linux-kernel - Re: [PATCH mm-unstable 4/4] mm: multi-gen LRU: cleanup lru_gen_test

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Message-ID: <CAJj2-QHSBPNhuM2EY3Hki=-Xq_H-k2zutm7xJGCP+fCqfCqt1g@mail.gmail.com>
Date:   Thu, 1 Jun 2023 16:02:58 +0800
From:   Yuanchu Xie <yuanchu@...gle.com>
To:     "T.J. Alumbaugh" <talumbau@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Yu Zhao <yuzhao@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-mm@...gle.com
Subject: Re: [PATCH mm-unstable 4/4] mm: multi-gen LRU: cleanup lru_gen_test_recent()

On Mon, May 22, 2023 at 7:21 PM T.J. Alumbaugh <talumbau@...gle.com> wrote:
>
> Avoid passing memcg* and pglist_data* to lru_gen_test_recent()
> since we only use the lruvec anyway.
>
> Signed-off-by: T.J. Alumbaugh <talumbau@...gle.com>
> ---
>  mm/workingset.c | 46 ++++++++++++++++------------------------------
>  1 file changed, 16 insertions(+), 30 deletions(-)
>
> diff --git a/mm/workingset.c b/mm/workingset.c
> index 90ae785d4c9c..5796e927e6d7 100644
> --- a/mm/workingset.c
> +++ b/mm/workingset.c
> @@ -257,59 +257,46 @@ static void *lru_gen_eviction(struct folio *folio)
>
>  /*
>   * Tests if the shadow entry is for a folio that was recently evicted.
> - * Fills in @memcgid, @pglist_data, @token, @workingset with the values
> - * unpacked from shadow.
> + * Fills in @lruvec, @token, @workingset with the values unpacked from shadow.
>   */
> -static bool lru_gen_test_recent(void *shadow, bool file, int *memcgid,
> -               struct pglist_data **pgdat, unsigned long *token, bool *workingset)
> +static bool lru_gen_test_recent(void *shadow, bool file, struct lruvec **lruvec,
> +                               unsigned long *token, bool *workingset)
>  {
> -       struct mem_cgroup *eviction_memcg;
> -       struct lruvec *lruvec;
> -       struct lru_gen_folio *lrugen;
> +       int memcg_id;
>         unsigned long min_seq;
> +       struct mem_cgroup *memcg;
> +       struct pglist_data *pgdat;
>
> -       unpack_shadow(shadow, memcgid, pgdat, token, workingset);
> -       eviction_memcg = mem_cgroup_from_id(*memcgid);
> +       unpack_shadow(shadow, &memcg_id, &pgdat, token, workingset);
>
> -       lruvec = mem_cgroup_lruvec(eviction_memcg, *pgdat);
> -       lrugen = &lruvec->lrugen;
> +       memcg = mem_cgroup_from_id(memcg_id);
> +       *lruvec = mem_cgroup_lruvec(memcg, pgdat);
>
> -       min_seq = READ_ONCE(lrugen->min_seq[file]);
> +       min_seq = READ_ONCE((*lruvec)->lrugen.min_seq[file]);
>         return (*token >> LRU_REFS_WIDTH) == (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH));
>  }
>
>  static void lru_gen_refault(struct folio *folio, void *shadow)
>  {
>         int hist, tier, refs;
> -       int memcg_id;
>         bool workingset;
>         unsigned long token;
> -       unsigned long min_seq;
>         struct lruvec *lruvec;
>         struct lru_gen_folio *lrugen;
> -       struct mem_cgroup *memcg;
> -       struct pglist_data *pgdat;
>         int type = folio_is_file_lru(folio);
>         int delta = folio_nr_pages(folio);
>
>         rcu_read_lock();
>
> -       if (!lru_gen_test_recent(shadow, type, &memcg_id, &pgdat, &token,
> -                       &workingset))
> +       if (!lru_gen_test_recent(shadow, type, &lruvec, &token, &workingset))
>                 goto unlock;
>
> -       memcg = folio_memcg_rcu(folio);
> -       if (memcg_id != mem_cgroup_id(memcg))
> +       if (lruvec != folio_lruvec(folio))
>                 goto unlock;
>
> -       if (pgdat != folio_pgdat(folio))
> -               goto unlock;
> -
> -       lruvec = mem_cgroup_lruvec(memcg, pgdat);
>         lrugen = &lruvec->lrugen;
> -       min_seq = READ_ONCE(lrugen->min_seq[type]);
>
> -       hist = lru_hist_from_seq(min_seq);
> +       hist = lru_hist_from_seq(READ_ONCE(lrugen->min_seq[type]));
>         /* see the comment in folio_lru_refs() */
>         refs = (token & (BIT(LRU_REFS_WIDTH) - 1)) + workingset;
>         tier = lru_tier_from_refs(refs);
> @@ -339,8 +326,8 @@ static void *lru_gen_eviction(struct folio *folio)
>         return NULL;
>  }
>
> -static bool lru_gen_test_recent(void *shadow, bool file, int *memcgid,
> -               struct pglist_data **pgdat, unsigned long *token, bool *workingset)
> +static bool lru_gen_test_recent(void *shadow, bool file, struct lruvec **lruvec,
> +                               unsigned long *token, bool *workingset)
>  {
>         return false;
>  }
> @@ -435,8 +422,7 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset)
>         unsigned long eviction;
>
>         if (lru_gen_enabled())
> -               return lru_gen_test_recent(shadow, file, &memcgid, &pgdat, &eviction,
> -                       workingset);
> +               return lru_gen_test_recent(shadow, file, &eviction_lruvec, &eviction, workingset);
>
>         unpack_shadow(shadow, &memcgid, &pgdat, &eviction, workingset);
>         eviction <<= bucket_order;
> --
> 2.40.1.698.g37aff9b760-goog
>
Reviewed-by: Yuanchu Xie <yuanchu@...gle.com>