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

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Date:   Wed, 10 Oct 2018 16:21:16 +0530
From:   Arun KS <arunks@...eaurora.org>
To:     Oscar Salvador <osalvador@...hadventures.net>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        boris.ostrovsky@...cle.com, jgross@...e.com,
        akpm@...ux-foundation.org, dan.j.williams@...el.com,
        mhocko@...e.com, vbabka@...e.cz, iamjoonsoo.kim@....com,
        gregkh@...uxfoundation.org, osalvador@...e.de, malat@...ian.org,
        kirill.shutemov@...ux.intel.com, jrdr.linux@...il.com,
        yasu.isimatu@...il.com, mgorman@...hsingularity.net,
        aaron.lu@...el.com, devel@...uxdriverproject.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        xen-devel@...ts.xenproject.org, vatsa@...eaurora.org,
        vinmenon@...eaurora.org, getarunks@...il.com
Subject: Re: [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
> improvement?

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);


Regards,
Arun

> 
> Thanks