On Wed, 31 Mar 2021 08:38:05 +0100 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Mar 30, 2021 at 08:51:54PM +0200, Jesper Dangaard Brouer wrote: > > On Mon, 29 Mar 2021 13:06:42 +0100 > > Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > This series requires patches in Andrew's tree so the series is also > > > available at > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git mm-percpu-local_lock-v1r15 > > > > > > tldr: Jesper and Chuck, it would be nice to verify if this series helps > > > the allocation rate of the bulk page allocator. RT people, this > > > *partially* addresses some problems PREEMPT_RT has with the page > > > allocator but it needs review. > > > > I've run a new micro-benchmark[1] which shows: > > (CPU: Intel(R) Xeon(R) CPU E5-1650 v4 @ 3.60GHz) > > > > <Editting to focus on arrays> > > BASELINE > > single_page alloc+put: 194 cycles(tsc) 54.106 ns > > > > ARRAY variant: time_bulk_page_alloc_free_array: step=bulk size > > > > Per elem: 195 cycles(tsc) 54.225 ns (step:1) > > Per elem: 127 cycles(tsc) 35.492 ns (step:2) > > Per elem: 117 cycles(tsc) 32.643 ns (step:3) > > Per elem: 111 cycles(tsc) 30.992 ns (step:4) > > Per elem: 106 cycles(tsc) 29.606 ns (step:8) > > Per elem: 102 cycles(tsc) 28.532 ns (step:16) > > Per elem: 99 cycles(tsc) 27.728 ns (step:32) > > Per elem: 98 cycles(tsc) 27.252 ns (step:64) > > Per elem: 97 cycles(tsc) 27.090 ns (step:128) > > > > This should be seen in comparison with the older micro-benchmark[2] > > done on branch mm-bulk-rebase-v5r9. > > > > BASELINE > > single_page alloc+put: Per elem: 199 cycles(tsc) 55.472 ns > > > > ARRAY variant: time_bulk_page_alloc_free_array: step=bulk size > > > > Per elem: 202 cycles(tsc) 56.383 ns (step:1) > > Per elem: 144 cycles(tsc) 40.047 ns (step:2) > > Per elem: 134 cycles(tsc) 37.339 ns (step:3) > > Per elem: 128 cycles(tsc) 35.578 ns (step:4) > > Per elem: 120 cycles(tsc) 33.592 ns (step:8) > > Per elem: 116 cycles(tsc) 32.362 ns (step:16) > > Per elem: 113 cycles(tsc) 31.476 ns (step:32) > > Per elem: 110 cycles(tsc) 30.633 ns (step:64) > > Per elem: 110 cycles(tsc) 30.596 ns (step:128) > > > > Ok, so bulk allocation is faster than allocating single pages, no surprise > there. Putting the array figures for bulk allocation into tabular format > and comparing we get; > > Array variant (time to allocate a page in nanoseconds, lower is better) > Baseline Patched > 1 56.383 54.225 (+3.83%) > 2 40.047 35.492 (+11.38%) > 3 37.339 32.643 (+12.58%) > 4 35.578 30.992 (+12.89%) > 8 33.592 29.606 (+11.87%) > 16 32.362 28.532 (+11.85%) > 32 31.476 27.728 (+11.91%) > 64 30.633 27.252 (+11.04%) > 128 30.596 27.090 (+11.46%) > > The series is 11-12% faster when allocating multiple pages. That's a > fairly positive outcome and I'll include this in the series leader if > you have no objections. That is fine by me to add this to the cover letter. I like your tabular format as it makes is easier to compare. If you use the nanosec measurements and not the cycles, you should state that this was run on a CPU E5-1650 v4 @ 3.60GHz. You might notice that the factor between cycles(tsc) and ns is very close to 3.6. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
