linux-kernel - Re: [PATCH] ftrace: support binary record

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Date:	Wed, 10 Dec 2008 12:49:31 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace: support binary record

Steven Rostedt wrote:
> 
> 
> On Wed, 10 Dec 2008, Lai Jiangshan wrote:
> 
>> Binary record will save memory in trace buffer, and more events
>> can be recorded in buffer.
>>
>> This patch add infrastructure for supporting binary record.
>>
>> This infrastructure records events by binary and shows events
>> by human readable text.
> 
> Hmm, interesting. But could you show an example of its use. It is quite a 
> lot of code, and looks a little complex.
consider ftrace_struct_printk() as ftrace_printk(), but the
first parameter is "struct ftrace_struct *fmt"

new file: kernel/trace/trace_struct.c : this infrastructure's code

lib/vsprintf.c : formator
other files add ftrace_struct_printk()

> 
>> And add a API ftrace_struct_printk() using this infrastructure.
>> (it's like ftrace_printk(), but it record the date by binary)
>>


example:
...
           <...>-3246  [000]  1243.166054: sys_read: sys_read by ftrace_printk, 3, asdfuuuuu
           <...>-3246  [000]  1243.166057: sys_read: sys_read by ftrace_struct_printk, 3, asdfuuuuu
           <...>-3246  [000]  1243.166490: sys_read: sys_read by ftrace_printk, 9, asdfuuuuu
           <...>-3246  [000]  1243.166491: sys_read: sys_read by ftrace_struct_printk, 9, asdfuuuuu
...
diff --git a/fs/read_write.c b/fs/read_write.c
index 969a6d9..0d9fbed 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -17,7 +17,7 @@
 #include <linux/pagemap.h>
 #include <linux/splice.h>
 #include "read_write.h"
-
+#include <linux/ftrace.h>
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 
@@ -356,12 +356,15 @@ static inline void file_pos_write(struct file *file, loff_t pos)
 	file->f_pos = pos;
 }
 
+struct ftrace_struct test = {"ixxs", "sys_read by ftrace_struct_printk, %d, %s\n"};
 asmlinkage ssize_t sys_read(unsigned int fd, char __user * buf, size_t count)
 {
 	struct file *file;
 	ssize_t ret = -EBADF;
 	int fput_needed;
 
+	ftrace_printk("sys_read by ftrace_printk, %d, %s\n", fd, "asdfuuuuu");
+	ftrace_struct_printk(&test, fd, "asdfuuuuu");
 	file = fget_light(fd, &fput_needed);
 	if (file) {
 		loff_t pos = file_pos_read(file);

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