Re: [PATCHv4 6/9] zsmalloc: pass limit on pages per-zspage to zs_create_pool()

Minchan Kim
2022-11-11T02:10:41Z

On Mon, Oct 31, 2022 at 02:41:05PM +0900, Sergey Senozhatsky wrote:
> Allow zsmalloc pool owner to specify max number of pages
> per-zspage (during pool creation), so that different pools
> can have different characteristics.
>
> By default we pass ZS_DEFAULT_PAGES_PER_ZSPAGE which is 4
> (matches the current order 2 zspages limit).

How could user decide what's the best size for their workload?

>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
> drivers/block/zram/zram_drv.c | 3 ++-
> include/linux/zsmalloc.h | 2 +-
> mm/zsmalloc.c | 11 +++++++----
> 3 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 90b0c66bbd5b..bec02f636bce 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1247,7 +1247,8 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
> if (!zram->table)
> return false;
>
> - zram->mem_pool = zs_create_pool(zram->disk->disk_name);
> + zram->mem_pool = zs_create_pool(zram->disk->disk_name,
> + ZS_DEFAULT_PAGES_PER_ZSPAGE);
> if (!zram->mem_pool) {
> vfree(zram->table);
> return false;
> diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
> index b6b8654a2d45..28f2b9cb1c47 100644
> --- a/include/linux/zsmalloc.h
> +++ b/include/linux/zsmalloc.h
> @@ -50,7 +50,7 @@ struct zs_pool_stats {
>
> struct zs_pool;
>
> -struct zs_pool *zs_create_pool(const char *name);
> +struct zs_pool *zs_create_pool(const char *name, unsigned long num_pages);
> void zs_destroy_pool(struct zs_pool *pool);
>
> unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t flags);
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index d329bd673baa..42987a913f45 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -366,7 +366,7 @@ static void *zs_zpool_create(const char *name, gfp_t gfp,
> * different contexts and its caller must provide a valid
> * gfp mask.
> */
> - return zs_create_pool(name);
> + return zs_create_pool(name, ZS_DEFAULT_PAGES_PER_ZSPAGE);
> }
>
> static void zs_zpool_destroy(void *pool)
> @@ -2195,6 +2195,7 @@ static int zs_register_shrinker(struct zs_pool *pool)
> /**
> * zs_create_pool - Creates an allocation pool to work from.
> * @name: pool name to be created
> + * @num_pages: maximum number of pages per-zspage

How about "max_page_chain:"?

> *
> * This function must be called before anything when using
> * the zsmalloc allocator.
> @@ -2202,18 +2203,20 @@ static int zs_register_shrinker(struct zs_pool *pool)
> * On success, a pointer to the newly created pool is returned,
> * otherwise NULL.
> */
> -struct zs_pool *zs_create_pool(const char *name)
> +struct zs_pool *zs_create_pool(const char *name, unsigned long num_pages)
> {
> int i;
> struct zs_pool *pool;
> struct size_class *prev_class = NULL;
> - unsigned long num_pages;
> +
> + if (WARN_ON(num_pages < ZS_MIN_PAGES_PER_ZSPAGE ||
> + num_pages > ZS_MAX_PAGES_PER_ZSPAGE))
> + return NULL;
>
> pool = kzalloc(sizeof(*pool), GFP_KERNEL);
> if (!pool)
> return NULL;
>
> - num_pages = ZS_DEFAULT_PAGES_PER_ZSPAGE;
> /* min_alloc_size must be multiple of ZS_ALIGN */
> pool->min_alloc_size = num_pages << PAGE_SHIFT >> OBJ_INDEX_BITS;
> pool->min_alloc_size = max(pool->min_alloc_size, ZS_MIN_ALLOC_SIZE);
> --
> 2.38.1.273.g43a17bfeac-goog
>