linux-kernel - Re: [PATCH v2 5/5] mm: add per-order mTHP swpin

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Date: Wed, 10 Apr 2024 16:15:38 -0700
From: SeongJae Park <sj@...nel.org>
To: Barry Song <21cnbao@...il.com>
Cc: SeongJae Park <sj@...nel.org>,
	akpm@...ux-foundation.org,
	linux-mm@...ck.org,
	baolin.wang@...ux.alibaba.com,
	chrisl@...nel.org,
	david@...hat.com,
	hanchuanhua@...o.com,
	hannes@...xchg.org,
	hughd@...gle.com,
	kasong@...cent.com,
	ryan.roberts@....com,
	surenb@...gle.com,
	v-songbaohua@...o.com,
	willy@...radead.org,
	xiang@...nel.org,
	ying.huang@...el.com,
	yosryahmed@...gle.com,
	yuzhao@...gle.com,
	ziy@...dia.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] mm: add per-order mTHP swpin_refault counter

Hi Barry,

On Tue,  9 Apr 2024 20:26:31 +1200 Barry Song <21cnbao@...il.com> wrote:

> From: Barry Song <v-songbaohua@...o.com>
> 
> Currently, we are handling the scenario where we've hit a
> large folio in the swapcache, and the reclaiming process
> for this large folio is still ongoing.
> 
> Signed-off-by: Barry Song <v-songbaohua@...o.com>
> ---
>  include/linux/huge_mm.h | 1 +
>  mm/huge_memory.c        | 2 ++
>  mm/memory.c             | 1 +
>  3 files changed, 4 insertions(+)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index c8256af83e33..b67294d5814f 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -269,6 +269,7 @@ enum mthp_stat_item {
>  	MTHP_STAT_ANON_ALLOC_FALLBACK,
>  	MTHP_STAT_ANON_SWPOUT,
>  	MTHP_STAT_ANON_SWPOUT_FALLBACK,
> +	MTHP_STAT_ANON_SWPIN_REFAULT,
>  	__MTHP_STAT_COUNT
>  };
>  
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index d8d2ed80b0bf..fb95345b0bde 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -556,12 +556,14 @@ DEFINE_MTHP_STAT_ATTR(anon_alloc, MTHP_STAT_ANON_ALLOC);
>  DEFINE_MTHP_STAT_ATTR(anon_alloc_fallback, MTHP_STAT_ANON_ALLOC_FALLBACK);
>  DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
>  DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBACK);
> +DEFINE_MTHP_STAT_ATTR(anon_swpin_refault, MTHP_STAT_ANON_SWPIN_REFAULT);
>  
>  static struct attribute *stats_attrs[] = {
>  	&anon_alloc_attr.attr,
>  	&anon_alloc_fallback_attr.attr,
>  	&anon_swpout_attr.attr,
>  	&anon_swpout_fallback_attr.attr,
> +	&anon_swpin_refault_attr.attr,
>  	NULL,
>  };
>  
> diff --git a/mm/memory.c b/mm/memory.c
> index 9818dc1893c8..acc023795a4d 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4167,6 +4167,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>  		nr_pages = nr;
>  		entry = folio->swap;
>  		page = &folio->page;
> +		count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_SWPIN_REFAULT);
>  	}

>From the latest mm-unstable tree, I get below kunit build failure and
'git bisect' points this patch.

    $ ./tools/testing/kunit/kunit.py run --build_dir ../kunit.out/
    [16:07:40] Configuring KUnit Kernel ...
    [16:07:40] Building KUnit Kernel ...
    Populating config with:
    $ make ARCH=um O=../kunit.out/ olddefconfig
    Building with:
    $ make ARCH=um O=../kunit.out/ --jobs=36
    ERROR:root:.../mm/memory.c: In function ‘do_swap_page’:
    .../mm/memory.c:4169:17: error: implicit declaration of function ‘count_mthp_stat’ [-Werror=implicit-function-declaration]
     4169 |                 count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_SWPIN_REFAULT);
          |                 ^~~~~~~~~~~~~~~
    .../mm/memory.c:4169:53: error: ‘MTHP_STAT_ANON_SWPIN_REFAULT’ undeclared (first use in this function)
     4169 |                 count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_SWPIN_REFAULT);
          |                                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
    .../mm/memory.c:4169:53: note: each undeclared identifier is reported only once for each function it appears in
    cc1: some warnings being treated as errors

My kunit build config doesn't have CONFIG_TRANSPARE_HUGEPAGE.  Maybe that's the
reason and this patch, or the patch that introduced the function and the enum
need to take care of the case?


Thanks,
SJ

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