From: Vitaly Wool <vitaly.wool@konsulko.com>
To: Nhat Pham <nphamcs@gmail.com>
Cc: akpm@linux-foundation.org, hannes@cmpxchg.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
minchan@kernel.org, ngupta@vflare.org, senozhatsky@chromium.org,
sjenning@redhat.com, ddstreet@ieee.org
Subject: Re: [PATCH v7 4/6] zsmalloc: Add a LRU to zs_pool to keep track of zspages in LRU order
Date: Tue, 29 Nov 2022 12:53:30 +0100 [thread overview]
Message-ID: <CAM4kBB+7boz+PZfPODbS-KMGOPZpa2QO5xZMoP2q_ZfGyqmQTA@mail.gmail.com> (raw)
In-Reply-To: <20221128191616.1261026-5-nphamcs@gmail.com>
On Mon, Nov 28, 2022 at 8:16 PM Nhat Pham <nphamcs@gmail.com> wrote:
>
> This helps determines the coldest zspages as candidates for writeback.
>
> Signed-off-by: Nhat Pham <nphamcs@gmail.com>
> ---
> mm/zsmalloc.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 5427a00a0518..b1bc231d94a3 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -239,6 +239,11 @@ struct zs_pool {
> /* Compact classes */
> struct shrinker shrinker;
>
> +#ifdef CONFIG_ZPOOL
> + /* List tracking the zspages in LRU order by most recently added object */
> + struct list_head lru;
> +#endif
> +
> #ifdef CONFIG_ZSMALLOC_STAT
> struct dentry *stat_dentry;
> #endif
> @@ -260,6 +265,12 @@ struct zspage {
> unsigned int freeobj;
> struct page *first_page;
> struct list_head list; /* fullness list */
> +
> +#ifdef CONFIG_ZPOOL
> + /* links the zspage to the lru list in the pool */
> + struct list_head lru;
> +#endif
> +
> struct zs_pool *pool;
> #ifdef CONFIG_COMPACTION
> rwlock_t lock;
> @@ -953,6 +964,9 @@ static void free_zspage(struct zs_pool *pool, struct size_class *class,
> }
>
> remove_zspage(class, zspage, ZS_EMPTY);
> +#ifdef CONFIG_ZPOOL
> + list_del(&zspage->lru);
> +#endif
> __free_zspage(pool, class, zspage);
> }
>
> @@ -998,6 +1012,10 @@ static void init_zspage(struct size_class *class, struct zspage *zspage)
> off %= PAGE_SIZE;
> }
>
> +#ifdef CONFIG_ZPOOL
> + INIT_LIST_HEAD(&zspage->lru);
> +#endif
> +
> set_freeobj(zspage, 0);
> }
>
> @@ -1270,6 +1288,31 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
> obj_to_location(obj, &page, &obj_idx);
> zspage = get_zspage(page);
>
> +#ifdef CONFIG_ZPOOL
> + /*
> + * Move the zspage to front of pool's LRU.
> + *
> + * Note that this is swap-specific, so by definition there are no ongoing
> + * accesses to the memory while the page is swapped out that would make
> + * it "hot". A new entry is hot, then ages to the tail until it gets either
> + * written back or swaps back in.
> + *
> + * Furthermore, map is also called during writeback. We must not put an
> + * isolated page on the LRU mid-reclaim.
> + *
> + * As a result, only update the LRU when the page is mapped for write
> + * when it's first instantiated.
> + *
> + * This is a deviation from the other backends, which perform this update
> + * in the allocation function (zbud_alloc, z3fold_alloc).
> + */
> + if (mm == ZS_MM_WO) {
> + if (!list_empty(&zspage->lru))
> + list_del(&zspage->lru);
> + list_add(&zspage->lru, &pool->lru);
> + }
> +#endif
> +
> /*
> * migration cannot move any zpages in this zspage. Here, pool->lock
> * is too heavy since callers would take some time until they calls
> @@ -1988,6 +2031,9 @@ static void async_free_zspage(struct work_struct *work)
> VM_BUG_ON(fullness != ZS_EMPTY);
> class = pool->size_class[class_idx];
> spin_lock(&pool->lock);
> +#ifdef CONFIG_ZPOOL
> + list_del(&zspage->lru);
> +#endif
> __free_zspage(pool, class, zspage);
> spin_unlock(&pool->lock);
> }
> @@ -2299,6 +2345,10 @@ struct zs_pool *zs_create_pool(const char *name)
> */
> zs_register_shrinker(pool);
>
> +#ifdef CONFIG_ZPOOL
> + INIT_LIST_HEAD(&pool->lru);
> +#endif
I think the amount of #ifdefs here becomes absolutely overwhelming.
Not that zsmalloc code was very readable before, but now it is
starting to look like a plain disaster.
Thanks,
Vitaly
> +
> return pool;
>
> err:
> --
> 2.30.2
next prev parent reply other threads:[~2022-11-29 11:53 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-28 19:16 [PATCH v7 0/6] Implement writeback for zsmalloc Nhat Pham
2022-11-28 19:16 ` [PATCH v7 1/6] zswap: fix writeback lock ordering " Nhat Pham
2022-11-29 3:47 ` Sergey Senozhatsky
2022-11-28 19:16 ` [PATCH v7 2/6] zpool: clean out dead code Nhat Pham
2022-11-28 19:16 ` [PATCH v7 3/6] zsmalloc: Consolidate zs_pool's migrate_lock and size_class's locks Nhat Pham
2022-11-29 4:01 ` Sergey Senozhatsky
2022-11-28 19:16 ` [PATCH v7 4/6] zsmalloc: Add a LRU to zs_pool to keep track of zspages in LRU order Nhat Pham
2022-11-28 19:25 ` Johannes Weiner
2022-11-29 3:50 ` Sergey Senozhatsky
2022-11-29 11:53 ` Vitaly Wool [this message]
2022-11-29 14:03 ` Sergey Senozhatsky
2022-11-29 15:54 ` Johannes Weiner
2022-11-30 15:23 ` Vitaly Wool
2022-11-28 19:16 ` [PATCH v7 5/6] zsmalloc: Add zpool_ops field to zs_pool to store evict handlers Nhat Pham
2022-11-28 19:27 ` Johannes Weiner
2022-11-29 3:53 ` Sergey Senozhatsky
2022-11-28 19:16 ` [PATCH v7 6/6] zsmalloc: Implement writeback mechanism for zsmalloc Nhat Pham
2022-11-28 19:28 ` Johannes Weiner
2022-11-29 3:58 ` Sergey Senozhatsky
2023-01-03 4:57 ` [PATCH v7 0/6] Implement writeback " Thomas Weißschuh
2023-01-06 20:32 ` Nhat Pham
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