On Fri, Nov 18, 2022 at 10:24:07AM -0800, Nhat Pham wrote:
> This commit adds the writeback mechanism for zsmalloc, analogous to the
> zbud allocator. Zsmalloc will attempt to determine the coldest zspage
> (i.e least recently used) in the pool, and attempt to write back all the
> stored compressed objects via the pool's evict handler.
>
> Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
> ---
> mm/zsmalloc.c | 193 +++++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 182 insertions(+), 11 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 3ff86f57d08c..d73b9f9e9adf 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -271,12 +271,13 @@ struct zspage {
> #ifdef CONFIG_ZPOOL
> /* links the zspage to the lru list in the pool */
> struct list_head lru;
> + bool under_reclaim;
> + /* list of unfreed handles whose objects have been reclaimed */
> + unsigned long *deferred_handles;
> #endif
>
> struct zs_pool *pool;
> -#ifdef CONFIG_COMPACTION
> rwlock_t lock;
> -#endif
> };
>
> struct mapping_area {
> @@ -297,10 +298,11 @@ static bool ZsHugePage(struct zspage *zspage)
> return zspage->huge;
> }
>
> -#ifdef CONFIG_COMPACTION
> static void migrate_lock_init(struct zspage *zspage);
> static void migrate_read_lock(struct zspage *zspage);
> static void migrate_read_unlock(struct zspage *zspage);
> +
> +#ifdef CONFIG_COMPACTION
> static void migrate_write_lock(struct zspage *zspage);
> static void migrate_write_lock_nested(struct zspage *zspage);
> static void migrate_write_unlock(struct zspage *zspage);
> @@ -308,9 +310,6 @@ static void kick_deferred_free(struct zs_pool *pool);
> static void init_deferred_free(struct zs_pool *pool);
> static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
> #else
> -static void migrate_lock_init(struct zspage *zspage) {}
> -static void migrate_read_lock(struct zspage *zspage) {}
> -static void migrate_read_unlock(struct zspage *zspage) {}
> static void migrate_write_lock(struct zspage *zspage) {}
> static void migrate_write_lock_nested(struct zspage *zspage) {}
> static void migrate_write_unlock(struct zspage *zspage) {}
> @@ -425,6 +424,27 @@ static void zs_zpool_free(void *pool, unsigned long handle)
> zs_free(pool, handle);
> }
>
> +static int zs_reclaim_page(struct zs_pool *pool, unsigned int retries);
> +
> +static int zs_zpool_shrink(void *pool, unsigned int pages,
> + unsigned int *reclaimed)
> +{
> + unsigned int total = 0;
> + int ret = -EINVAL;
> +
> + while (total < pages) {
> + ret = zs_reclaim_page(pool, 8);
> + if (ret < 0)
> + break;
> + total++;
> + }
> +
> + if (reclaimed)
> + *reclaimed = total;
> +
> + return ret;
> +}
> +
> static void *zs_zpool_map(void *pool, unsigned long handle,
> enum zpool_mapmode mm)
> {
> @@ -463,6 +483,7 @@ static struct zpool_driver zs_zpool_driver = {
> .malloc_support_movable = true,
> .malloc = zs_zpool_malloc,
> .free = zs_zpool_free,
> + .shrink = zs_zpool_shrink,
> .map = zs_zpool_map,
> .unmap = zs_zpool_unmap,
> .total_size = zs_zpool_total_size,
> @@ -936,6 +957,23 @@ static int trylock_zspage(struct zspage *zspage)
> return 0;
> }
>
> +#ifdef CONFIG_ZPOOL
> +/*
> + * Free all the deferred handles whose objects are freed in zs_free.
> + */
> +static void free_handles(struct zs_pool *pool, struct zspage *zspage)
> +{
> + unsigned long handle = (unsigned long)zspage->deferred_handles;
> +
> + while (handle) {
> + unsigned long nxt_handle = handle_to_obj(handle);
> +
> + cache_free_handle(pool, handle);
> + handle = nxt_handle;
> + }
> +}
# else
static inline void free_handles(struct zs_pool *pool, struct zspage *zspage) {}
> +#endif
> +
> static void __free_zspage(struct zs_pool *pool, struct size_class *class,
> struct zspage *zspage)
> {
> @@ -950,6 +988,11 @@ static void __free_zspage(struct zs_pool *pool, struct size_class *class,
> VM_BUG_ON(get_zspage_inuse(zspage));
> VM_BUG_ON(fg != ZS_EMPTY);
>
> +#ifdef CONFIG_ZPOOL
Let's remove the ifdef machinery here.
> + /* Free all deferred handles from zs_free */
> + free_handles(pool, zspage);
> +#endif
> +
Other than that, looks good to me.
