linux-kernel - Re: [PATCH -V11 4/9] mm/migrate: demote pages during reclaim

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Date:   Wed, 21 Jul 2021 17:11:19 -0400
From:   Zi Yan <ziy@...dia.com>
To:     Huang Ying <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>, Wei Xu <weixugc@...gle.com>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Greg Thelen <gthelen@...gle.com>,
        Keith Busch <kbusch@...nel.org>
Subject: Re: [PATCH -V11 4/9] mm/migrate: demote pages during reclaim

On 21 Jul 2021, at 2:39, Huang Ying wrote:

> From: Dave Hansen <dave.hansen@...ux.intel.com>
>
> This is mostly derived from a patch from Yang Shi:
>
> 	https://lore.kernel.org/linux-mm/1560468577-101178-10-git-send-email-yang.shi@linux.alibaba.com/
>
> Add code to the reclaim path (shrink_page_list()) to "demote" data to
> another NUMA node instead of discarding the data.  This always avoids the
> cost of I/O needed to read the page back in and sometimes avoids the
> writeout cost when the page is dirty.
>
> A second pass through shrink_page_list() will be made if any demotions
> fail.  This essentially falls back to normal reclaim behavior in the case
> that demotions fail.  Previous versions of this patch may have simply
> failed to reclaim pages which were eligible for demotion but were unable
> to be demoted in practice.
>
> For some cases, for example, MADV_PAGEOUT, the pages are always discarded
> instead of demoted to follow the kernel API definition.  Because
> MADV_PAGEOUT is defined as freeing specified pages regardless in which
> tier they are.
>
> Note: This just adds the start of infrastructure for migration.  It is
> actually disabled next to the FIXME in migrate_demote_page_ok().
>
> Link: https://lkml.kernel.org/r/20210715055145.195411-5-ying.huang@intel.com
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Reviewed-by: Yang Shi <shy828301@...il.com>
> Reviewed-by: Wei Xu <weixugc@...gle.com>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Zi Yan <ziy@...dia.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Greg Thelen <gthelen@...gle.com>
> Cc: Keith Busch <kbusch@...nel.org>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
>  include/linux/migrate.h        |  9 ++++
>  include/trace/events/migrate.h |  3 +-
>  mm/vmscan.c                    | 85 ++++++++++++++++++++++++++++++++++
>  3 files changed, 96 insertions(+), 1 deletion(-)
>

LGTM. Reviewed-by: Zi Yan <ziy@...dia.com>

—
Best Regards,
Yan, Zi

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