On Mon, May 31, 2021 at 05:23:38PM +0200, Jesper Dangaard Brouer wrote: > On Mon, 31 May 2021 13:04:12 +0100 > Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > > > The per-cpu page allocator (PCP) only stores order-0 pages. This means > > that all THP and "cheap" high-order allocations including SLUB contends > > on the zone->lock. This patch extends the PCP allocator to store THP and > > "cheap" high-order pages. Note that struct per_cpu_pages increases in > > size to 256 bytes (4 cache lines) on x86-64. > > > > Note that this is not necessarily a universal performance win because of > > how it is implemented. High-order pages can cause pcp->high to be exceeded > > prematurely for lower-orders so for example, a large number of THP pages > > being freed could release order-0 pages from the PCP lists. Hence, much > > depends on the allocation/free pattern as observed by a single CPU to > > determine if caching helps or hurts a particular workload. > > > > That said, basic performance testing passed. The following is a netperf > > UDP_STREAM test which hits the relevant patches as some of the network > > allocations are high-order. > > This series[1] looks very interesting! I confirm that some network > allocations do use high-order allocations. Thus, I think this will > increase network performance in general, like you confirm below: > Would you be able to do a small test on a real high-speed network? It's something I can do easily myself in a few weeks but I do not have testbed readily available at the moment. It's ok if you do not have the time, it would just be nice if I could include independent results in the changelog if the results are positive. Alternatively, a negative result would mean going back to the drawing board :) -- Mel Gorman SUSE Labs
