// SPDX-License-Identifier: GPL-2.0+
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//
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// Scalability test comparing RCU vs other mechanisms
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// for acquiring references on objects.
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//
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// Copyright (C) Google, 2020.
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//
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// Author: Joel Fernandes <joel@joelfernandes.org>
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#define pr_fmt(fmt) fmt
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#include <linux/atomic.h>
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#include <linux/bitops.h>
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#include <linux/completion.h>
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#include <linux/cpu.h>
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#include <linux/delay.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/kthread.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/notifier.h>
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#include <linux/percpu.h>
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#include <linux/rcupdate.h>
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#include <linux/rcupdate_trace.h>
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#include <linux/reboot.h>
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#include <linux/sched.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/stat.h>
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#include <linux/srcu.h>
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#include <linux/slab.h>
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#include <linux/torture.h>
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#include <linux/types.h>
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#include "rcu.h"
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#define SCALE_FLAG "-ref-scale: "
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#define SCALEOUT(s, x...) \
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pr_alert("%s" SCALE_FLAG s, scale_type, ## x)
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#define VERBOSE_SCALEOUT(s, x...) \
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do { if (verbose) pr_alert("%s" SCALE_FLAG s, scale_type, ## x); } while (0)
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#define VERBOSE_SCALEOUT_ERRSTRING(s, x...) \
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do { if (verbose) pr_alert("%s" SCALE_FLAG "!!! " s, scale_type, ## x); } while (0)
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Joel Fernandes (Google) <joel@joelfernandes.org>");
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static char *scale_type = "rcu";
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module_param(scale_type, charp, 0444);
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MODULE_PARM_DESC(scale_type, "Type of test (rcu, srcu, refcnt, rwsem, rwlock.");
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torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
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// Wait until there are multiple CPUs before starting test.
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torture_param(int, holdoff, IS_BUILTIN(CONFIG_RCU_REF_SCALE_TEST) ? 10 : 0,
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"Holdoff time before test start (s)");
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// Number of loops per experiment, all readers execute operations concurrently.
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torture_param(long, loops, 10000, "Number of loops per experiment.");
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// Number of readers, with -1 defaulting to about 75% of the CPUs.
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torture_param(int, nreaders, -1, "Number of readers, -1 for 75% of CPUs.");
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// Number of runs.
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torture_param(int, nruns, 30, "Number of experiments to run.");
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// Reader delay in nanoseconds, 0 for no delay.
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torture_param(int, readdelay, 0, "Read-side delay in nanoseconds.");
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#ifdef MODULE
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# define REFSCALE_SHUTDOWN 0
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#else
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# define REFSCALE_SHUTDOWN 1
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#endif
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torture_param(bool, shutdown, REFSCALE_SHUTDOWN,
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"Shutdown at end of scalability tests.");
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struct reader_task {
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struct task_struct *task;
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int start_reader;
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wait_queue_head_t wq;
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u64 last_duration_ns;
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};
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static struct task_struct *shutdown_task;
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static wait_queue_head_t shutdown_wq;
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static struct task_struct *main_task;
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static wait_queue_head_t main_wq;
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static int shutdown_start;
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static struct reader_task *reader_tasks;
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// Number of readers that are part of the current experiment.
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static atomic_t nreaders_exp;
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// Use to wait for all threads to start.
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static atomic_t n_init;
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static atomic_t n_started;
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static atomic_t n_warmedup;
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static atomic_t n_cooleddown;
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// Track which experiment is currently running.
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static int exp_idx;
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// Operations vector for selecting different types of tests.
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struct ref_scale_ops {
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void (*init)(void);
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void (*cleanup)(void);
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void (*readsection)(const int nloops);
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void (*delaysection)(const int nloops, const int udl, const int ndl);
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const char *name;
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};
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static struct ref_scale_ops *cur_ops;
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static void un_delay(const int udl, const int ndl)
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{
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if (udl)
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udelay(udl);
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if (ndl)
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ndelay(ndl);
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}
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static void ref_rcu_read_section(const int nloops)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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rcu_read_lock();
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rcu_read_unlock();
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}
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}
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static void ref_rcu_delay_section(const int nloops, const int udl, const int ndl)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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rcu_read_lock();
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un_delay(udl, ndl);
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rcu_read_unlock();
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}
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}
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static void rcu_sync_scale_init(void)
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{
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}
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static struct ref_scale_ops rcu_ops = {
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.init = rcu_sync_scale_init,
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.readsection = ref_rcu_read_section,
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.delaysection = ref_rcu_delay_section,
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.name = "rcu"
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};
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// Definitions for SRCU ref scale testing.
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DEFINE_STATIC_SRCU(srcu_refctl_scale);
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static struct srcu_struct *srcu_ctlp = &srcu_refctl_scale;
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static void srcu_ref_scale_read_section(const int nloops)
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{
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int i;
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int idx;
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for (i = nloops; i >= 0; i--) {
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idx = srcu_read_lock(srcu_ctlp);
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srcu_read_unlock(srcu_ctlp, idx);
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}
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}
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static void srcu_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
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{
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int i;
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int idx;
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for (i = nloops; i >= 0; i--) {
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idx = srcu_read_lock(srcu_ctlp);
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un_delay(udl, ndl);
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srcu_read_unlock(srcu_ctlp, idx);
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}
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}
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static struct ref_scale_ops srcu_ops = {
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.init = rcu_sync_scale_init,
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.readsection = srcu_ref_scale_read_section,
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.delaysection = srcu_ref_scale_delay_section,
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.name = "srcu"
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};
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// Definitions for RCU Tasks ref scale testing: Empty read markers.
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// These definitions also work for RCU Rude readers.
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static void rcu_tasks_ref_scale_read_section(const int nloops)
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{
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int i;
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for (i = nloops; i >= 0; i--)
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continue;
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}
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static void rcu_tasks_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
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{
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int i;
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for (i = nloops; i >= 0; i--)
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un_delay(udl, ndl);
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}
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static struct ref_scale_ops rcu_tasks_ops = {
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.init = rcu_sync_scale_init,
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.readsection = rcu_tasks_ref_scale_read_section,
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.delaysection = rcu_tasks_ref_scale_delay_section,
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.name = "rcu-tasks"
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};
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// Definitions for RCU Tasks Trace ref scale testing.
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static void rcu_trace_ref_scale_read_section(const int nloops)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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rcu_read_lock_trace();
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rcu_read_unlock_trace();
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}
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}
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static void rcu_trace_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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rcu_read_lock_trace();
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un_delay(udl, ndl);
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rcu_read_unlock_trace();
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}
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}
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static struct ref_scale_ops rcu_trace_ops = {
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.init = rcu_sync_scale_init,
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.readsection = rcu_trace_ref_scale_read_section,
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.delaysection = rcu_trace_ref_scale_delay_section,
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.name = "rcu-trace"
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};
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// Definitions for reference count
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static atomic_t refcnt;
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static void ref_refcnt_section(const int nloops)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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atomic_inc(&refcnt);
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atomic_dec(&refcnt);
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}
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}
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static void ref_refcnt_delay_section(const int nloops, const int udl, const int ndl)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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atomic_inc(&refcnt);
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un_delay(udl, ndl);
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atomic_dec(&refcnt);
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}
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}
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static struct ref_scale_ops refcnt_ops = {
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.init = rcu_sync_scale_init,
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.readsection = ref_refcnt_section,
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.delaysection = ref_refcnt_delay_section,
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.name = "refcnt"
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};
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// Definitions for rwlock
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static rwlock_t test_rwlock;
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static void ref_rwlock_init(void)
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{
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rwlock_init(&test_rwlock);
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}
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static void ref_rwlock_section(const int nloops)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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read_lock(&test_rwlock);
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read_unlock(&test_rwlock);
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}
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}
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static void ref_rwlock_delay_section(const int nloops, const int udl, const int ndl)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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read_lock(&test_rwlock);
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un_delay(udl, ndl);
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read_unlock(&test_rwlock);
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}
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}
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static struct ref_scale_ops rwlock_ops = {
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.init = ref_rwlock_init,
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.readsection = ref_rwlock_section,
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.delaysection = ref_rwlock_delay_section,
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.name = "rwlock"
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};
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// Definitions for rwsem
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static struct rw_semaphore test_rwsem;
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static void ref_rwsem_init(void)
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{
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init_rwsem(&test_rwsem);
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}
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static void ref_rwsem_section(const int nloops)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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down_read(&test_rwsem);
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up_read(&test_rwsem);
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}
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}
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static void ref_rwsem_delay_section(const int nloops, const int udl, const int ndl)
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{
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int i;
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for (i = nloops; i >= 0; i--) {
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down_read(&test_rwsem);
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un_delay(udl, ndl);
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up_read(&test_rwsem);
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}
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}
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static struct ref_scale_ops rwsem_ops = {
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.init = ref_rwsem_init,
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.readsection = ref_rwsem_section,
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.delaysection = ref_rwsem_delay_section,
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.name = "rwsem"
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};
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static void rcu_scale_one_reader(void)
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{
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if (readdelay <= 0)
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cur_ops->readsection(loops);
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else
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cur_ops->delaysection(loops, readdelay / 1000, readdelay % 1000);
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}
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// Reader kthread. Repeatedly does empty RCU read-side
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// critical section, minimizing update-side interference.
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static int
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ref_scale_reader(void *arg)
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{
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unsigned long flags;
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long me = (long)arg;
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struct reader_task *rt = &(reader_tasks[me]);
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u64 start;
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s64 duration;
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VERBOSE_SCALEOUT("ref_scale_reader %ld: task started", me);
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set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
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set_user_nice(current, MAX_NICE);
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atomic_inc(&n_init);
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if (holdoff)
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schedule_timeout_interruptible(holdoff * HZ);
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repeat:
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VERBOSE_SCALEOUT("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, smp_processor_id());
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// Wait for signal that this reader can start.
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wait_event(rt->wq, (atomic_read(&nreaders_exp) && smp_load_acquire(&rt->start_reader)) ||
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torture_must_stop());
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if (torture_must_stop())
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goto end;
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// Make sure that the CPU is affinitized appropriately during testing.
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WARN_ON_ONCE(smp_processor_id() != me);
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WRITE_ONCE(rt->start_reader, 0);
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if (!atomic_dec_return(&n_started))
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while (atomic_read_acquire(&n_started))
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cpu_relax();
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VERBOSE_SCALEOUT("ref_scale_reader %ld: experiment %d started", me, exp_idx);
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// To reduce noise, do an initial cache-warming invocation, check
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// in, and then keep warming until everyone has checked in.
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rcu_scale_one_reader();
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if (!atomic_dec_return(&n_warmedup))
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while (atomic_read_acquire(&n_warmedup))
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rcu_scale_one_reader();
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// Also keep interrupts disabled. This also has the effect
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// of preventing entries into slow path for rcu_read_unlock().
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local_irq_save(flags);
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start = ktime_get_mono_fast_ns();
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rcu_scale_one_reader();
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duration = ktime_get_mono_fast_ns() - start;
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local_irq_restore(flags);
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rt->last_duration_ns = WARN_ON_ONCE(duration < 0) ? 0 : duration;
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// To reduce runtime-skew noise, do maintain-load invocations until
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// everyone is done.
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if (!atomic_dec_return(&n_cooleddown))
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while (atomic_read_acquire(&n_cooleddown))
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rcu_scale_one_reader();
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if (atomic_dec_and_test(&nreaders_exp))
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wake_up(&main_wq);
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VERBOSE_SCALEOUT("ref_scale_reader %ld: experiment %d ended, (readers remaining=%d)",
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me, exp_idx, atomic_read(&nreaders_exp));
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if (!torture_must_stop())
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goto repeat;
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end:
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torture_kthread_stopping("ref_scale_reader");
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return 0;
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}
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static void reset_readers(void)
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{
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int i;
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struct reader_task *rt;
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for (i = 0; i < nreaders; i++) {
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rt = &(reader_tasks[i]);
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rt->last_duration_ns = 0;
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}
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}
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// Print the results of each reader and return the sum of all their durations.
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static u64 process_durations(int n)
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{
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int i;
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struct reader_task *rt;
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char buf1[64];
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char *buf;
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u64 sum = 0;
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buf = kmalloc(128 + nreaders * 32, GFP_KERNEL);
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if (!buf)
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return 0;
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buf[0] = 0;
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sprintf(buf, "Experiment #%d (Format: <THREAD-NUM>:<Total loop time in ns>)",
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exp_idx);
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for (i = 0; i < n && !torture_must_stop(); i++) {
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rt = &(reader_tasks[i]);
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sprintf(buf1, "%d: %llu\t", i, rt->last_duration_ns);
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if (i % 5 == 0)
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strcat(buf, "\n");
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strcat(buf, buf1);
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sum += rt->last_duration_ns;
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}
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strcat(buf, "\n");
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SCALEOUT("%s\n", buf);
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kfree(buf);
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return sum;
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}
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// The main_func is the main orchestrator, it performs a bunch of
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// experiments. For every experiment, it orders all the readers
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// involved to start and waits for them to finish the experiment. It
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// then reads their timestamps and starts the next experiment. Each
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// experiment progresses from 1 concurrent reader to N of them at which
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// point all the timestamps are printed.
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static int main_func(void *arg)
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{
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bool errexit = false;
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int exp, r;
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char buf1[64];
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char *buf;
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u64 *result_avg;
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set_cpus_allowed_ptr(current, cpumask_of(nreaders % nr_cpu_ids));
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set_user_nice(current, MAX_NICE);
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VERBOSE_SCALEOUT("main_func task started");
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result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL);
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buf = kzalloc(64 + nruns * 32, GFP_KERNEL);
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if (!result_avg || !buf) {
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VERBOSE_SCALEOUT_ERRSTRING("out of memory");
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errexit = true;
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}
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if (holdoff)
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schedule_timeout_interruptible(holdoff * HZ);
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// Wait for all threads to start.
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atomic_inc(&n_init);
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while (atomic_read(&n_init) < nreaders + 1)
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schedule_timeout_uninterruptible(1);
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// Start exp readers up per experiment
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for (exp = 0; exp < nruns && !torture_must_stop(); exp++) {
|
if (errexit)
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break;
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if (torture_must_stop())
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goto end;
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|
reset_readers();
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atomic_set(&nreaders_exp, nreaders);
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atomic_set(&n_started, nreaders);
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atomic_set(&n_warmedup, nreaders);
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atomic_set(&n_cooleddown, nreaders);
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exp_idx = exp;
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for (r = 0; r < nreaders; r++) {
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smp_store_release(&reader_tasks[r].start_reader, 1);
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wake_up(&reader_tasks[r].wq);
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}
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VERBOSE_SCALEOUT("main_func: experiment started, waiting for %d readers",
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nreaders);
|
|
wait_event(main_wq,
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!atomic_read(&nreaders_exp) || torture_must_stop());
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|
VERBOSE_SCALEOUT("main_func: experiment ended");
|
|
if (torture_must_stop())
|
goto end;
|
|
result_avg[exp] = div_u64(1000 * process_durations(nreaders), nreaders * loops);
|
}
|
|
// Print the average of all experiments
|
SCALEOUT("END OF TEST. Calculating average duration per loop (nanoseconds)...\n");
|
|
if (!errexit) {
|
buf[0] = 0;
|
strcat(buf, "\n");
|
strcat(buf, "Runs\tTime(ns)\n");
|
}
|
|
for (exp = 0; exp < nruns; exp++) {
|
u64 avg;
|
u32 rem;
|
|
if (errexit)
|
break;
|
avg = div_u64_rem(result_avg[exp], 1000, &rem);
|
sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem);
|
strcat(buf, buf1);
|
}
|
|
if (!errexit)
|
SCALEOUT("%s", buf);
|
|
// This will shutdown everything including us.
|
if (shutdown) {
|
shutdown_start = 1;
|
wake_up(&shutdown_wq);
|
}
|
|
// Wait for torture to stop us
|
while (!torture_must_stop())
|
schedule_timeout_uninterruptible(1);
|
|
end:
|
torture_kthread_stopping("main_func");
|
kfree(result_avg);
|
kfree(buf);
|
return 0;
|
}
|
|
static void
|
ref_scale_print_module_parms(struct ref_scale_ops *cur_ops, const char *tag)
|
{
|
pr_alert("%s" SCALE_FLAG
|
"--- %s: verbose=%d shutdown=%d holdoff=%d loops=%ld nreaders=%d nruns=%d readdelay=%d\n", scale_type, tag,
|
verbose, shutdown, holdoff, loops, nreaders, nruns, readdelay);
|
}
|
|
static void
|
ref_scale_cleanup(void)
|
{
|
int i;
|
|
if (torture_cleanup_begin())
|
return;
|
|
if (!cur_ops) {
|
torture_cleanup_end();
|
return;
|
}
|
|
if (reader_tasks) {
|
for (i = 0; i < nreaders; i++)
|
torture_stop_kthread("ref_scale_reader",
|
reader_tasks[i].task);
|
}
|
kfree(reader_tasks);
|
|
torture_stop_kthread("main_task", main_task);
|
kfree(main_task);
|
|
// Do scale-type-specific cleanup operations.
|
if (cur_ops->cleanup != NULL)
|
cur_ops->cleanup();
|
|
torture_cleanup_end();
|
}
|
|
// Shutdown kthread. Just waits to be awakened, then shuts down system.
|
static int
|
ref_scale_shutdown(void *arg)
|
{
|
wait_event(shutdown_wq, shutdown_start);
|
|
smp_mb(); // Wake before output.
|
ref_scale_cleanup();
|
kernel_power_off();
|
|
return -EINVAL;
|
}
|
|
static int __init
|
ref_scale_init(void)
|
{
|
long i;
|
int firsterr = 0;
|
static struct ref_scale_ops *scale_ops[] = {
|
&rcu_ops, &srcu_ops, &rcu_trace_ops, &rcu_tasks_ops,
|
&refcnt_ops, &rwlock_ops, &rwsem_ops,
|
};
|
|
if (!torture_init_begin(scale_type, verbose))
|
return -EBUSY;
|
|
for (i = 0; i < ARRAY_SIZE(scale_ops); i++) {
|
cur_ops = scale_ops[i];
|
if (strcmp(scale_type, cur_ops->name) == 0)
|
break;
|
}
|
if (i == ARRAY_SIZE(scale_ops)) {
|
pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type);
|
pr_alert("rcu-scale types:");
|
for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
|
pr_cont(" %s", scale_ops[i]->name);
|
pr_cont("\n");
|
WARN_ON(!IS_MODULE(CONFIG_RCU_REF_SCALE_TEST));
|
firsterr = -EINVAL;
|
cur_ops = NULL;
|
goto unwind;
|
}
|
if (cur_ops->init)
|
cur_ops->init();
|
|
ref_scale_print_module_parms(cur_ops, "Start of test");
|
|
// Shutdown task
|
if (shutdown) {
|
init_waitqueue_head(&shutdown_wq);
|
firsterr = torture_create_kthread(ref_scale_shutdown, NULL,
|
shutdown_task);
|
if (firsterr)
|
goto unwind;
|
schedule_timeout_uninterruptible(1);
|
}
|
|
// Reader tasks (default to ~75% of online CPUs).
|
if (nreaders < 0)
|
nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2);
|
reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]),
|
GFP_KERNEL);
|
if (!reader_tasks) {
|
VERBOSE_SCALEOUT_ERRSTRING("out of memory");
|
firsterr = -ENOMEM;
|
goto unwind;
|
}
|
|
VERBOSE_SCALEOUT("Starting %d reader threads\n", nreaders);
|
|
for (i = 0; i < nreaders; i++) {
|
firsterr = torture_create_kthread(ref_scale_reader, (void *)i,
|
reader_tasks[i].task);
|
if (firsterr)
|
goto unwind;
|
|
init_waitqueue_head(&(reader_tasks[i].wq));
|
}
|
|
// Main Task
|
init_waitqueue_head(&main_wq);
|
firsterr = torture_create_kthread(main_func, NULL, main_task);
|
if (firsterr)
|
goto unwind;
|
|
torture_init_end();
|
return 0;
|
|
unwind:
|
torture_init_end();
|
ref_scale_cleanup();
|
return firsterr;
|
}
|
|
module_init(ref_scale_init);
|
module_exit(ref_scale_cleanup);
|
