kjournald进程占用了大量CPU,如何优化?

yj1804

主要运行的是mysql 服务器, 数据操作非常频繁, 发现运行时间比较长以后, kjournald占用了大量的CPU, 导致系统非常缓慢, 有什么优化方式么?
文件系统使用的是ext3

meiki05

调整一下文件系统的jounal模式，默认为ordered ，改成writeback会提高一些效率。

Despite writing some data more than once, ext3 is often faster (higher throughput) than ext2 because ext3's journaling optimizes hard drive head motion. You can choose from three journaling modes to optimize speed, optionally choosing to trade off some data integrity.

    * One mode, data=writeback, limits the data integrity guarantees, allowing old data to show up in files after a crash, for a potential increase in speed under some circumstances. (This mode, which is the default journaling mode for most journaling file systems, essentially provides the more limited data integrity guarantees of the ext2 file system and merely avoids the long file system check at boot time.)

    * The second mode, data=ordered (the default mode), guarantees that the data is consistent with the file system; recently-written files will never show up with garbage contents after a crash.

    * The last mode, data=journal, requires a larger journal for reasonable speed in most cases and therefore takes longer to recover in case of unclean shutdown, but is sometimes faster for certain database operations.

The default mode is recommended for general-purpose computing needs. To change the mode, add the data=something option to the mount options for that file system in the /etc/fstab file, as documented in the mount man page (man mount).

meiki05

另外可以用dumpe2fs看一下Journal size是多大，
可以想办法把Journal size的值改大一些。