On Thu, Mar 25, 2021 at 11:42:19AM +0000, Mel Gorman wrote: > This series introduces a bulk order-0 page allocator with sunrpc and > the network page pool being the first users. The implementation is not > efficient as semantics needed to be ironed out first. If no other semantic > changes are needed, it can be made more efficient. Despite that, this > is a performance-related for users that require multiple pages for an > operation without multiple round-trips to the page allocator. Quoting > the last patch for the high-speed networking use-case > > Kernel XDP stats CPU pps Delta > Baseline XDP-RX CPU total 3,771,046 n/a > List XDP-RX CPU total 3,940,242 +4.49% > Array XDP-RX CPU total 4,249,224 +12.68% > > >From the SUNRPC traces of svc_alloc_arg() > > Single page: 25.007 us per call over 532,571 calls > Bulk list: 6.258 us per call over 517,034 calls > Bulk array: 4.590 us per call over 517,442 calls > > Both potential users in this series are corner cases (NFS and high-speed > networks) so it is unlikely that most users will see any benefit in the > short term. Other potential other users are batch allocations for page > cache readahead, fault around and SLUB allocations when high-order pages > are unavailable. It's unknown how much benefit would be seen by converting > multiple page allocation calls to a single batch or what difference it may > make to headline performance. We have a third user, vmalloc(), with a 16% perf improvement. I know the email says 21% but that includes the 5% improvement from switching to kvmalloc() to allocate area->pages. https://lore.kernel.org/linux-mm/20210323133948.GA10046@xxxxxxxxx/ I don't know how many _frequent_ vmalloc users we have that will benefit from this, but it's probably more than will benefit from improvements to 200Gbit networking performance.
