On Tue, 1 Jun 2021 13:45:33 +0100 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > 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. I don't have time right now. If others have time, you can use this git tree provided by Mel: https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git/ git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git branch: mm-pcphighorder-v1r7 > Alternatively, a negative result would mean going back to the drawing > board :) I'm confident that this will be a positive performance change. (I remember we played with similar patches back in 2017). -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
