Re: [PATCH v1 7/8] mm: zswap: Optimally place members of struct zswap_pool, struct zswap_entry.

[Yosry Ahmed]

On Thu, Oct 08, 2026 at 11:28:13AM -0700, Kanchana P. Sridhar wrote:
> Place and align the members of struct zswap_pool and struct zswap_entry
> such that members used together in compress/decompress hot paths are
> able to share the same cacheline. Minimize holes within these structs
> while doing so.
> 
> Signed-off-by: Kanchana P. Sridhar <kanchanapsridhar2026@xxxxxxxxx>
> ---
>  mm/zswap.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 8ae67fd10522..ade84ac4076e 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -160,11 +160,11 @@ struct crypto_acomp_ctx {
>  struct zswap_pool {
>  	struct zs_pool *zs_pool;
>  	struct crypto_acomp_ctx __percpu *acomp_ctx;
> -	u8 compr_batch_size;
>  	struct percpu_ref ref;
> -	struct rcu_work release_rwork;
> -	struct hlist_node node;
>  	u8 idx;
> +	u8 compr_batch_size;
> +	struct hlist_node node;
> +	struct rcu_work release_rwork;

compr_batch_size is added by this series, why not just add it before idx
to begin with?

>  	char tfm_name[CRYPTO_MAX_ALG_NAME];
>  };
>  
> @@ -202,10 +202,10 @@ static struct shrinker *zswap_shrinker;
>   *              logic if referenced is unset. See comments in the shrinker
>   *              section for context.
>   * nid - NUMA node id of the page for which this is the zswap entry.
> - * pool_idx - id of the zswap_pool that the entry's data is in.
>   * handle - zsmalloc allocation handle that stores the compressed page data
>   * objcg - the obj_cgroup that the compressed memory is charged to
>   * lru - handle to the pool's lru used to evict pages.
> + * pool_idx - id of the zswap_pool that the entry's data is in.
>   */
>  struct zswap_entry {
>  	swp_entry_t swpentry;
> @@ -214,10 +214,10 @@ struct zswap_entry {
>  		bool referenced:1;
>  	};
>  	int nid;
> -	u8 pool_idx;
>  	unsigned long handle;
>  	struct obj_cgroup *objcg;
>  	struct list_head lru;
> +	u8 pool_idx;

As mentioned previously, this needs to be packed with the length.

>  };
>  
>  /*
> -- 
> 2.39.5
>