linux - Oprofile 警告 "could not check that the binary file"

Question

我们使用 Oprofile 对内核模块进行分析，并且在 opreport 中有如下警告

warning: could not check that the binary file /lib/modules/2.6.32-191.el6.x86_64/kernel/fs/ext4/ext4.ko has not been modified since the profile was taken. Results may be inaccurate.
1591    samples % symbol name
1592    1622 9.8381 ext4_iget
1593    1591 9.6500 ext4_find_entry
1594    1231 7.4665 __ext4_get_inode_loc
1595    783 4.7492 ext4_ext_get_blocks
1596    752 4.5612 ext4_check_dir_entry
1597    644 3.9061 ext4_mark_iloc_dirty
1598    583 3.5361 ext4_get_blocks
1599    583 3.5361 ext4_xattr_get

谁能解释一下这个警告是什么，它会影响 oprofile 输出的准确性吗？无论如何都可以避免这个警告吗？

如有任何建议，我们将不胜感激。非常感谢!

添加更多信息: 在 daemon/opd_mangling.c

if (!sf->kernel)
    binary = find_cookie(sf->cookie);
else
    binary = sf->kernel->name;
...
fill_header(odb_get_data(file), counter,
        sf->anon ? sf->anon->start : 0, last_start,
        !!sf->kernel, last ? !!last->kernel : 0,
        spu_profile, sf->embedded_offset,
        binary ? op_get_mtime(binary) : 0);

对于内核模块文件，sf->kernel->name是内核模块名，所以fill header总是用0填充mtime并生成不需要的警告

Answer 1

此失败表示相关文件的 stat 失败。执行 strace -e stat 以查看具体的故障模式。

time_t op_get_mtime(char const * file)
{
    struct stat st;

    if (stat(file, &st))
        return 0;

    return st.st_mtime;
}
...
    if (!header.mtime) {
        // FIXME: header.mtime for JIT sample files is 0. The problem could be that
        //        in opd_mangling.c:opd_open_sample_file() the call of fill_header()
        //        think that the JIT sample file is not a binary file.
        if (is_jit_sample(file)) {
            cverb << vbfd << "warning: could not check that the binary file "
                  << file << " has not been modified since "
                  "the profile was taken. Results may be inaccurate.\n";

does it impact the accuracy of the oprofile output and is there anyway to avoid this warning?

是的，它会影响输出，因为它没有机会警告您“二进制文件的最后修改时间与样本文件的最后修改时间不匹配...”。只要您确定测量的内容与现在安装的二进制文件相匹配，您看到的警告是无害的。