On 09/10/2013 09:02 PM, Theodore Ts'o wrote: > On Tue, Sep 10, 2013 at 02:47:33PM -0600, Andreas Dilger wrote: >> I agree that SELinux is enabled on enterprise distributions by default, >> but I'm also interested to know how much overhead this imposes. I would >> expect that writing large external xattrs for each file would have quite >> a significant performance overhead that should not be ignored. Reducing >> the mbcache overhead is good, but eliminating it entirely is better. > > I was under the impression that using a 256 byte inode (which gives a > bit over 100 bytes worth of xattr space) was plenty for SELinux. If > it turns out that SELinux's use of xattrs have gotten especially > piggy, then we may need to revisit the recommended inode size for > those systems who insist on using SELinux... even if we eliminate the > overhead associated with mbcache, the fact that files are requiring a > separate xattr is going to seriously degrade performance. > > - Ted > Thank you Andreas and Ted for the explanations and comments. Yes, I see both of your points now. Though we may reduce the mbcache overhead, due to the overhead of additional xattr I/O it would be better to provide some data to help users or distros to determine whether they will be better off completely disabling SELinux or increasing the inode size. I will go ahead and run the suggested experiments and get back with the results. Thanks, Mak. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
