From 7b732a75047738e4f85438ed2f9cd34bf5f2a19a Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 23 Mar 2009 18:22:10 +0100 Subject: [PATCH] perf_counter: new output ABI - part 1 Impact: Rework the perfcounter output ABI use sys_read() only for instant data and provide mmap() output for all async overflow data. The first mmap() determines the size of the output buffer. The mmap() size must be a PAGE_SIZE multiple of 1+pages, where pages must be a power of 2 or 0. Further mmap()s of the same fd must have the same size. Once all maps are gone, you can again mmap() with a new size. In case of 0 extra pages there is no data output and the first page only contains meta data. When there are data pages, a poll() event will be generated for each full page of data. Furthermore, the output is circular. This means that although 1 page is a valid configuration, its useless, since we'll start overwriting it the instant we report a full page. Future work will focus on the output format (currently maintained) where we'll likey want each entry denoted by a header which includes a type and length. Further future work will allow to splice() the fd, also containing the async overflow data -- splice() would be mutually exclusive with mmap() of the data. Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Orig-LKML-Reference: <20090323172417.470536358@chello.nl> Signed-off-by: Ingo Molnar --- arch/powerpc/kernel/perf_counter.c | 9 +- include/linux/perf_counter.h | 36 +-- kernel/perf_counter.c | 464 +++++++++++++++-------------- 3 files changed, 263 insertions(+), 246 deletions(-) diff --git a/arch/powerpc/kernel/perf_counter.c b/arch/powerpc/kernel/perf_counter.c index e4349281b07d..d48596ab6557 100644 --- a/arch/powerpc/kernel/perf_counter.c +++ b/arch/powerpc/kernel/perf_counter.c @@ -417,8 +417,7 @@ void hw_perf_restore(u64 disable) atomic64_set(&counter->hw.prev_count, val); counter->hw.idx = hwc_index[i] + 1; write_pmc(counter->hw.idx, val); - if (counter->user_page) - perf_counter_update_userpage(counter); + perf_counter_update_userpage(counter); } mb(); cpuhw->mmcr[0] |= MMCR0_PMXE | MMCR0_FCECE; @@ -574,8 +573,7 @@ static void power_perf_disable(struct perf_counter *counter) ppmu->disable_pmc(counter->hw.idx - 1, cpuhw->mmcr); write_pmc(counter->hw.idx, 0); counter->hw.idx = 0; - if (counter->user_page) - perf_counter_update_userpage(counter); + perf_counter_update_userpage(counter); break; } } @@ -702,8 +700,7 @@ static void record_and_restart(struct perf_counter *counter, long val, write_pmc(counter->hw.idx, val); atomic64_set(&counter->hw.prev_count, val); atomic64_set(&counter->hw.period_left, left); - if (counter->user_page) - perf_counter_update_userpage(counter); + perf_counter_update_userpage(counter); /* * Finally record data if requested. diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index 40b324e91bf6..2b5e66d5ebdf 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -152,6 +152,8 @@ struct perf_counter_mmap_page { __u32 lock; /* seqlock for synchronization */ __u32 index; /* hardware counter identifier */ __s64 offset; /* add to hardware counter value */ + + __u32 data_head; /* head in the data section */ }; #ifdef __KERNEL__ @@ -218,21 +220,6 @@ struct hw_perf_counter { #endif }; -/* - * Hardcoded buffer length limit for now, for IRQ-fed events: - */ -#define PERF_DATA_BUFLEN 2048 - -/** - * struct perf_data - performance counter IRQ data sampling ... - */ -struct perf_data { - int len; - int rd_idx; - int overrun; - u8 data[PERF_DATA_BUFLEN]; -}; - struct perf_counter; /** @@ -256,6 +243,14 @@ enum perf_counter_active_state { struct file; +struct perf_mmap_data { + struct rcu_head rcu_head; + int nr_pages; + atomic_t head; + struct perf_counter_mmap_page *user_page; + void *data_pages[0]; +}; + /** * struct perf_counter - performance counter kernel representation: */ @@ -289,16 +284,15 @@ struct perf_counter { int oncpu; int cpu; - /* pointer to page shared with userspace via mmap */ - unsigned long user_page; + /* mmap bits */ + struct mutex mmap_mutex; + atomic_t mmap_count; + struct perf_mmap_data *data; - /* read() / irq related data */ + /* poll related */ wait_queue_head_t waitq; /* optional: for NMIs */ int wakeup_pending; - struct perf_data *irqdata; - struct perf_data *usrdata; - struct perf_data data[2]; void (*destroy)(struct perf_counter *); struct rcu_head rcu_head; diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index d9cfd902140e..0dfe91094fd1 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -4,7 +4,8 @@ * Copyright(C) 2008 Thomas Gleixner * Copyright(C) 2008 Red Hat, Inc., Ingo Molnar * - * For licencing details see kernel-base/COPYING + * + * For licensing details see kernel-base/COPYING */ #include @@ -1022,66 +1023,6 @@ static u64 perf_counter_read(struct perf_counter *counter) return atomic64_read(&counter->count); } -/* - * Cross CPU call to switch performance data pointers - */ -static void __perf_switch_irq_data(void *info) -{ - struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context); - struct perf_counter *counter = info; - struct perf_counter_context *ctx = counter->ctx; - struct perf_data *oldirqdata = counter->irqdata; - - /* - * If this is a task context, we need to check whether it is - * the current task context of this cpu. If not it has been - * scheduled out before the smp call arrived. - */ - if (ctx->task) { - if (cpuctx->task_ctx != ctx) - return; - spin_lock(&ctx->lock); - } - - /* Change the pointer NMI safe */ - atomic_long_set((atomic_long_t *)&counter->irqdata, - (unsigned long) counter->usrdata); - counter->usrdata = oldirqdata; - - if (ctx->task) - spin_unlock(&ctx->lock); -} - -static struct perf_data *perf_switch_irq_data(struct perf_counter *counter) -{ - struct perf_counter_context *ctx = counter->ctx; - struct perf_data *oldirqdata = counter->irqdata; - struct task_struct *task = ctx->task; - - if (!task) { - smp_call_function_single(counter->cpu, - __perf_switch_irq_data, - counter, 1); - return counter->usrdata; - } - -retry: - spin_lock_irq(&ctx->lock); - if (counter->state != PERF_COUNTER_STATE_ACTIVE) { - counter->irqdata = counter->usrdata; - counter->usrdata = oldirqdata; - spin_unlock_irq(&ctx->lock); - return oldirqdata; - } - spin_unlock_irq(&ctx->lock); - task_oncpu_function_call(task, __perf_switch_irq_data, counter); - /* Might have failed, because task was scheduled out */ - if (counter->irqdata == oldirqdata) - goto retry; - - return counter->usrdata; -} - static void put_context(struct perf_counter_context *ctx) { if (ctx->task) @@ -1177,7 +1118,6 @@ static int perf_release(struct inode *inode, struct file *file) mutex_unlock(&counter->mutex); mutex_unlock(&ctx->mutex); - free_page(counter->user_page); free_counter(counter); put_context(ctx); @@ -1192,7 +1132,7 @@ perf_read_hw(struct perf_counter *counter, char __user *buf, size_t count) { u64 cntval; - if (count != sizeof(cntval)) + if (count < sizeof(cntval)) return -EINVAL; /* @@ -1210,122 +1150,21 @@ perf_read_hw(struct perf_counter *counter, char __user *buf, size_t count) return put_user(cntval, (u64 __user *) buf) ? -EFAULT : sizeof(cntval); } -static ssize_t -perf_copy_usrdata(struct perf_data *usrdata, char __user *buf, size_t count) -{ - if (!usrdata->len) - return 0; - - count = min(count, (size_t)usrdata->len); - if (copy_to_user(buf, usrdata->data + usrdata->rd_idx, count)) - return -EFAULT; - - /* Adjust the counters */ - usrdata->len -= count; - if (!usrdata->len) - usrdata->rd_idx = 0; - else - usrdata->rd_idx += count; - - return count; -} - -static ssize_t -perf_read_irq_data(struct perf_counter *counter, - char __user *buf, - size_t count, - int nonblocking) -{ - struct perf_data *irqdata, *usrdata; - DECLARE_WAITQUEUE(wait, current); - ssize_t res, res2; - - irqdata = counter->irqdata; - usrdata = counter->usrdata; - - if (usrdata->len + irqdata->len >= count) - goto read_pending; - - if (nonblocking) - return -EAGAIN; - - spin_lock_irq(&counter->waitq.lock); - __add_wait_queue(&counter->waitq, &wait); - for (;;) { - set_current_state(TASK_INTERRUPTIBLE); - if (usrdata->len + irqdata->len >= count) - break; - - if (signal_pending(current)) - break; - - if (counter->state == PERF_COUNTER_STATE_ERROR) - break; - - spin_unlock_irq(&counter->waitq.lock); - schedule(); - spin_lock_irq(&counter->waitq.lock); - } - __remove_wait_queue(&counter->waitq, &wait); - __set_current_state(TASK_RUNNING); - spin_unlock_irq(&counter->waitq.lock); - - if (usrdata->len + irqdata->len < count && - counter->state != PERF_COUNTER_STATE_ERROR) - return -ERESTARTSYS; -read_pending: - mutex_lock(&counter->mutex); - - /* Drain pending data first: */ - res = perf_copy_usrdata(usrdata, buf, count); - if (res < 0 || res == count) - goto out; - - /* Switch irq buffer: */ - usrdata = perf_switch_irq_data(counter); - res2 = perf_copy_usrdata(usrdata, buf + res, count - res); - if (res2 < 0) { - if (!res) - res = -EFAULT; - } else { - res += res2; - } -out: - mutex_unlock(&counter->mutex); - - return res; -} - static ssize_t perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct perf_counter *counter = file->private_data; - switch (counter->hw_event.record_type) { - case PERF_RECORD_SIMPLE: - return perf_read_hw(counter, buf, count); - - case PERF_RECORD_IRQ: - case PERF_RECORD_GROUP: - return perf_read_irq_data(counter, buf, count, - file->f_flags & O_NONBLOCK); - } - return -EINVAL; + return perf_read_hw(counter, buf, count); } static unsigned int perf_poll(struct file *file, poll_table *wait) { struct perf_counter *counter = file->private_data; - unsigned int events = 0; - unsigned long flags; + unsigned int events = POLLIN; poll_wait(file, &counter->waitq, wait); - spin_lock_irqsave(&counter->waitq.lock, flags); - if (counter->usrdata->len || counter->irqdata->len) - events |= POLLIN; - spin_unlock_irqrestore(&counter->waitq.lock, flags); - return events; } @@ -1347,78 +1186,207 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg) return err; } -void perf_counter_update_userpage(struct perf_counter *counter) +static void __perf_counter_update_userpage(struct perf_counter *counter, + struct perf_mmap_data *data) { - struct perf_counter_mmap_page *userpg; - - if (!counter->user_page) - return; - userpg = (struct perf_counter_mmap_page *) counter->user_page; + struct perf_counter_mmap_page *userpg = data->user_page; + /* + * Disable preemption so as to not let the corresponding user-space + * spin too long if we get preempted. + */ + preempt_disable(); ++userpg->lock; smp_wmb(); userpg->index = counter->hw.idx; userpg->offset = atomic64_read(&counter->count); if (counter->state == PERF_COUNTER_STATE_ACTIVE) userpg->offset -= atomic64_read(&counter->hw.prev_count); + + userpg->data_head = atomic_read(&data->head); smp_wmb(); ++userpg->lock; + preempt_enable(); +} + +void perf_counter_update_userpage(struct perf_counter *counter) +{ + struct perf_mmap_data *data; + + rcu_read_lock(); + data = rcu_dereference(counter->data); + if (data) + __perf_counter_update_userpage(counter, data); + rcu_read_unlock(); } static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) { struct perf_counter *counter = vma->vm_file->private_data; + struct perf_mmap_data *data; + int ret = VM_FAULT_SIGBUS; - if (!counter->user_page) - return VM_FAULT_SIGBUS; + rcu_read_lock(); + data = rcu_dereference(counter->data); + if (!data) + goto unlock; + + if (vmf->pgoff == 0) { + vmf->page = virt_to_page(data->user_page); + } else { + int nr = vmf->pgoff - 1; - vmf->page = virt_to_page(counter->user_page); + if ((unsigned)nr > data->nr_pages) + goto unlock; + + vmf->page = virt_to_page(data->data_pages[nr]); + } get_page(vmf->page); + ret = 0; +unlock: + rcu_read_unlock(); + + return ret; +} + +static int perf_mmap_data_alloc(struct perf_counter *counter, int nr_pages) +{ + struct perf_mmap_data *data; + unsigned long size; + int i; + + WARN_ON(atomic_read(&counter->mmap_count)); + + size = sizeof(struct perf_mmap_data); + size += nr_pages * sizeof(void *); + + data = kzalloc(size, GFP_KERNEL); + if (!data) + goto fail; + + data->user_page = (void *)get_zeroed_page(GFP_KERNEL); + if (!data->user_page) + goto fail_user_page; + + for (i = 0; i < nr_pages; i++) { + data->data_pages[i] = (void *)get_zeroed_page(GFP_KERNEL); + if (!data->data_pages[i]) + goto fail_data_pages; + } + + data->nr_pages = nr_pages; + + rcu_assign_pointer(counter->data, data); + return 0; + +fail_data_pages: + for (i--; i >= 0; i--) + free_page((unsigned long)data->data_pages[i]); + + free_page((unsigned long)data->user_page); + +fail_user_page: + kfree(data); + +fail: + return -ENOMEM; +} + +static void __perf_mmap_data_free(struct rcu_head *rcu_head) +{ + struct perf_mmap_data *data = container_of(rcu_head, + struct perf_mmap_data, rcu_head); + int i; + + free_page((unsigned long)data->user_page); + for (i = 0; i < data->nr_pages; i++) + free_page((unsigned long)data->data_pages[i]); + kfree(data); +} + +static void perf_mmap_data_free(struct perf_counter *counter) +{ + struct perf_mmap_data *data = counter->data; + + WARN_ON(atomic_read(&counter->mmap_count)); + + rcu_assign_pointer(counter->data, NULL); + call_rcu(&data->rcu_head, __perf_mmap_data_free); +} + +static void perf_mmap_open(struct vm_area_struct *vma) +{ + struct perf_counter *counter = vma->vm_file->private_data; + + atomic_inc(&counter->mmap_count); +} + +static void perf_mmap_close(struct vm_area_struct *vma) +{ + struct perf_counter *counter = vma->vm_file->private_data; + + if (atomic_dec_and_mutex_lock(&counter->mmap_count, + &counter->mmap_mutex)) { + perf_mmap_data_free(counter); + mutex_unlock(&counter->mmap_mutex); + } } static struct vm_operations_struct perf_mmap_vmops = { + .open = perf_mmap_open, + .close = perf_mmap_close, .fault = perf_mmap_fault, }; static int perf_mmap(struct file *file, struct vm_area_struct *vma) { struct perf_counter *counter = file->private_data; - unsigned long userpg; + unsigned long vma_size; + unsigned long nr_pages; + unsigned long locked, lock_limit; + int ret = 0; if (!(vma->vm_flags & VM_SHARED) || (vma->vm_flags & VM_WRITE)) return -EINVAL; - if (vma->vm_end - vma->vm_start != PAGE_SIZE) + + vma_size = vma->vm_end - vma->vm_start; + nr_pages = (vma_size / PAGE_SIZE) - 1; + + if (nr_pages == 0 || !is_power_of_2(nr_pages)) return -EINVAL; - /* - * For now, restrict to the case of a hardware counter - * on the current task. - */ - if (is_software_counter(counter) || counter->task != current) + if (vma_size != PAGE_SIZE * (1 + nr_pages)) return -EINVAL; - userpg = counter->user_page; - if (!userpg) { - userpg = get_zeroed_page(GFP_KERNEL); - mutex_lock(&counter->mutex); - if (counter->user_page) { - free_page(userpg); - userpg = counter->user_page; - } else { - counter->user_page = userpg; - } - mutex_unlock(&counter->mutex); - if (!userpg) - return -ENOMEM; - } + if (vma->vm_pgoff != 0) + return -EINVAL; + + locked = vma_size >> PAGE_SHIFT; + locked += vma->vm_mm->locked_vm; - perf_counter_update_userpage(counter); + lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; + lock_limit >>= PAGE_SHIFT; + + if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) + return -EPERM; + + mutex_lock(&counter->mmap_mutex); + if (atomic_inc_not_zero(&counter->mmap_count)) + goto out; + + WARN_ON(counter->data); + ret = perf_mmap_data_alloc(counter, nr_pages); + if (!ret) + atomic_set(&counter->mmap_count, 1); +out: + mutex_unlock(&counter->mmap_mutex); vma->vm_flags &= ~VM_MAYWRITE; vma->vm_flags |= VM_RESERVED; vma->vm_ops = &perf_mmap_vmops; - return 0; + + return ret; } static const struct file_operations perf_fops = { @@ -1434,30 +1402,94 @@ static const struct file_operations perf_fops = { * Output */ -static void perf_counter_store_irq(struct perf_counter *counter, u64 data) +static int perf_output_write(struct perf_counter *counter, int nmi, + void *buf, ssize_t size) { - struct perf_data *irqdata = counter->irqdata; + struct perf_mmap_data *data; + unsigned int offset, head, nr; + unsigned int len; + int ret, wakeup; - if (irqdata->len > PERF_DATA_BUFLEN - sizeof(u64)) { - irqdata->overrun++; - } else { - u64 *p = (u64 *) &irqdata->data[irqdata->len]; + rcu_read_lock(); + ret = -ENOSPC; + data = rcu_dereference(counter->data); + if (!data) + goto out; + + if (!data->nr_pages) + goto out; + + ret = -EINVAL; + if (size > PAGE_SIZE) + goto out; + + do { + offset = head = atomic_read(&data->head); + head += sizeof(u64); + } while (atomic_cmpxchg(&data->head, offset, head) != offset); + + wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT); - *p = data; - irqdata->len += sizeof(u64); + nr = (offset >> PAGE_SHIFT) & (data->nr_pages - 1); + offset &= PAGE_SIZE - 1; + + len = min_t(unsigned int, PAGE_SIZE - offset, size); + memcpy(data->data_pages[nr] + offset, buf, len); + size -= len; + + if (size) { + nr = (nr + 1) & (data->nr_pages - 1); + memcpy(data->data_pages[nr], buf + len, size); + } + + /* + * generate a poll() wakeup for every page boundary crossed + */ + if (wakeup) { + __perf_counter_update_userpage(counter, data); + if (nmi) { + counter->wakeup_pending = 1; + set_perf_counter_pending(); + } else + wake_up(&counter->waitq); } + ret = 0; +out: + rcu_read_unlock(); + + return ret; } -static void perf_counter_handle_group(struct perf_counter *counter) +static void perf_output_simple(struct perf_counter *counter, + int nmi, struct pt_regs *regs) +{ + u64 entry; + + entry = instruction_pointer(regs); + + perf_output_write(counter, nmi, &entry, sizeof(entry)); +} + +struct group_entry { + u64 event; + u64 counter; +}; + +static void perf_output_group(struct perf_counter *counter, int nmi) { struct perf_counter *leader, *sub; leader = counter->group_leader; list_for_each_entry(sub, &leader->sibling_list, list_entry) { + struct group_entry entry; + if (sub != counter) sub->hw_ops->read(sub); - perf_counter_store_irq(counter, sub->hw_event.config); - perf_counter_store_irq(counter, atomic64_read(&sub->count)); + + entry.event = sub->hw_event.config; + entry.counter = atomic64_read(&sub->count); + + perf_output_write(counter, nmi, &entry, sizeof(entry)); } } @@ -1469,19 +1501,13 @@ void perf_counter_output(struct perf_counter *counter, return; case PERF_RECORD_IRQ: - perf_counter_store_irq(counter, instruction_pointer(regs)); + perf_output_simple(counter, nmi, regs); break; case PERF_RECORD_GROUP: - perf_counter_handle_group(counter); + perf_output_group(counter, nmi); break; } - - if (nmi) { - counter->wakeup_pending = 1; - set_perf_counter_pending(); - } else - wake_up(&counter->waitq); } /* @@ -1967,10 +1993,10 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event, INIT_LIST_HEAD(&counter->sibling_list); init_waitqueue_head(&counter->waitq); + mutex_init(&counter->mmap_mutex); + INIT_LIST_HEAD(&counter->child_list); - counter->irqdata = &counter->data[0]; - counter->usrdata = &counter->data[1]; counter->cpu = cpu; counter->hw_event = *hw_event; counter->wakeup_pending = 0; -- 2.20.1