On Wed, Jan 11, 2017 at 02:27:12PM +0100, Jesper Dangaard Brouer wrote: > On Wed, 11 Jan 2017 13:44:20 +0100 > Jesper Dangaard Brouer <brouer@xxxxxxxxxx> wrote: > > > On Mon, 9 Jan 2017 16:35:17 +0000 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > The following is results from a page allocator micro-benchmark. Only > > > order-0 is interesting as higher orders do not use the per-cpu allocator > > > > Micro-benchmarked with [1] page_bench02: > > modprobe page_bench02 page_order=0 run_flags=$((2#010)) loops=$((10**8)); \ > > rmmod page_bench02 ; dmesg --notime | tail -n 4 > > > > Compared to baseline: 213 cycles(tsc) 53.417 ns > > - against this : 184 cycles(tsc) 46.056 ns > > - Saving : -29 cycles > > - Very close to expected 27 cycles saving [see below [2]] > > When perf benchmarking I noticed that the "summed" children perf > overhead from calling alloc_pages_current() is 65.05%. Compared to > "free-path" of summed 28.28% of calls "under" __free_pages(). > > This is caused by CONFIG_NUMA=y, as call path is long with NUMA > (and other helpers are also non-inlined calls): > > alloc_pages > -> alloc_pages_current > -> __alloc_pages_nodemask > -> get_page_from_freelist > > Without NUMA the call levels gets compacted by inlining to: > > __alloc_pages_nodemask > -> get_page_from_freelist > > After disabling NUMA, the split between alloc(48.80%) vs. free(42.67%) > side is more balanced. > > Saving by disabling CONFIG_NUMA of: > - CONFIG_NUMA=y : 184 cycles(tsc) 46.056 ns > - CONFIG_NUMA=n : 143 cycles(tsc) 35.913 ns > - Saving: : 41 cycles (approx 22%) > > I would conclude, there is room for improvements with CONFIG_NUMA code > path case. Lets followup on that in a later patch series... > Potentially. The NUMA paths do memory policy work and has more complexity in the statistics path. It may be possible to side-step some of it. There were not many safe options when I last looked but that was a long time ago. Most of the focus has been on the core allocator itself and not the wrappers around it. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>