linux-kernel - Re: [PATCH v1] mm/memory_hotplug: Easier calculation to get pages to next section boundary

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Message-ID: <20200205235007.GA28870@richard>
Date:   Thu, 6 Feb 2020 07:50:08 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     Wei Yang <richardw.yang@...ux.intel.com>
Cc:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Oscar Salvador <osalvador@...e.de>, Baoquan He <bhe@...hat.com>
Subject: Re: [PATCH v1] mm/memory_hotplug: Easier calculation to get pages to
 next section boundary

On Thu, Feb 06, 2020 at 07:19:45AM +0800, Wei Yang wrote:
>On Wed, Feb 05, 2020 at 02:52:51PM +0100, David Hildenbrand wrote:
>>Let's use a calculation that's easier to understand and calculates the
>>same result. Reusing existing macros makes this look nicer.
>>
>>We always want to have the number of pages (> 0) to the next section
>>boundary, starting from the current pfn.
>>
>>Suggested-by: Segher Boessenkool <segher@...nel.crashing.org>
>>Cc: Andrew Morton <akpm@...ux-foundation.org>
>>Cc: Michal Hocko <mhocko@...nel.org>
>>Cc: Oscar Salvador <osalvador@...e.de>
>>Cc: Baoquan He <bhe@...hat.com>
>>Cc: Wei Yang <richardw.yang@...ux.intel.com>
>>Signed-off-by: David Hildenbrand <david@...hat.com>
>
>Reviewed-by: Wei Yang <richardw.yang@...ux.intel.com>
>
>BTW, I got one question about hotplug size requirement.
>
>I thought the hotplug range should be section size aligned, while taking a
>look into current code function check_hotplug_memory_range() guard the range.
>
>This function says the range should be block_size aligned. And if I am
>correct, block size on x86 should be in the range
>
>    [MIN_MEMORY_BLOCK_SIZE, MEM_SIZE_FOR_LARGE_BLOCK]
>    
>And MIN_MEMORY_BLOCK_SIZE is section size.
>
>Seems currently we support subsection hotplug? Then how a subsection range got
>hotplug? Or this patch is a pre-requisite?
>

One more question is we support hot-add subsection memory but not support
hot-online subsection memory.

Is my understanding correct?

-- 
Wei Yang
Help you, Help me