On Thu, Mar 25, 2021 at 02:26:24PM +0000, Mel Gorman wrote: > On Thu, Mar 25, 2021 at 03:06:57PM +0100, Uladzislau Rezki wrote: > > > On Thu, Mar 25, 2021 at 12:50:01PM +0000, Matthew Wilcox wrote: > > > > 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.ga10...@pc638.lan/ > > > > > > > > > > That's fairly promising. Assuming the bulk allocator gets merged, it would > > > make sense to add vmalloc on top. That's for bringing it to my attention > > > because it's far more relevant than my imaginary potential use cases. > > > > > For the vmalloc we should be able to allocating on a specific NUMA node, > > at least the current interface takes it into account. As far as i see > > the current interface allocate on a current node: > > > > static inline unsigned long > > alloc_pages_bulk_array(gfp_t gfp, unsigned long nr_pages, struct page > > **page_array) > > { > > return __alloc_pages_bulk(gfp, numa_mem_id(), NULL, nr_pages, NULL, > > page_array); > > } > > > > Or am i missing something? > > > > No, you're not missing anything. Options would be to add a helper similar > alloc_pages_node or to directly call __alloc_pages_bulk specifying a node > and using GFP_THISNODE. prepare_alloc_pages() should pick the correct > zonelist containing only the required node. > IMHO, a helper something like *_node() would be reasonable. I see that many functions in "mm" have its own variants which explicitly add "_node()" prefix to signal to users that it is a NUMA aware calls.
As for __alloc_pages_bulk(), i got it. Thanks! -- Vlad Rezki
