ftrace: trace_entries to dynamically change trace buffer size
This patch adds /debug/tracing/trace_entries that allows users to see as well as modify the number of trace entries the buffers hold. The number of entries only increments in ENTRIES_PER_PAGE which is calculated by the size of an entry with the number of entries that can fit in a page. The user does not need to use an exact size, but the entries will be rounded to one of the increments. Trying to set the entries to 0 will return with -EINVAL. To avoid race conditions, the modification of the buffer size can only be done when tracing is completely disabled (current_tracer == none). A info message will be printed if a user tries to modify the buffer size when not set to none. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Родитель
05bd68c514
Коммит
a98a3c3fde
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@ -35,6 +35,15 @@
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unsigned long __read_mostly tracing_max_latency = (cycle_t)ULONG_MAX;
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unsigned long __read_mostly tracing_thresh;
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/* dummy trace to disable tracing */
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static struct tracer no_tracer __read_mostly =
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{
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.name = "none",
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};
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static int trace_alloc_page(void);
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static int trace_free_page(void);
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static int tracing_disabled = 1;
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long
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@ -2364,6 +2373,70 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
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return read;
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}
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static ssize_t
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tracing_entries_read(struct file *filp, char __user *ubuf,
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size_t cnt, loff_t *ppos)
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{
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struct trace_array *tr = filp->private_data;
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char buf[64];
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int r;
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r = sprintf(buf, "%lu\n", tr->entries);
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return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
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}
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static ssize_t
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tracing_entries_write(struct file *filp, const char __user *ubuf,
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size_t cnt, loff_t *ppos)
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{
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unsigned long val;
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char buf[64];
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if (cnt > 63)
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cnt = 63;
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if (copy_from_user(&buf, ubuf, cnt))
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return -EFAULT;
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buf[cnt] = 0;
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val = simple_strtoul(buf, NULL, 10);
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/* must have at least 1 entry */
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if (!val)
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return -EINVAL;
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mutex_lock(&trace_types_lock);
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if (current_trace != &no_tracer) {
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cnt = -EBUSY;
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pr_info("ftrace: set current_tracer to none"
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" before modifying buffer size\n");
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goto out;
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}
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if (val > global_trace.entries) {
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while (global_trace.entries < val) {
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if (trace_alloc_page()) {
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cnt = -ENOMEM;
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goto out;
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}
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}
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} else {
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/* include the number of entries in val (inc of page entries) */
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while (global_trace.entries > val + (ENTRIES_PER_PAGE - 1))
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trace_free_page();
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}
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filp->f_pos += cnt;
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out:
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max_tr.entries = global_trace.entries;
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mutex_unlock(&trace_types_lock);
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return cnt;
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}
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static struct file_operations tracing_max_lat_fops = {
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.open = tracing_open_generic,
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.read = tracing_max_lat_read,
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@ -2389,6 +2462,12 @@ static struct file_operations tracing_pipe_fops = {
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.release = tracing_release_pipe,
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};
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static struct file_operations tracing_entries_fops = {
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.open = tracing_open_generic,
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.read = tracing_entries_read,
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.write = tracing_entries_write,
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};
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#ifdef CONFIG_DYNAMIC_FTRACE
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static ssize_t
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@ -2500,6 +2579,12 @@ static __init void tracer_init_debugfs(void)
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pr_warning("Could not create debugfs "
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"'tracing_threash' entry\n");
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entry = debugfs_create_file("trace_entries", 0644, d_tracer,
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&global_trace, &tracing_entries_fops);
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if (!entry)
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pr_warning("Could not create debugfs "
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"'tracing_threash' entry\n");
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#ifdef CONFIG_DYNAMIC_FTRACE
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entry = debugfs_create_file("dyn_ftrace_total_info", 0444, d_tracer,
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&ftrace_update_tot_cnt,
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@ -2510,12 +2595,6 @@ static __init void tracer_init_debugfs(void)
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#endif
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}
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/* dummy trace to disable tracing */
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static struct tracer no_tracer __read_mostly =
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{
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.name = "none",
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};
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static int trace_alloc_page(void)
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{
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struct trace_array_cpu *data;
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@ -2552,7 +2631,6 @@ static int trace_alloc_page(void)
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/* Now that we successfully allocate a page per CPU, add them */
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for_each_possible_cpu(i) {
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data = global_trace.data[i];
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data->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
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page = list_entry(pages.next, struct page, lru);
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list_del_init(&page->lru);
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list_add_tail(&page->lru, &data->trace_pages);
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@ -2560,7 +2638,6 @@ static int trace_alloc_page(void)
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#ifdef CONFIG_TRACER_MAX_TRACE
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data = max_tr.data[i];
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data->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
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page = list_entry(pages.next, struct page, lru);
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list_del_init(&page->lru);
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list_add_tail(&page->lru, &data->trace_pages);
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@ -2579,6 +2656,55 @@ static int trace_alloc_page(void)
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return -ENOMEM;
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}
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static int trace_free_page(void)
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{
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struct trace_array_cpu *data;
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struct page *page;
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struct list_head *p;
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int i;
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int ret = 0;
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/* free one page from each buffer */
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for_each_possible_cpu(i) {
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data = global_trace.data[i];
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p = data->trace_pages.next;
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if (p == &data->trace_pages) {
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/* should never happen */
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WARN_ON(1);
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tracing_disabled = 1;
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ret = -1;
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break;
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}
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page = list_entry(p, struct page, lru);
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ClearPageLRU(page);
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list_del(&page->lru);
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__free_page(page);
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tracing_reset(data);
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#ifdef CONFIG_TRACER_MAX_TRACE
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data = max_tr.data[i];
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p = data->trace_pages.next;
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if (p == &data->trace_pages) {
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/* should never happen */
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WARN_ON(1);
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tracing_disabled = 1;
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ret = -1;
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break;
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}
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page = list_entry(p, struct page, lru);
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ClearPageLRU(page);
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list_del(&page->lru);
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__free_page(page);
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tracing_reset(data);
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#endif
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}
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global_trace.entries -= ENTRIES_PER_PAGE;
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return ret;
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}
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__init static int tracer_alloc_buffers(void)
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{
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struct trace_array_cpu *data;
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@ -2609,6 +2735,9 @@ __init static int tracer_alloc_buffers(void)
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/* use the LRU flag to differentiate the two buffers */
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ClearPageLRU(page);
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data->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
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max_tr.data[i]->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
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/* Only allocate if we are actually using the max trace */
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#ifdef CONFIG_TRACER_MAX_TRACE
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array = (void *)__get_free_page(GFP_KERNEL);
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