On Thu, Apr 20, 2017 at 08:50:43AM +0800, Huang, Ying wrote: > Johannes Weiner <han...@cmpxchg.org> writes: > > On Wed, Apr 19, 2017 at 03:06:24PM +0800, Huang, Ying wrote: > >> With the patchset, the swap out throughput improves 3.6% (from about > >> 4.16GB/s to about 4.31GB/s) in the vm-scalability swap-w-seq test case > >> with 8 processes. The test is done on a Xeon E5 v3 system. The swap > >> device used is a RAM simulated PMEM (persistent memory) device. To > >> test the sequential swapping out, the test case creates 8 processes, > >> which sequentially allocate and write to the anonymous pages until the > >> RAM and part of the swap device is used up. > >> > >> Cc: Johannes Weiner <han...@cmpxchg.org> > >> Signed-off-by: "Huang, Ying" <ying.hu...@intel.com> > >> Acked-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> [for > >> can_split_huge_page()] > > > > How often does this actually happen in practice? Because all that this > > protects us from is trying to allocate a swap cluster - which with the > > si->free_clusters list really isn't all that expensive - and return it > > again. Unless this happens all the time in practice, this optimization > > seems misplaced. > > To my surprise too, I found this patch has measurable impact in my > test. The swap out throughput improves 3.6% in the vm-scalability > swap-w-seq test case with 8 processes. Details are in the original > patch description.
Yeah I think that justifies it. The changelog says "the patchset", I didn't realize this is the gain from just this patch alone. Care to update that? Thanks!
