diff options
Diffstat (limited to 'kernel/rcu/refscale.c')
| -rw-r--r-- | kernel/rcu/refscale.c | 1169 |
1 files changed, 1169 insertions, 0 deletions
diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c new file mode 100644 index 0000000000..91a0fd0d4d --- /dev/null +++ b/kernel/rcu/refscale.c @@ -0,0 +1,1169 @@ +// SPDX-License-Identifier: GPL-2.0+ +// +// Scalability test comparing RCU vs other mechanisms +// for acquiring references on objects. +// +// Copyright (C) Google, 2020. +// +// Author: Joel Fernandes <joel@joelfernandes.org> + +#define pr_fmt(fmt) fmt + +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/completion.h> +#include <linux/cpu.h> +#include <linux/delay.h> +#include <linux/err.h> +#include <linux/init.h> +#include <linux/interrupt.h> +#include <linux/kthread.h> +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/module.h> +#include <linux/moduleparam.h> +#include <linux/notifier.h> +#include <linux/percpu.h> +#include <linux/rcupdate.h> +#include <linux/rcupdate_trace.h> +#include <linux/reboot.h> +#include <linux/sched.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/stat.h> +#include <linux/srcu.h> +#include <linux/slab.h> +#include <linux/torture.h> +#include <linux/types.h> + +#include "rcu.h" + +#define SCALE_FLAG "-ref-scale: " + +#define SCALEOUT(s, x...) \ + pr_alert("%s" SCALE_FLAG s, scale_type, ## x) + +#define VERBOSE_SCALEOUT(s, x...) \ + do { \ + if (verbose) \ + pr_alert("%s" SCALE_FLAG s "\n", scale_type, ## x); \ + } while (0) + +static atomic_t verbose_batch_ctr; + +#define VERBOSE_SCALEOUT_BATCH(s, x...) \ +do { \ + if (verbose && \ + (verbose_batched <= 0 || \ + !(atomic_inc_return(&verbose_batch_ctr) % verbose_batched))) { \ + schedule_timeout_uninterruptible(1); \ + pr_alert("%s" SCALE_FLAG s "\n", scale_type, ## x); \ + } \ +} while (0) + +#define SCALEOUT_ERRSTRING(s, x...) pr_alert("%s" SCALE_FLAG "!!! " s "\n", scale_type, ## x) + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Joel Fernandes (Google) <joel@joelfernandes.org>"); + +static char *scale_type = "rcu"; +module_param(scale_type, charp, 0444); +MODULE_PARM_DESC(scale_type, "Type of test (rcu, srcu, refcnt, rwsem, rwlock."); + +torture_param(int, verbose, 0, "Enable verbose debugging printk()s"); +torture_param(int, verbose_batched, 0, "Batch verbose debugging printk()s"); + +// Wait until there are multiple CPUs before starting test. +torture_param(int, holdoff, IS_BUILTIN(CONFIG_RCU_REF_SCALE_TEST) ? 10 : 0, + "Holdoff time before test start (s)"); +// Number of typesafe_lookup structures, that is, the degree of concurrency. +torture_param(long, lookup_instances, 0, "Number of typesafe_lookup structures."); +// Number of loops per experiment, all readers execute operations concurrently. +torture_param(long, loops, 10000, "Number of loops per experiment."); +// Number of readers, with -1 defaulting to about 75% of the CPUs. +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."); + +#ifdef MODULE +# define REFSCALE_SHUTDOWN 0 +#else +# define REFSCALE_SHUTDOWN 1 +#endif + +torture_param(bool, shutdown, REFSCALE_SHUTDOWN, + "Shutdown at end of scalability tests."); + +struct reader_task { + struct task_struct *task; + int start_reader; + wait_queue_head_t wq; + u64 last_duration_ns; +}; + +static struct task_struct *shutdown_task; +static wait_queue_head_t shutdown_wq; + +static struct task_struct *main_task; +static wait_queue_head_t main_wq; +static int shutdown_start; + +static struct reader_task *reader_tasks; + +// Number of readers that are part of the current experiment. +static atomic_t nreaders_exp; + +// Use to wait for all threads to start. +static atomic_t n_init; +static atomic_t n_started; +static atomic_t n_warmedup; +static atomic_t n_cooleddown; + +// Track which experiment is currently running. +static int exp_idx; + +// Operations vector for selecting different types of tests. +struct ref_scale_ops { + bool (*init)(void); + void (*cleanup)(void); + void (*readsection)(const int nloops); + void (*delaysection)(const int nloops, const int udl, const int ndl); + const char *name; +}; + +static struct ref_scale_ops *cur_ops; + +static void un_delay(const int udl, const int ndl) +{ + if (udl) + udelay(udl); + if (ndl) + ndelay(ndl); +} + +static void ref_rcu_read_section(const int nloops) +{ + int i; + + for (i = nloops; i >= 0; i--) { + rcu_read_lock(); + rcu_read_unlock(); + } +} + +static void ref_rcu_delay_section(const int nloops, const int udl, const int ndl) +{ + int i; + + for (i = nloops; i >= 0; i--) { + rcu_read_lock(); + un_delay(udl, ndl); + rcu_read_unlock(); + } +} + +static bool rcu_sync_scale_init(void) +{ + return true; +} + +static struct ref_scale_ops rcu_ops = { + .init = rcu_sync_scale_init, + .readsection = ref_rcu_read_section, + .delaysection = ref_rcu_delay_section, + .name = "rcu" +}; + +// Definitions for SRCU ref scale testing. +DEFINE_STATIC_SRCU(srcu_refctl_scale); +static struct srcu_struct *srcu_ctlp = &srcu_refctl_scale; + +static void srcu_ref_scale_read_section(const int nloops) +{ + int i; + int idx; + + for (i = nloops; i >= 0; i--) { + idx = srcu_read_lock(srcu_ctlp); + srcu_read_unlock(srcu_ctlp, idx); + } +} + +static void srcu_ref_scale_delay_section(const int nloops, const int udl, const int ndl) +{ + int i; + int idx; + + for (i = nloops; i >= 0; i--) { + idx = srcu_read_lock(srcu_ctlp); + un_delay(udl, ndl); + srcu_read_unlock(srcu_ctlp, idx); + } +} + +static struct ref_scale_ops srcu_ops = { + .init = rcu_sync_scale_init, + .readsection = srcu_ref_scale_read_section, + .delaysection = srcu_ref_scale_delay_section, + .name = "srcu" +}; + +#ifdef CONFIG_TASKS_RCU + +// Definitions for RCU Tasks ref scale testing: Empty read markers. +// These definitions also work for RCU Rude readers. +static void rcu_tasks_ref_scale_read_section(const int nloops) +{ + int i; + + for (i = nloops; i >= 0; i--) + continue; +} + +static void rcu_tasks_ref_scale_delay_section(const int nloops, const int udl, const int ndl) +{ + int i; + + for (i = nloops; i >= 0; i--) + un_delay(udl, ndl); +} + +static struct ref_scale_ops rcu_tasks_ops = { + .init = rcu_sync_scale_init, + .readsection = rcu_tasks_ref_scale_read_section, + .delaysection = rcu_tasks_ref_scale_delay_section, + .name = "rcu-tasks" +}; + +#define RCU_TASKS_OPS &rcu_tasks_ops, + +#else // #ifdef CONFIG_TASKS_RCU + +#define RCU_TASKS_OPS + +#endif // #else // #ifdef CONFIG_TASKS_RCU + +#ifdef CONFIG_TASKS_TRACE_RCU + +// Definitions for RCU Tasks Trace ref scale testing. +static void rcu_trace_ref_scale_read_section(const int nloops) +{ + int i; + + for (i = nloops; i >= 0; i--) { + rcu_read_lock_trace(); + rcu_read_unlock_trace(); + } +} + +static void rcu_trace_ref_scale_delay_section(const int nloops, const int udl, const int ndl) +{ + int i; + + for (i = nloops; i >= 0; i--) { + rcu_read_lock_trace(); + un_delay(udl, ndl); + rcu_read_unlock_trace(); + } +} + +static struct ref_scale_ops rcu_trace_ops = { + .init = rcu_sync_scale_init, + .readsection = rcu_trace_ref_scale_read_section, + .delaysection = rcu_trace_ref_scale_delay_section, + .name = "rcu-trace" +}; + +#define RCU_TRACE_OPS &rcu_trace_ops, + +#else // #ifdef CONFIG_TASKS_TRACE_RCU + +#define RCU_TRACE_OPS + +#endif // #else // #ifdef CONFIG_TASKS_TRACE_RCU + +// Definitions for reference count +static atomic_t refcnt; + +static void ref_refcnt_section(const int nloops) +{ + int i; + + for (i = nloops; i >= 0; i--) { + atomic_inc(&refcnt); + atomic_dec(&refcnt); + } +} + +static void ref_refcnt_delay_section(const int nloops, const int udl, const int ndl) +{ + int i; + + for (i = nloops; i >= 0; i--) { + atomic_inc(&refcnt); + un_delay(udl, ndl); + atomic_dec(&refcnt); + } +} + +static struct ref_scale_ops refcnt_ops = { + .init = rcu_sync_scale_init, + .readsection = ref_refcnt_section, + .delaysection = ref_refcnt_delay_section, + .name = "refcnt" +}; + +// Definitions for rwlock +static rwlock_t test_rwlock; + +static bool ref_rwlock_init(void) +{ + rwlock_init(&test_rwlock); + return true; +} + +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 udl, const int ndl) +{ + int i; + + for (i = nloops; i >= 0; i--) { + read_lock(&test_rwlock); + un_delay(udl, ndl); + read_unlock(&test_rwlock); + } +} + +static struct ref_scale_ops rwlock_ops = { + .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 bool ref_rwsem_init(void) +{ + init_rwsem(&test_rwsem); + return true; +} + +static void ref_rwsem_section(const int nloops) +{ + int i; + + for (i = nloops; i >= 0; i--) { + down_read(&test_rwsem); + up_read(&test_rwsem); + } +} + +static void ref_rwsem_delay_section(const int nloops, const int udl, const int ndl) +{ + int i; + + for (i = nloops; i >= 0; i--) { + down_read(&test_rwsem); + un_delay(udl, ndl); + up_read(&test_rwsem); + } +} + +static struct ref_scale_ops rwsem_ops = { + .init = ref_rwsem_init, + .readsection = ref_rwsem_section, + .delaysection = ref_rwsem_delay_section, + .name = "rwsem" +}; + +// Definitions for global spinlock +static DEFINE_RAW_SPINLOCK(test_lock); + +static void ref_lock_section(const int nloops) +{ + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) { + raw_spin_lock(&test_lock); + raw_spin_unlock(&test_lock); + } + preempt_enable(); +} + +static void ref_lock_delay_section(const int nloops, const int udl, const int ndl) +{ + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) { + raw_spin_lock(&test_lock); + un_delay(udl, ndl); + raw_spin_unlock(&test_lock); + } + preempt_enable(); +} + +static struct ref_scale_ops lock_ops = { + .readsection = ref_lock_section, + .delaysection = ref_lock_delay_section, + .name = "lock" +}; + +// Definitions for global irq-save spinlock + +static void ref_lock_irq_section(const int nloops) +{ + unsigned long flags; + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) { + raw_spin_lock_irqsave(&test_lock, flags); + raw_spin_unlock_irqrestore(&test_lock, flags); + } + preempt_enable(); +} + +static void ref_lock_irq_delay_section(const int nloops, const int udl, const int ndl) +{ + unsigned long flags; + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) { + raw_spin_lock_irqsave(&test_lock, flags); + un_delay(udl, ndl); + raw_spin_unlock_irqrestore(&test_lock, flags); + } + preempt_enable(); +} + +static struct ref_scale_ops lock_irq_ops = { + .readsection = ref_lock_irq_section, + .delaysection = ref_lock_irq_delay_section, + .name = "lock-irq" +}; + +// Definitions acquire-release. +static DEFINE_PER_CPU(unsigned long, test_acqrel); + +static void ref_acqrel_section(const int nloops) +{ + unsigned long x; + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) { + x = smp_load_acquire(this_cpu_ptr(&test_acqrel)); + smp_store_release(this_cpu_ptr(&test_acqrel), x + 1); + } + preempt_enable(); +} + +static void ref_acqrel_delay_section(const int nloops, const int udl, const int ndl) +{ + unsigned long x; + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) { + x = smp_load_acquire(this_cpu_ptr(&test_acqrel)); + un_delay(udl, ndl); + smp_store_release(this_cpu_ptr(&test_acqrel), x + 1); + } + preempt_enable(); +} + +static struct ref_scale_ops acqrel_ops = { + .readsection = ref_acqrel_section, + .delaysection = ref_acqrel_delay_section, + .name = "acqrel" +}; + +static volatile u64 stopopts; + +static void ref_clock_section(const int nloops) +{ + u64 x = 0; + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) + x += ktime_get_real_fast_ns(); + preempt_enable(); + stopopts = x; +} + +static void ref_clock_delay_section(const int nloops, const int udl, const int ndl) +{ + u64 x = 0; + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) { + x += ktime_get_real_fast_ns(); + un_delay(udl, ndl); + } + preempt_enable(); + stopopts = x; +} + +static struct ref_scale_ops clock_ops = { + .readsection = ref_clock_section, + .delaysection = ref_clock_delay_section, + .name = "clock" +}; + +static void ref_jiffies_section(const int nloops) +{ + u64 x = 0; + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) + x += jiffies; + preempt_enable(); + stopopts = x; +} + +static void ref_jiffies_delay_section(const int nloops, const int udl, const int ndl) +{ + u64 x = 0; + int i; + + preempt_disable(); + for (i = nloops; i >= 0; i--) { + x += jiffies; + un_delay(udl, ndl); + } + preempt_enable(); + stopopts = x; +} + +static struct ref_scale_ops jiffies_ops = { + .readsection = ref_jiffies_section, + .delaysection = ref_jiffies_delay_section, + .name = "jiffies" +}; + +//////////////////////////////////////////////////////////////////////// +// +// Methods leveraging SLAB_TYPESAFE_BY_RCU. +// + +// Item to look up in a typesafe manner. Array of pointers to these. +struct refscale_typesafe { + atomic_t rts_refctr; // Used by all flavors + spinlock_t rts_lock; + seqlock_t rts_seqlock; + unsigned int a; + unsigned int b; +}; + +static struct kmem_cache *typesafe_kmem_cachep; +static struct refscale_typesafe **rtsarray; +static long rtsarray_size; +static DEFINE_TORTURE_RANDOM_PERCPU(refscale_rand); +static bool (*rts_acquire)(struct refscale_typesafe *rtsp, unsigned int *start); +static bool (*rts_release)(struct refscale_typesafe *rtsp, unsigned int start); + +// Conditionally acquire an explicit in-structure reference count. +static bool typesafe_ref_acquire(struct refscale_typesafe *rtsp, unsigned int *start) +{ + return atomic_inc_not_zero(&rtsp->rts_refctr); +} + +// Unconditionally release an explicit in-structure reference count. +static bool typesafe_ref_release(struct refscale_typesafe *rtsp, unsigned int start) +{ + if (!atomic_dec_return(&rtsp->rts_refctr)) { + WRITE_ONCE(rtsp->a, rtsp->a + 1); + kmem_cache_free(typesafe_kmem_cachep, rtsp); + } + return true; +} + +// Unconditionally acquire an explicit in-structure spinlock. +static bool typesafe_lock_acquire(struct refscale_typesafe *rtsp, unsigned int *start) +{ + spin_lock(&rtsp->rts_lock); + return true; +} + +// Unconditionally release an explicit in-structure spinlock. +static bool typesafe_lock_release(struct refscale_typesafe *rtsp, unsigned int start) +{ + spin_unlock(&rtsp->rts_lock); + return true; +} + +// Unconditionally acquire an explicit in-structure sequence lock. +static bool typesafe_seqlock_acquire(struct refscale_typesafe *rtsp, unsigned int *start) +{ + *start = read_seqbegin(&rtsp->rts_seqlock); + return true; +} + +// Conditionally release an explicit in-structure sequence lock. Return +// true if this release was successful, that is, if no retry is required. +static bool typesafe_seqlock_release(struct refscale_typesafe *rtsp, unsigned int start) +{ + return !read_seqretry(&rtsp->rts_seqlock, start); +} + +// Do a read-side critical section with the specified delay in +// microseconds and nanoseconds inserted so as to increase probability +// of failure. +static void typesafe_delay_section(const int nloops, const int udl, const int ndl) +{ + unsigned int a; + unsigned int b; + int i; + long idx; + struct refscale_typesafe *rtsp; + unsigned int start; + + for (i = nloops; i >= 0; i--) { + preempt_disable(); + idx = torture_random(this_cpu_ptr(&refscale_rand)) % rtsarray_size; + preempt_enable(); +retry: + rcu_read_lock(); + rtsp = rcu_dereference(rtsarray[idx]); + a = READ_ONCE(rtsp->a); + if (!rts_acquire(rtsp, &start)) { + rcu_read_unlock(); + goto retry; + } + if (a != READ_ONCE(rtsp->a)) { + (void)rts_release(rtsp, start); + rcu_read_unlock(); + goto retry; + } + un_delay(udl, ndl); + // Remember, seqlock read-side release can fail. + if (!rts_release(rtsp, start)) { + rcu_read_unlock(); + goto retry; + } + b = READ_ONCE(rtsp->a); + WARN_ONCE(a != b, "Re-read of ->a changed from %u to %u.\n", a, b); + b = rtsp->b; + rcu_read_unlock(); + WARN_ON_ONCE(a * a != b); + } +} + +// Because the acquisition and release methods are expensive, there +// is no point in optimizing away the un_delay() function's two checks. +// Thus simply define typesafe_read_section() as a simple wrapper around +// typesafe_delay_section(). +static void typesafe_read_section(const int nloops) +{ + typesafe_delay_section(nloops, 0, 0); +} + +// Allocate and initialize one refscale_typesafe structure. +static struct refscale_typesafe *typesafe_alloc_one(void) +{ + struct refscale_typesafe *rtsp; + + rtsp = kmem_cache_alloc(typesafe_kmem_cachep, GFP_KERNEL); + if (!rtsp) + return NULL; + atomic_set(&rtsp->rts_refctr, 1); + WRITE_ONCE(rtsp->a, rtsp->a + 1); + WRITE_ONCE(rtsp->b, rtsp->a * rtsp->a); + return rtsp; +} + +// Slab-allocator constructor for refscale_typesafe structures created +// out of a new slab of system memory. +static void refscale_typesafe_ctor(void *rtsp_in) +{ + struct refscale_typesafe *rtsp = rtsp_in; + + spin_lock_init(&rtsp->rts_lock); + seqlock_init(&rtsp->rts_seqlock); + preempt_disable(); + rtsp->a = torture_random(this_cpu_ptr(&refscale_rand)); + preempt_enable(); +} + +static struct ref_scale_ops typesafe_ref_ops; +static struct ref_scale_ops typesafe_lock_ops; +static struct ref_scale_ops typesafe_seqlock_ops; + +// Initialize for a typesafe test. +static bool typesafe_init(void) +{ + long idx; + long si = lookup_instances; + + typesafe_kmem_cachep = kmem_cache_create("refscale_typesafe", + sizeof(struct refscale_typesafe), sizeof(void *), + SLAB_TYPESAFE_BY_RCU, refscale_typesafe_ctor); + if (!typesafe_kmem_cachep) + return false; + if (si < 0) + si = -si * nr_cpu_ids; + else if (si == 0) + si = nr_cpu_ids; + rtsarray_size = si; + rtsarray = kcalloc(si, sizeof(*rtsarray), GFP_KERNEL); + if (!rtsarray) + return false; + for (idx = 0; idx < rtsarray_size; idx++) { + rtsarray[idx] = typesafe_alloc_one(); + if (!rtsarray[idx]) + return false; + } + if (cur_ops == &typesafe_ref_ops) { + rts_acquire = typesafe_ref_acquire; + rts_release = typesafe_ref_release; + } else if (cur_ops == &typesafe_lock_ops) { + rts_acquire = typesafe_lock_acquire; + rts_release = typesafe_lock_release; + } else if (cur_ops == &typesafe_seqlock_ops) { + rts_acquire = typesafe_seqlock_acquire; + rts_release = typesafe_seqlock_release; + } else { + WARN_ON_ONCE(1); + return false; + } + return true; +} + +// Clean up after a typesafe test. +static void typesafe_cleanup(void) +{ + long idx; + + if (rtsarray) { + for (idx = 0; idx < rtsarray_size; idx++) + kmem_cache_free(typesafe_kmem_cachep, rtsarray[idx]); + kfree(rtsarray); + rtsarray = NULL; + rtsarray_size = 0; + } + kmem_cache_destroy(typesafe_kmem_cachep); + typesafe_kmem_cachep = NULL; + rts_acquire = NULL; + rts_release = NULL; +} + +// The typesafe_init() function distinguishes these structures by address. +static struct ref_scale_ops typesafe_ref_ops = { + .init = typesafe_init, + .cleanup = typesafe_cleanup, + .readsection = typesafe_read_section, + .delaysection = typesafe_delay_section, + .name = "typesafe_ref" +}; + +static struct ref_scale_ops typesafe_lock_ops = { + .init = typesafe_init, + .cleanup = typesafe_cleanup, + .readsection = typesafe_read_section, + .delaysection = typesafe_delay_section, + .name = "typesafe_lock" +}; + +static struct ref_scale_ops typesafe_seqlock_ops = { + .init = typesafe_init, + .cleanup = typesafe_cleanup, + .readsection = typesafe_read_section, + .delaysection = typesafe_delay_section, + .name = "typesafe_seqlock" +}; + +static void rcu_scale_one_reader(void) +{ + if (readdelay <= 0) + cur_ops->readsection(loops); + else + cur_ops->delaysection(loops, readdelay / 1000, readdelay % 1000); +} + +// Reader kthread. Repeatedly does empty RCU read-side +// critical section, minimizing update-side interference. +static int +ref_scale_reader(void *arg) +{ + unsigned long flags; + long me = (long)arg; + struct reader_task *rt = &(reader_tasks[me]); + u64 start; + s64 duration; + + VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: task started", me); + WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids))); + set_user_nice(current, MAX_NICE); + atomic_inc(&n_init); + if (holdoff) + schedule_timeout_interruptible(holdoff * HZ); +repeat: + VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, raw_smp_processor_id()); + + // Wait for signal that this reader can start. + wait_event(rt->wq, (atomic_read(&nreaders_exp) && smp_load_acquire(&rt->start_reader)) || + torture_must_stop()); + + if (torture_must_stop()) + goto end; + + // Make sure that the CPU is affinitized appropriately during testing. + WARN_ON_ONCE(raw_smp_processor_id() != me); + + WRITE_ONCE(rt->start_reader, 0); + if (!atomic_dec_return(&n_started)) + while (atomic_read_acquire(&n_started)) + cpu_relax(); + + VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: experiment %d started", me, exp_idx); + + + // To reduce noise, do an initial cache-warming invocation, check + // in, and then keep warming until everyone has checked in. + rcu_scale_one_reader(); + if (!atomic_dec_return(&n_warmedup)) + while (atomic_read_acquire(&n_warmedup)) + rcu_scale_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(); + + rcu_scale_one_reader(); + + duration = ktime_get_mono_fast_ns() - start; + local_irq_restore(flags); + + rt->last_duration_ns = WARN_ON_ONCE(duration < 0) ? 0 : duration; + // To reduce runtime-skew noise, do maintain-load invocations until + // everyone is done. + if (!atomic_dec_return(&n_cooleddown)) + while (atomic_read_acquire(&n_cooleddown)) + rcu_scale_one_reader(); + + if (atomic_dec_and_test(&nreaders_exp)) + wake_up(&main_wq); + + VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: experiment %d ended, (readers remaining=%d)", + me, exp_idx, atomic_read(&nreaders_exp)); + + if (!torture_must_stop()) + goto repeat; +end: + torture_kthread_stopping("ref_scale_reader"); + return 0; +} + +static void reset_readers(void) +{ + int i; + struct reader_task *rt; + + for (i = 0; i < nreaders; i++) { + rt = &(reader_tasks[i]); + + rt->last_duration_ns = 0; + } +} + +// Print the results of each reader and return the sum of all their durations. +static u64 process_durations(int n) +{ + int i; + struct reader_task *rt; + char buf1[64]; + char *buf; + u64 sum = 0; + + buf = kmalloc(800 + 64, GFP_KERNEL); + if (!buf) + return 0; + buf[0] = 0; + sprintf(buf, "Experiment #%d (Format: <THREAD-NUM>:<Total loop time in ns>)", + exp_idx); + + for (i = 0; i < n && !torture_must_stop(); i++) { + rt = &(reader_tasks[i]); + sprintf(buf1, "%d: %llu\t", i, rt->last_duration_ns); + + if (i % 5 == 0) + strcat(buf, "\n"); + if (strlen(buf) >= 800) { + pr_alert("%s", buf); + buf[0] = 0; + } + strcat(buf, buf1); + + sum += rt->last_duration_ns; + } + pr_alert("%s\n", buf); + + kfree(buf); + return sum; +} + +// The main_func is the main orchestrator, it performs a bunch of +// experiments. For every experiment, it orders all the readers +// involved to start and waits for them to finish the experiment. It +// then reads their timestamps and starts the next experiment. Each +// experiment progresses from 1 concurrent reader to N of them at which +// point all the timestamps are printed. +static int main_func(void *arg) +{ + int exp, r; + char buf1[64]; + char *buf; + u64 *result_avg; + + set_cpus_allowed_ptr(current, cpumask_of(nreaders % nr_cpu_ids)); + set_user_nice(current, MAX_NICE); + + VERBOSE_SCALEOUT("main_func task started"); + result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL); + buf = kzalloc(800 + 64, GFP_KERNEL); + if (!result_avg || !buf) { + SCALEOUT_ERRSTRING("out of memory"); + goto oom_exit; + } + if (holdoff) + schedule_timeout_interruptible(holdoff * HZ); + + // Wait for all threads to start. + atomic_inc(&n_init); + while (atomic_read(&n_init) < nreaders + 1) + schedule_timeout_uninterruptible(1); + + // Start exp readers up per experiment + for (exp = 0; exp < nruns && !torture_must_stop(); exp++) { + if (torture_must_stop()) + goto end; + + reset_readers(); + atomic_set(&nreaders_exp, nreaders); + atomic_set(&n_started, nreaders); + atomic_set(&n_warmedup, nreaders); + atomic_set(&n_cooleddown, nreaders); + + exp_idx = exp; + + for (r = 0; r < nreaders; r++) { + smp_store_release(&reader_tasks[r].start_reader, 1); + wake_up(&reader_tasks[r].wq); + } + + VERBOSE_SCALEOUT("main_func: experiment started, waiting for %d readers", + nreaders); + + wait_event(main_wq, + !atomic_read(&nreaders_exp) || torture_must_stop()); + + 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"); + + pr_alert("Runs\tTime(ns)\n"); + for (exp = 0; exp < nruns; exp++) { + u64 avg; + u32 rem; + + avg = div_u64_rem(result_avg[exp], 1000, &rem); + sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem); + strcat(buf, buf1); + if (strlen(buf) >= 800) { + pr_alert("%s", buf); + buf[0] = 0; + } + } + + pr_alert("%s", buf); + +oom_exit: + // 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_idle(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, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops, &jiffies_ops, + &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_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"); + firsterr = -EINVAL; + cur_ops = NULL; + goto unwind; + } + if (cur_ops->init) + if (!cur_ops->init()) { + firsterr = -EUCLEAN; + goto unwind; + } + + 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 (torture_init_error(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); + if (WARN_ONCE(loops <= 0, "%s: loops = %ld, adjusted to 1\n", __func__, loops)) + loops = 1; + if (WARN_ONCE(nreaders <= 0, "%s: nreaders = %d, adjusted to 1\n", __func__, nreaders)) + nreaders = 1; + if (WARN_ONCE(nruns <= 0, "%s: nruns = %d, adjusted to 1\n", __func__, nruns)) + nruns = 1; + reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]), + GFP_KERNEL); + if (!reader_tasks) { + SCALEOUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + + VERBOSE_SCALEOUT("Starting %d reader threads", nreaders); + + for (i = 0; i < nreaders; i++) { + init_waitqueue_head(&reader_tasks[i].wq); + firsterr = torture_create_kthread(ref_scale_reader, (void *)i, + reader_tasks[i].task); + if (torture_init_error(firsterr)) + goto unwind; + } + + // Main Task + init_waitqueue_head(&main_wq); + firsterr = torture_create_kthread(main_func, NULL, main_task); + if (torture_init_error(firsterr)) + goto unwind; + + torture_init_end(); + return 0; + +unwind: + torture_init_end(); + ref_scale_cleanup(); + if (shutdown) { + WARN_ON(!IS_MODULE(CONFIG_RCU_REF_SCALE_TEST)); + kernel_power_off(); + } + return firsterr; +} + +module_init(ref_scale_init); +module_exit(ref_scale_cleanup); |