[리눅스커널] tracing: 부팅 과정에서 ftrace ring-buffer 늘리기

<커널: v5.10>

 

부팅 과정에서 ftrace 로깅이 될 때 ftrace ring-buffer 사이즈가 충분해야 부팅 과정의 

메시지를 ftrace에 저장할 수 있습니다. ring-buffer 사이즈가 작으면 메시지가 overwritten됩니다. 

 

본 페이지에 소개된 패치를 적용하면 부팅 과정에서 ftracing ring-buffer 사이즈를 키울 수 있습니다.

 

commit 0deada593566918d6ac4a3e8df7bca8584fd83e1 (HEAD -> rpi-5.10.y)

Author: Austin Kim <austindh.kim@gmail.com>

Date:   Mon Sep 20 14:52:54 2021 +0900

 

    tracing: increase ftrace ring-buffer size

 

    In case ftrace ring-buffer size is small,

    ftrace message could be overwritten. As a result of this,

    the useful ftrace message can be lost.

 

    With this commit, we could increase ftrace ring-buffer size.

 

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c

old mode 100644

new mode 100755

index b09c59806..8cb872543

--- a/kernel/trace/trace.c

+++ b/kernel/trace/trace.c

@@ -6541,6 +6541,8 @@ tracing_entries_read(struct file *filp, char __user *ubuf,

        return ret;

 }

 

+#define TRACING_FTRACE_MAX_BUFFER_SIZE (4096 * 2)

+

 static ssize_t

 tracing_entries_write(struct file *filp, const char __user *ubuf,

                      size_t cnt, loff_t *ppos)

@@ -6558,6 +6560,10 @@ tracing_entries_write(struct file *filp, const char __user *ubuf,

        if (!val)

                return -EINVAL;

 

+       if( val < TRACING_FTRACE_MAX_BUFFER_SIZE ) {

+               val = TRACING_FTRACE_MAX_BUFFER_SIZE;

+       }

+

        /* value is in KB */

        val <<= 10;

        ret = tracing_resize_ring_buffer(tr, val, tracing_get_cpu(inode));