On Sat, Feb 18, 2023 at 11:33:16PM -0800, Nhat Pham wrote:
> +++ b/mm/workingset.c
> @@ -244,6 +244,30 @@ static void *lru_gen_eviction(struct folio *folio)
> return pack_shadow(mem_cgroup_id(memcg), pgdat, token, refs);
> }
>
> +/*
> + * Test if the folio is recently evicted.
> + *
> + * As a side effect, also populates the references with
> + * values unpacked from the shadow of the evicted folio.
> + */
I find this comment hard to understand. First it talks about "the
folio", but it doesn't pass a folio. Then it talks about "the
references", but I don't have any idea what those are either.
I think what you mean is,
* Test if the shadow entry is for a folio which was recently evicted.
* Fills in @memcgid, @pgdat, @token and @workingset with values
* extracted from the shadow entry.
> +static bool lru_gen_test_recent(void *shadow, bool file, int *memcgid,
> + struct pglist_data **pgdat, unsigned long *token, bool *workingset)
> +{
> + struct mem_cgroup *eviction_memcg;
> + struct lruvec *lruvec;
> + struct lru_gen_struct *lrugen;
> + unsigned long min_seq;
> +
> + unpack_shadow(shadow, memcgid, pgdat, token, workingset);
> + eviction_memcg = mem_cgroup_from_id(*memcgid);
> +
> + lruvec = mem_cgroup_lruvec(eviction_memcg, *pgdat);
> + lrugen = &lruvec->lrugen;
> +
> + min_seq = READ_ONCE(lrugen->min_seq[file]);
> + return (*token >> LRU_REFS_WIDTH) == (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH));
> +}
[...]
> +/*
> + * Test if the folio is recently evicted by checking if
> + * refault distance of shadow exceeds workingset size.
> *
> - * Calculates and evaluates the refault distance of the previously
> - * evicted folio in the context of the node and the memcg whose memory
> - * pressure caused the eviction.
> + * As a side effect, populate workingset with the value
> + * unpacked from shadow.
> */
1. Shouldn't this be kernel-doc?
2. Again, don't use the term "side effect" here. It's just one of
the things that the function _does_.
