Re: [RFC PATCH 3/9] mm: zswap: refactor limit checking from zswap_store()

Chengming Zhou
2024-03-27T02:42:09Z

On 2024/3/26 07:50, Yosry Ahmed wrote:
> Refactor limit and acceptance threshold checking outside of
> zswap_store(). This code will be moved around in a following patch, so
> it would be cleaner to move a function call around.
>
> Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
> ---
> mm/zswap.c | 32 ++++++++++++++++----------------
> 1 file changed, 16 insertions(+), 16 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index ff1975afb7e3d..6b890c8590ef7 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1415,6 +1415,21 @@ static void zswap_fill_page(void *ptr, unsigned long value)
> memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
> }
>
> +static bool zswap_check_limit(void)
> +{
> + unsigned long cur_pages = zswap_total_pages();
> + unsigned long thr = zswap_accept_thr_pages();
> + unsigned long max_pages = zswap_max_pages();
> +
> + if (cur_pages >= max_pages) {
> + zswap_pool_limit_hit++;
> + zswap_pool_reached_full = true;
> + } else if (zswap_pool_reached_full && cur_pages <= thr) {
> + zswap_pool_reached_full = false;
> + }
> + return !zswap_pool_reached_full;

nit: Then we use "!zswap_check_limit()" below, double negation looks complex,
should we change to zswap_should_reject() or something?

> +}
> +
> bool zswap_store(struct folio *folio)
> {
> swp_entry_t swp = folio->swap;
> @@ -1422,7 +1437,6 @@ bool zswap_store(struct folio *folio)
> struct xarray *tree = swap_zswap_tree(swp);
> struct obj_cgroup *objcg = NULL;
> struct mem_cgroup *memcg = NULL;
> - unsigned long max_pages, cur_pages;
> struct zswap_entry *entry;
>
> VM_WARN_ON_ONCE(!folio_test_locked(folio));
> @@ -1446,22 +1460,8 @@ bool zswap_store(struct folio *folio)
> mem_cgroup_put(memcg);
> }
>
> - /* Check global limits */
> - cur_pages = zswap_total_pages();
> - max_pages = zswap_max_pages();
> -
> - if (cur_pages >= max_pages) {
> - zswap_pool_limit_hit++;
> - zswap_pool_reached_full = true;
> + if (!zswap_check_limit())
> goto reject;
> - }
> -
> - if (zswap_pool_reached_full) {
> - if (cur_pages > zswap_accept_thr_pages())
> - goto reject;
> - else
> - zswap_pool_reached_full = false;
> - }
>
> /* allocate entry */
> entry = zswap_entry_cache_alloc(GFP_KERNEL, folio_nid(folio));