#include <linux/cacheinfo.h>
#include <linux/cpu.h>
#include <linux/cpumask.h>
+#include <linux/debugfs.h>
#include <linux/kthread.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
#include <asm/intel_rdt_sched.h>
#include "intel_rdt.h"
+#define CREATE_TRACE_POINTS
+#include "intel_rdt_pseudo_lock_event.h"
+
/*
* MSR_MISC_FEATURE_CONTROL register enables the modification of hardware
* prefetcher state. Details about this register can be found in the MSR
plr->d->plr = NULL;
plr->d = NULL;
plr->cbm = 0;
+ plr->debugfs_dir = NULL;
}
/**
return ret;
}
+/**
+ * measure_cycles_lat_fn - Measure cycle latency to read pseudo-locked memory
+ * @_plr: pseudo-lock region to measure
+ *
+ * There is no deterministic way to test if a memory region is cached. One
+ * way is to measure how long it takes to read the memory, the speed of
+ * access is a good way to learn how close to the cpu the data was. Even
+ * more, if the prefetcher is disabled and the memory is read at a stride
+ * of half the cache line, then a cache miss will be easy to spot since the
+ * read of the first half would be significantly slower than the read of
+ * the second half.
+ *
+ * Return: 0. Waiter on waitqueue will be woken on completion.
+ */
+static int measure_cycles_lat_fn(void *_plr)
+{
+ struct pseudo_lock_region *plr = _plr;
+ unsigned long i;
+ u64 start, end;
+#ifdef CONFIG_KASAN
+ /*
+ * The registers used for local register variables are also used
+ * when KASAN is active. When KASAN is active we use a regular
+ * variable to ensure we always use a valid pointer to access memory.
+ * The cost is that accessing this pointer, which could be in
+ * cache, will be included in the measurement of memory read latency.
+ */
+ void *mem_r;
+#else
+#ifdef CONFIG_X86_64
+ register void *mem_r asm("rbx");
+#else
+ register void *mem_r asm("ebx");
+#endif /* CONFIG_X86_64 */
+#endif /* CONFIG_KASAN */
+
+ local_irq_disable();
+ /*
+ * The wrmsr call may be reordered with the assignment below it.
+ * Call wrmsr as directly as possible to avoid tracing clobbering
+ * local register variable used for memory pointer.
+ */
+ __wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
+ mem_r = plr->kmem;
+ /*
+ * Dummy execute of the time measurement to load the needed
+ * instructions into the L1 instruction cache.
+ */
+ start = rdtsc_ordered();
+ for (i = 0; i < plr->size; i += 32) {
+ start = rdtsc_ordered();
+ asm volatile("mov (%0,%1,1), %%eax\n\t"
+ :
+ : "r" (mem_r), "r" (i)
+ : "%eax", "memory");
+ end = rdtsc_ordered();
+ trace_pseudo_lock_mem_latency((u32)(end - start));
+ }
+ wrmsr(MSR_MISC_FEATURE_CONTROL, 0x0, 0x0);
+ local_irq_enable();
+ plr->thread_done = 1;
+ wake_up_interruptible(&plr->lock_thread_wq);
+ return 0;
+}
+
+/**
+ * pseudo_lock_measure_cycles - Trigger latency measure to pseudo-locked region
+ *
+ * The measurement of latency to access a pseudo-locked region should be
+ * done from a cpu that is associated with that pseudo-locked region.
+ * Determine which cpu is associated with this region and start a thread on
+ * that cpu to perform the measurement, wait for that thread to complete.
+ *
+ * Return: 0 on success, <0 on failure
+ */
+static int pseudo_lock_measure_cycles(struct rdtgroup *rdtgrp)
+{
+ struct pseudo_lock_region *plr = rdtgrp->plr;
+ struct task_struct *thread;
+ unsigned int cpu;
+ int ret;
+
+ cpus_read_lock();
+ mutex_lock(&rdtgroup_mutex);
+
+ if (rdtgrp->flags & RDT_DELETED) {
+ ret = -ENODEV;
+ goto out;
+ }
+
+ plr->thread_done = 0;
+ cpu = cpumask_first(&plr->d->cpu_mask);
+ if (!cpu_online(cpu)) {
+ ret = -ENODEV;
+ goto out;
+ }
+
+ thread = kthread_create_on_node(measure_cycles_lat_fn, plr,
+ cpu_to_node(cpu),
+ "pseudo_lock_measure/%u", cpu);
+ if (IS_ERR(thread)) {
+ ret = PTR_ERR(thread);
+ goto out;
+ }
+ kthread_bind(thread, cpu);
+ wake_up_process(thread);
+
+ ret = wait_event_interruptible(plr->lock_thread_wq,
+ plr->thread_done == 1);
+ if (ret < 0)
+ goto out;
+
+ ret = 0;
+
+out:
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+ return ret;
+}
+
+static ssize_t pseudo_lock_measure_trigger(struct file *file,
+ const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct rdtgroup *rdtgrp = file->private_data;
+ size_t buf_size;
+ char buf[32];
+ int ret;
+ bool bv;
+
+ buf_size = min(count, (sizeof(buf) - 1));
+ if (copy_from_user(buf, user_buf, buf_size))
+ return -EFAULT;
+
+ buf[buf_size] = '\0';
+ ret = strtobool(buf, &bv);
+ if (ret == 0 && bv) {
+ ret = debugfs_file_get(file->f_path.dentry);
+ if (ret)
+ return ret;
+ ret = pseudo_lock_measure_cycles(rdtgrp);
+ if (ret == 0)
+ ret = count;
+ debugfs_file_put(file->f_path.dentry);
+ }
+
+ return ret;
+}
+
+static const struct file_operations pseudo_measure_fops = {
+ .write = pseudo_lock_measure_trigger,
+ .open = simple_open,
+ .llseek = default_llseek,
+};
+
/**
* rdtgroup_pseudo_lock_create - Create a pseudo-locked region
* @rdtgrp: resource group to which pseudo-lock region belongs
goto out_region;
}
+ if (!IS_ERR_OR_NULL(debugfs_resctrl)) {
+ plr->debugfs_dir = debugfs_create_dir(rdtgrp->kn->name,
+ debugfs_resctrl);
+ if (!IS_ERR_OR_NULL(plr->debugfs_dir))
+ debugfs_create_file("pseudo_lock_measure", 0200,
+ plr->debugfs_dir, rdtgrp,
+ &pseudo_measure_fops);
+ }
+
rdtgrp->mode = RDT_MODE_PSEUDO_LOCKED;
closid_free(rdtgrp->closid);
ret = 0;
*/
void rdtgroup_pseudo_lock_remove(struct rdtgroup *rdtgrp)
{
- if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP)
+ if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
/*
* Default group cannot be a pseudo-locked region so we can
* free closid here.
*/
closid_free(rdtgrp->closid);
+ goto free;
+ }
+
+ debugfs_remove_recursive(rdtgrp->plr->debugfs_dir);
+free:
pseudo_lock_free(rdtgrp);
}
projects / openwrt / staging / blogic.git / commitdiff