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Date: Wed, 05 Dec 2018 18:48:06 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Namhyung Kim <namhyung@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Tom Zanussi <zanussi@...nel.org>,
Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: [for-next][PATCH 17/30] tracing: Add tracefs file buffer_percentage
From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Add a "buffer_percentage" file, that allows users to specify how much of the
buffer (percentage of pages) need to be filled before waking up a task
blocked on a per cpu trace_pipe_raw file.
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
kernel/trace/ring_buffer.c | 39 ++++++++++++++++-----------
kernel/trace/trace.c | 54 +++++++++++++++++++++++++++++++++++++-
kernel/trace/trace.h | 1 +
3 files changed, 77 insertions(+), 17 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9edb628603ab..5434c16f2192 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -489,6 +489,7 @@ struct ring_buffer_per_cpu {
local_t commits;
local_t pages_touched;
local_t pages_read;
+ long last_pages_touch;
size_t shortest_full;
unsigned long read;
unsigned long read_bytes;
@@ -2632,7 +2633,9 @@ static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
static __always_inline void
rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
{
- bool pagebusy;
+ size_t nr_pages;
+ size_t dirty;
+ size_t full;
if (buffer->irq_work.waiters_pending) {
buffer->irq_work.waiters_pending = false;
@@ -2646,24 +2649,27 @@ rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
irq_work_queue(&cpu_buffer->irq_work.work);
}
- pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
+ if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
+ return;
- if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) {
- size_t nr_pages;
- size_t dirty;
- size_t full;
+ if (cpu_buffer->reader_page == cpu_buffer->commit_page)
+ return;
- full = cpu_buffer->shortest_full;
- nr_pages = cpu_buffer->nr_pages;
- dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
- if (full && nr_pages && (dirty * 100) <= full * nr_pages)
- return;
+ if (!cpu_buffer->irq_work.full_waiters_pending)
+ return;
- cpu_buffer->irq_work.wakeup_full = true;
- cpu_buffer->irq_work.full_waiters_pending = false;
- /* irq_work_queue() supplies it's own memory barriers */
- irq_work_queue(&cpu_buffer->irq_work.work);
- }
+ cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
+
+ full = cpu_buffer->shortest_full;
+ nr_pages = cpu_buffer->nr_pages;
+ dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
+ if (full && nr_pages && (dirty * 100) <= full * nr_pages)
+ return;
+
+ cpu_buffer->irq_work.wakeup_full = true;
+ cpu_buffer->irq_work.full_waiters_pending = false;
+ /* irq_work_queue() supplies it's own memory barriers */
+ irq_work_queue(&cpu_buffer->irq_work.work);
}
/*
@@ -4394,6 +4400,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
local_set(&cpu_buffer->commits, 0);
local_set(&cpu_buffer->pages_touched, 0);
local_set(&cpu_buffer->pages_read, 0);
+ cpu_buffer->last_pages_touch = 0;
cpu_buffer->shortest_full = 0;
cpu_buffer->read = 0;
cpu_buffer->read_bytes = 0;
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 48d5eb22ff33..d382fd1aa4a6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6948,7 +6948,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK))
goto out;
- ret = wait_on_pipe(iter, 1);
+ ret = wait_on_pipe(iter, iter->tr->buffer_percent);
if (ret)
goto out;
@@ -7662,6 +7662,53 @@ static const struct file_operations rb_simple_fops = {
.llseek = default_llseek,
};
+static ssize_t
+buffer_percent_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct trace_array *tr = filp->private_data;
+ char buf[64];
+ int r;
+
+ r = tr->buffer_percent;
+ r = sprintf(buf, "%d\n", r);
+
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+buffer_percent_write(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct trace_array *tr = filp->private_data;
+ unsigned long val;
+ int ret;
+
+ ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
+ if (ret)
+ return ret;
+
+ if (val > 100)
+ return -EINVAL;
+
+ if (!val)
+ val = 1;
+
+ tr->buffer_percent = val;
+
+ (*ppos)++;
+
+ return cnt;
+}
+
+static const struct file_operations buffer_percent_fops = {
+ .open = tracing_open_generic_tr,
+ .read = buffer_percent_read,
+ .write = buffer_percent_write,
+ .release = tracing_release_generic_tr,
+ .llseek = default_llseek,
+};
+
struct dentry *trace_instance_dir;
static void
@@ -7970,6 +8017,11 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
trace_create_file("timestamp_mode", 0444, d_tracer, tr,
&trace_time_stamp_mode_fops);
+ tr->buffer_percent = 1;
+
+ trace_create_file("buffer_percent", 0444, d_tracer,
+ tr, &buffer_percent_fops);
+
create_trace_options_dir(tr);
#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ab16eca76e59..08900828d282 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -247,6 +247,7 @@ struct trace_array {
int clock_id;
int nr_topts;
bool clear_trace;
+ int buffer_percent;
struct tracer *current_trace;
unsigned int trace_flags;
unsigned char trace_flags_index[TRACE_FLAGS_MAX_SIZE];
--
2.19.1
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