[2/2] dmabuf/tracing: Add dma-buf trace events
diff mbox series

Message ID 20200803144719.3184138-3-kaleshsingh@google.com
State New
Headers show
Series
  • Per process tracking of dma buffers
Related show

Commit Message

Kalesh Singh Aug. 3, 2020, 2:47 p.m. UTC
Being able to analyze the per process usage of shared
dma buffers prodives useful insights in situations where
the system is experiencing high memory pressure. This would
allow us to see exactly which processes are holding references
to the shared buffer.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 drivers/dma-buf/dma-buf.c      | 29 +++++++++++++
 include/trace/events/dma_buf.h | 77 ++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 include/trace/events/dma_buf.h

Comments

Matthew Wilcox Aug. 3, 2020, 3:41 p.m. UTC | #1
On Mon, Aug 03, 2020 at 02:47:19PM +0000, Kalesh Singh wrote:
> +static void dma_buf_fd_install(int fd, struct file *filp)
> +{
> +	trace_dma_buf_fd_ref_inc(current, filp);
> +}

You're adding a new file_operation in order to just add a new tracepoint?
NACK.
Suren Baghdasaryan Aug. 3, 2020, 4 p.m. UTC | #2
On Mon, Aug 3, 2020 at 8:41 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Aug 03, 2020 at 02:47:19PM +0000, Kalesh Singh wrote:
> > +static void dma_buf_fd_install(int fd, struct file *filp)
> > +{
> > +     trace_dma_buf_fd_ref_inc(current, filp);
> > +}
>
> You're adding a new file_operation in order to just add a new tracepoint?
> NACK.

Hi Matthew,
The plan is to attach a BPF to this tracepoint in order to track
dma-buf users. If you feel this is an overkill, what would you suggest
as an alternative?
Kalesh Singh Aug. 3, 2020, 4:33 p.m. UTC | #3
On Mon, Aug 03, 2020 at 11:32:39AM -0400, Steven Rostedt wrote:
> On Mon,  3 Aug 2020 14:47:19 +0000
> Kalesh Singh <kaleshsingh@google.com> wrote:
> 
> > +DECLARE_EVENT_CLASS(dma_buf_ref_template,
> > +
> > +	TP_PROTO(struct task_struct *task, struct file *filp),
> > +
> > +	TP_ARGS(task,  filp),
> > +
> > +	TP_STRUCT__entry(
> > +		__field(u32, tgid)
> > +		__field(u32, pid)
> 
> I only see "current" passed in as "task". Why are you recording the pid
> and tgid as these are available by the tracing infrastructure.
> 
> At least the pid is saved at every event. You can see the tgid when
> enabling the "record_tgid".
> 
>  # trace-cmd start -e all -O record_tgid
>  # trace-cmd show
> 
> # tracer: nop
> #
> # entries-in-buffer/entries-written: 39750/39750   #P:8
> #
> #                                      _-----=> irqs-off
> #                                     / _----=> need-resched
> #                                    | / _---=> hardirq/softirq
> #                                    || / _--=> preempt-depth
> #                                    ||| /     delay
> #           TASK-PID    TGID   CPU#  ||||    TIMESTAMP  FUNCTION
> #              | |        |      |   ||||       |         |
>        trace-cmd-28284 (28284) [005] .... 240338.934671: sys_exit: NR 1 = 1
>      kworker/3:2-27891 (27891) [003] d... 240338.934671: timer_start: timer=00000000d643debd function=delayed_work_timer_fn expires=4535008893 [timeout=1981] cpu=3 idx=186 flags=I
>        trace-cmd-28284 (28284) [005] .... 240338.934672: sys_write -> 0x1
>      kworker/3:2-27891 (27891) [003] .... 240338.934672: workqueue_execute_end: work struct 000000008fddd403: function psi_avgs_work
>      kworker/3:2-27891 (27891) [003] .... 240338.934673: workqueue_execute_start: work struct 00000000111c941e: function dbs_work_handler
>      kworker/3:2-27891 (27891) [003] .... 240338.934673: workqueue_execute_end: work struct 00000000111c941e: function dbs_work_handler
>      kworker/3:2-27891 (27891) [003] d... 240338.934673: rcu_utilization: Start context switch
>      kworker/3:2-27891 (27891) [003] d... 240338.934673: rcu_utilization: End context switch
> 
> -- Steve
> 
Thanks for the comments Steve. I'll remove the task arg.

> > +		__field(u64, size)
> > +		__field(s64, count)
> > +		__string(exp_name, dma_buffer(filp)->exp_name)
> > +		__string(name, dma_buffer(filp)->name ? dma_buffer(filp)->name : UNKNOWN)
> > +		__field(u64, i_ino)
> > +	),
> > +
> > +	TP_fast_assign(
> > +		__entry->tgid = task->tgid;
> > +		__entry->pid = task->pid;
> > +		__entry->size = dma_buffer(filp)->size;
> > +		__entry->count = file_count(filp);
> > +		__assign_str(exp_name, dma_buffer(filp)->exp_name);
> > +		__assign_str(name, dma_buffer(filp)->name ? dma_buffer(filp)->name : UNKNOWN);
> > +		__entry->i_ino = filp->f_inode->i_ino;
> > +	),
> > +

Patch
diff mbox series

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 1ca609f66fdf..1729191ac9ca 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -29,6 +29,9 @@ 
 #include <uapi/linux/dma-buf.h>
 #include <uapi/linux/magic.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/dma_buf.h>
+
 static inline int is_dma_buf_file(struct file *);
 
 struct dma_buf_list {
@@ -110,6 +113,15 @@  static struct file_system_type dma_buf_fs_type = {
 	.kill_sb = kill_anon_super,
 };
 
+static void dma_buf_vma_close(struct vm_area_struct *area)
+{
+	trace_dma_buf_map_ref_dec(current, area->vm_file);
+}
+
+static const struct vm_operations_struct dma_buf_vm_ops = {
+	.close = dma_buf_vma_close,
+};
+
 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
 {
 	struct dma_buf *dmabuf;
@@ -128,6 +140,9 @@  static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
 	    dmabuf->size >> PAGE_SHIFT)
 		return -EINVAL;
 
+	trace_dma_buf_map_ref_inc(current, file);
+	vma->vm_ops = &dma_buf_vm_ops;
+
 	return dmabuf->ops->mmap(dmabuf, vma);
 }
 
@@ -410,6 +425,17 @@  static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
 	spin_unlock(&dmabuf->name_lock);
 }
 
+static int dma_buf_flush(struct file *filp, fl_owner_t id)
+{
+	trace_dma_buf_fd_ref_dec(current, filp);
+	return 0;
+}
+
+static void dma_buf_fd_install(int fd, struct file *filp)
+{
+	trace_dma_buf_fd_ref_inc(current, filp);
+}
+
 static const struct file_operations dma_buf_fops = {
 	.mmap		= dma_buf_mmap_internal,
 	.llseek		= dma_buf_llseek,
@@ -417,6 +443,8 @@  static const struct file_operations dma_buf_fops = {
 	.unlocked_ioctl	= dma_buf_ioctl,
 	.compat_ioctl	= compat_ptr_ioctl,
 	.show_fdinfo	= dma_buf_show_fdinfo,
+	.fd_install	= dma_buf_fd_install,
+	.flush		= dma_buf_flush,
 };
 
 /*
@@ -1177,6 +1205,7 @@  int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
 		if (oldfile)
 			fput(oldfile);
 	}
+
 	return ret;
 
 }
diff --git a/include/trace/events/dma_buf.h b/include/trace/events/dma_buf.h
new file mode 100644
index 000000000000..05af336cd849
--- /dev/null
+++ b/include/trace/events/dma_buf.h
@@ -0,0 +1,77 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM dma_buf
+
+#if !defined(_TRACE_DMA_BUF_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_DMA_BUF_H
+
+#include <linux/dma-buf.h>
+#include <linux/tracepoint.h>
+#include <linux/types.h>
+
+#define UNKNOWN "<unknown>"
+
+#ifdef CREATE_TRACE_POINTS
+static inline struct dma_buf *dma_buffer(struct file *filp)
+{
+	return filp->private_data;
+}
+#endif
+
+DECLARE_EVENT_CLASS(dma_buf_ref_template,
+
+	TP_PROTO(struct task_struct *task, struct file *filp),
+
+	TP_ARGS(task,  filp),
+
+	TP_STRUCT__entry(
+		__field(u32, tgid)
+		__field(u32, pid)
+		__field(u64, size)
+		__field(s64, count)
+		__string(exp_name, dma_buffer(filp)->exp_name)
+		__string(name, dma_buffer(filp)->name ? dma_buffer(filp)->name : UNKNOWN)
+		__field(u64, i_ino)
+	),
+
+	TP_fast_assign(
+		__entry->tgid = task->tgid;
+		__entry->pid = task->pid;
+		__entry->size = dma_buffer(filp)->size;
+		__entry->count = file_count(filp);
+		__assign_str(exp_name, dma_buffer(filp)->exp_name);
+		__assign_str(name, dma_buffer(filp)->name ? dma_buffer(filp)->name : UNKNOWN);
+		__entry->i_ino = filp->f_inode->i_ino;
+	),
+
+	TP_printk("tgid=%u pid=%u size=%llu count=%lld exp_name=%s name=%s i_ino=%llu",
+		__entry->tgid,
+		__entry->pid,
+		__entry->size,
+		__entry->count,
+		__get_str(exp_name),
+		__get_str(name),
+		__entry->i_ino
+	)
+);
+
+DEFINE_EVENT(dma_buf_ref_template, dma_buf_fd_ref_inc,
+	TP_PROTO(struct task_struct *task, struct file *filp),
+	TP_ARGS(task,  filp));
+
+DEFINE_EVENT(dma_buf_ref_template, dma_buf_fd_ref_dec,
+	TP_PROTO(struct task_struct *task, struct file *filp),
+	TP_ARGS(task,  filp));
+
+DEFINE_EVENT(dma_buf_ref_template, dma_buf_map_ref_inc,
+	TP_PROTO(struct task_struct *task, struct file *filp),
+	TP_ARGS(task,  filp));
+
+DEFINE_EVENT(dma_buf_ref_template, dma_buf_map_ref_dec,
+	TP_PROTO(struct task_struct *task, struct file *filp),
+	TP_ARGS(task,  filp));
+
+#endif /* _TRACE_DMA_BUF_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>