RE: [RFC PATCH 5/5] mm, page_alloc: Introduce ZONELIST_FALLBACK_SAME_TYPE fallback list

["Du, Fan" <fan.du@intel.com>]

>-----Original Message-----
>From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On
>Behalf Of Michal Hocko
>Sent: Thursday, April 25, 2019 4:43 PM
>To: Du, Fan <fan.du@intel.com>
>Cc: akpm@linux-foundation.org; Wu, Fengguang <fengguang.wu@intel.com>;
>Williams, Dan J <dan.j.williams@intel.com>; Hansen, Dave
><dave.hansen@intel.com>; xishi.qiuxishi@alibaba-inc.com; Huang, Ying
><ying.huang@intel.com>; linux-mm@kvack.org; linux-kernel@vger.kernel.org
>Subject: Re: [RFC PATCH 5/5] mm, page_alloc: Introduce
>ZONELIST_FALLBACK_SAME_TYPE fallback list
>
>On Thu 25-04-19 08:20:28, Du, Fan wrote:
>>
>>
>> >-----Original Message-----
>> >From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On
>> >Behalf Of Michal Hocko
>> >Sent: Thursday, April 25, 2019 4:10 PM
>> >To: Du, Fan <fan.du@intel.com>
>> >Cc: akpm@linux-foundation.org; Wu, Fengguang
><fengguang.wu@intel.com>;
>> >Williams, Dan J <dan.j.williams@intel.com>; Hansen, Dave
>> ><dave.hansen@intel.com>; xishi.qiuxishi@alibaba-inc.com; Huang, Ying
>> ><ying.huang@intel.com>; linux-mm@kvack.org;
>linux-kernel@vger.kernel.org
>> >Subject: Re: [RFC PATCH 5/5] mm, page_alloc: Introduce
>> >ZONELIST_FALLBACK_SAME_TYPE fallback list
>> >
>> >On Thu 25-04-19 07:55:58, Du, Fan wrote:
>> >> >> PMEM is good for frequently read accessed page, e.g. page
>cache(implicit
>> >> >> page
>> >> >> request), or user space data base (explicit page request)
>> >> >> For now this patch create GFP_SAME_NODE_TYPE for such cases,
>> >additional
>> >> >> Implementation will be followed up.
>> >> >
>> >> >Then simply configure that NUMA node as movable and you get these
>> >> >allocations for any movable allocation. I am not really convinced a new
>> >> >gfp flag is really justified.
>> >>
>> >> Case 1: frequently write and/or read accessed page deserved to DRAM
>> >
>> >NUMA balancing
>>
>> Sorry, I mean page cache case here.
>> Numa balancing works for pages mapped in pagetable style.
>
>I would still expect that a remote PMEM node access latency is
>smaller/comparable to the real storage so a promoting part is not that
>important for the unmapped pagecache. Maybe I am wrong here but that
>really begs for some experiments before we start adding special casing.

I understand your concern :), please refer to following summary from 3rd party.
https://arxiv.org/pdf/1903.05714.pdf


>--
>Michal Hocko
>SUSE Labs