf_ops refcnt_ops = { .init = rcu_sync_perf_init, - .readsection = ref_perf_refcnt_section, + .readsection = ref_refcnt_section, + .delaysection = ref_refcnt_delay_section, .name = "refcnt" }; // Definitions for rwlock static rwlock_t test_rwlock; -static void ref_perf_rwlock_init(void) +static void ref_rwlock_init(void) { rwlock_init(&test_rwlock); } -static void ref_perf_rwlock_section(const int nloops) +static void ref_rwlock_section(const int nloops) +{ + int i; + + for (i = nloops; i >= 0; i--) { + read_lock(&test_rwlock); + read_unlock(&test_rwlock); + } +} + +static void ref_rwlock_delay_section(const int nloops, const int ndelay) { int i; for (i = nloops; i >= 0; i--) { read_lock(&test_rwlock); + udelay(ndelay); read_unlock(&test_rwlock); } } static struct ref_perf_ops rwlock_ops = { - .init = ref_perf_rwlock_init, - .readsection = ref_perf_rwlock_section, + .init = ref_rwlock_init, + .readsection = ref_rwlock_section, + .delaysection = ref_rwlock_delay_section, .name = "rwlock" }; // Definitions for rwsem static struct rw_semaphore test_rwsem; -static void ref_perf_rwsem_init(void) +static void ref_rwsem_init(void) { init_rwsem(&test_rwsem); } -static void ref_perf_rwsem_section(const int nloops) +static void ref_rwsem_section(const int nloops) { int i; @@ -219,12 +269,32 @@ static void ref_perf_rwsem_section(const int nloops) } } +static void ref_rwsem_delay_section(const int nloops, const int ndelay) +{ + int i; + + for (i = nloops; i >= 0; i--) { + down_read(&test_rwsem); + udelay(ndelay); + up_read(&test_rwsem); + } +} + static struct ref_perf_ops rwsem_ops = { - .init = ref_perf_rwsem_init, - .readsection = ref_perf_rwsem_section, + .init = ref_rwsem_init, + .readsection = ref_rwsem_section, + .delaysection = ref_rwsem_delay_section, .name = "rwsem" }; +static void rcu_perf_one_reader(void) +{ + if (readdelay <= 0) + cur_ops->readsection(loops); + else + cur_ops->delaysection(loops, readdelay); +} + // Reader kthread. Repeatedly does empty RCU read-side // critical section, minimizing update-side interference. static int @@ -265,16 +335,16 @@ ref_perf_reader(void *arg) // To reduce noise, do an initial cache-warming invocation, check // in, and then keep warming until everyone has checked in. - cur_ops->readsection(loops); + rcu_perf_one_reader(); if (!atomic_dec_return(&n_warmedup)) while (atomic_read_acquire(&n_warmedup)) - cur_ops->readsection(loops); + rcu_perf_one_reader(); // Also keep interrupts disabled. This also has the effect // of preventing entries into slow path for rcu_read_unlock(). local_irq_save(flags); start = ktime_get_mono_fast_ns(); - cur_ops->readsection(loops); + rcu_perf_one_reader(); duration = ktime_get_mono_fast_ns() - start; local_irq_restore(flags); @@ -284,7 +354,7 @@ ref_perf_reader(void *arg) // everyone is done. if (!atomic_dec_return(&n_cooleddown)) while (atomic_read_acquire(&n_cooleddown)) - cur_ops->readsection(loops); + rcu_perf_one_reader(); if (atomic_dec_and_test(&nreaders_exp)) wake_up(&main_wq); @@ -449,8 +519,8 @@ static void ref_perf_print_module_parms(struct ref_perf_ops *cur_ops, const char *tag) { pr_alert("%s" PERF_FLAG - "--- %s: verbose=%d shutdown=%d holdoff=%d loops=%ld nreaders=%d nruns=%d\n", perf_type, tag, - verbose, shutdown, holdoff, loops, nreaders, nruns); + "--- %s: verbose=%d shutdown=%d holdoff=%d loops=%ld nreaders=%d nruns=%d readdelay=%d\n", perf_type, tag, + verbose, shutdown, holdoff, loops, nreaders, nruns, readdelay); } static void -- 2.9.5