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Re: [Xen-devel] [PATCH v5 1/2] memory_hotplug: Free pages as higher order

On 2018-10-10 13:37, Oscar Salvador wrote:
On Fri, Oct 05, 2018 at 01:40:05PM +0530, Arun KS wrote:
When free pages are done with higher order, time spend on
coalescing pages by buddy allocator can be reduced. With
section size of 256MB, hot add latency of a single section
shows improvement from 50-60 ms to less than 1 ms, hence
improving the hot add latency by 60%. Modify external
providers of online callback to align with the change.

Hi Arun, out of curiosity:

could you please explain how exactly did you mesure the speed

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index e379e85..2416136 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -690,9 +690,13 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
                        void *arg)
        unsigned long onlined_pages = *(unsigned long *)arg;
+       u64 t1, t2;

+       t1 = local_clock();
        if (PageReserved(pfn_to_page(start_pfn)))
onlined_pages = online_pages_blocks(start_pfn, nr_pages);
+       t2 = local_clock();
+       trace_printk("time spend = %llu us\n", (t2-t1)/(1000));

        online_mem_sections(start_pfn, start_pfn + nr_pages);



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