Re: [Linaro-mm-sig] [PATCH 2/2] dmabuf/tracing: Add dma-buf trace events

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

• __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;
  

• ),