Re: [RFC Get rid of shrink code - memory-hotplug]

[Vlastimil Babka <vbabka@suse.cz>]

On 12/5/18 8:12 PM, Michal Hocko wrote:
> [Cc Vlastimil]
> 
> On Tue 04-12-18 13:43:31, osalvador@suse.de wrote:
>> On 2018-12-04 12:31, David Hildenbrand wrote:
>>  > If I am not wrong, zone_contiguous is a pure mean for performance
>>> improvement, right? So leaving zone_contiguous unset is always save. I
>>> always disliked the whole clear/set_zone_contiguous thingy. I wonder if
>>> we can find a different way to boost performance there (in the general
>>> case). Or is this (zone_contiguous) even worth keeping around at all for
>>> now? (do we have performance numbers?)
>>
>> It looks like it was introduced by 7cf91a98e607
>> ("mm/compaction: speed up pageblock_pfn_to_page() when zone is contiguous").
>>
>> The improve numbers are in the commit.
>> So I would say that we need to keep it around.
> 
> Is that still the case though?

Well, __pageblock_pfn_to_page() has to be called for each pageblock in
compaction, when zone_contiguous is false. And that's unchanged since
the introduction of zone_contiguous, so the numbers should still hold.