On Wed, Aug 04, 2010 at 09:04:03AM +0800, Zhang, Yanmin wrote: > We ran lots of benchmarks on many machines. Below is something to > share with you. > > Improvement: > 1) We get about 30% improvement with kbuild workload on Nehalem > machines. It's hard to improve kbuild performance. Your tree does. > > Issues: > 1) Compiling fails on a couple of file systems, such like CONFIG_ISO9660_FS=y. > 2) dbenchthreads has about 50% regression. We connect a JBOD of 12 disks to > a machine. Start 4 dbench threads per disk. We run the workload under > a regular user account. If we run it under root account, we get 22% > improvement instead of regression. The root cause is ACL checking. > With your patch, do_path_lookup firstly goes through rcu steps which > including a exec permission checking. With ACL, the __exec_permission > always fails. Then a later nameidata_drop_rcu often fails as > dentry->d_seq is changed. Oh one other thing I wanted to ask about. d_seq changing should not be too common. If the directory is renamed, or if it is turned negative should be the only cases in which we should see a d_seq changes. Or unless there is a bug and it is checking the wrong sequence or against the wrong dentry. How often would you say nameidata_drop_rcu fails (without the following acl rcu patches)? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>