linux-kernel - Re: [PATCH v3 8/8] mm/page_alloc: remove a wrapper for alloc_migration

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Date:   Mon, 6 Jul 2020 17:44:16 +0900
From:   Joonsoo Kim <js1304@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com,
        Christoph Hellwig <hch@...radead.org>,
        Roman Gushchin <guro@...com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Michal Hocko <mhocko@...e.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v3 8/8] mm/page_alloc: remove a wrapper for alloc_migration_target()

2020년 7월 4일 (토) 오전 1:18, Vlastimil Babka <vbabka@...e.cz>님이 작성:
>
> On 6/23/20 8:13 AM, js1304@...il.com wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@....com>
> >
> > There is a well-defined standard migration target callback.
> > Use it directly.
> >
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
>
> But you could move this to patch 5/8 to reduce churn. And do the same with

Yes, I now realize that it is possible to make this change earlier.
However, reordering
the patches would cause additional change so I will not change the
order in the next
version. Result would be the same. :)

> mm/memory-failure.c new_page() there really, to drop the simple wrappers. Only

Okay. As you suggested below, with NUMA_NO_NODE handling, we can remove
the more wrappers. I will do it.

> new_node_page() is complex enough.
> Hm wait, new_node_page() is only called by do_migrate_range() which is only
> called by __offline_pages() with explicit test that all pages are from a single
> zone, so the nmask could also be setup just once and not per each page, making
> it possible to remove the wrapper.

I have tried this suggestion and found that code is not simpler than before.
However, there would be minor performance benefit so I will include
this change, too.

> But for new_page() you would have to define that mtc->nid == NUMA_NO_NODE means
> alloc_migrate_target() does page_to_nid(page) by itself.

Yes, I will use this suggestion.

Thanks.