On Wed, Aug 18, 2010 at 02:54:56PM -0400, J. Bruce Fields wrote: > On Wed, Aug 18, 2010 at 07:50:40PM +0200, Andi Kleen wrote: > > > - nfsd updates it whenever it reads an mtime out of an inode that matches > > > current_fs_time to the granularity of 1/HZ. > > > > That means you have a very very hot cache line on a larger system > > if there are a lot of mtime changes. Probably a bad idea. > > Only if those mtime changes are also followed immediately by nfsd reads > of the mtime. If multiple writers are changing the same location in quick succession you have a hot cache line that gets bounced around. It doesn't need reads, although reads make it even worse. There's a lot of effort currently to make the VFS more parallel and less synchronized and it would be bad again to regress here again. -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
