On Tue, Jun 17, 2014 at 06:37:59PM -0400, Waiman Long wrote: > In some architectures like x86, atomic_add() is a full memory > barrier. In that case, an additional smp_mb() is just a waste of time. > This patch replaces that smp_mb() by smp_mb__after_atomic() which > will avoid the redundant memory barrier in some architectures. > > With a 3.16-rc1 based kernel, this patch reduced the execution time > of breaking 1000 transparent huge pages from 38,245us to 30,964us. A > reduction of 19% which is quite sizeable. It also reduces the %cpu > time of the __split_huge_page_refcount function in the perf profile > from 2.18% to 1.15%. > > Signed-off-by: Waiman Long <Waiman.Long@xxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>