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[2a03:2880:20ff:12::face:b00c]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6c162d4c1c6sm21607346d6.46.2024.08.23.12.05.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Aug 2024 12:05:48 -0700 (PDT) From: Usama Arif To: akpm@linux-foundation.org Cc: hannes@cmpxchg.org, shakeel.butt@linux.dev, david@redhat.com, ying.huang@intel.com, hughd@google.com, willy@infradead.org, yosryahmed@google.com, nphamcs@gmail.com, chengming.zhou@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Usama Arif , Andi Kleen Subject: [RESEND v8 2/2] mm: remove code to handle same filled pages Date: Fri, 23 Aug 2024 20:04:40 +0100 Message-ID: <20240823190545.979059-3-usamaarif642@gmail.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20240823190545.979059-1-usamaarif642@gmail.com> References: <20240823190545.979059-1-usamaarif642@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" With an earlier commit to handle zero-filled pages in swap directly, and with only 1% of the same-filled pages being non-zero, zswap no longer needs to handle same-filled pages and can just work on compressed pages. Reviewed-by: Chengming Zhou Acked-by: Yosry Ahmed Reviewed-by: Nhat Pham Cc: Andi Kleen Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Shakeel Butt Signed-off-by: Andrew Morton Acked-by: Johannes Weiner Signed-off-by: Usama Arif --- mm/zswap.c | 85 +++++------------------------------------------------- 1 file changed, 8 insertions(+), 77 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index df66ab102d27..449914ea9919 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -44,8 +44,6 @@ **********************************/ /* The number of compressed pages currently stored in zswap */ atomic_t zswap_stored_pages =3D ATOMIC_INIT(0); -/* The number of same-value filled pages currently stored in zswap */ -static atomic_t zswap_same_filled_pages =3D ATOMIC_INIT(0); =20 /* * The statistics below are not protected from concurrent access for @@ -185,8 +183,7 @@ static struct shrinker *zswap_shrinker; * * swpentry - associated swap entry, the offset indexes into the red-black= tree * length - the length in bytes of the compressed page data. Needed during - * decompression. For a same value filled page length is 0, and b= oth - * pool and lru are invalid and must be ignored. + * decompression. * referenced - true if the entry recently entered the zswap pool. Unset b= y the * writeback logic. The entry is only reclaimed by the writeb= ack * logic if referenced is unset. See comments in the shrinker @@ -202,10 +199,7 @@ struct zswap_entry { unsigned int length; bool referenced; struct zswap_pool *pool; - union { - unsigned long handle; - unsigned long value; - }; + unsigned long handle; struct obj_cgroup *objcg; struct list_head lru; }; @@ -801,13 +795,9 @@ static void zswap_entry_cache_free(struct zswap_entry = *entry) */ static void zswap_entry_free(struct zswap_entry *entry) { - if (!entry->length) - atomic_dec(&zswap_same_filled_pages); - else { - zswap_lru_del(&zswap_list_lru, entry); - zpool_free(entry->pool->zpool, entry->handle); - zswap_pool_put(entry->pool); - } + zswap_lru_del(&zswap_list_lru, entry); + zpool_free(entry->pool->zpool, entry->handle); + zswap_pool_put(entry->pool); if (entry->objcg) { obj_cgroup_uncharge_zswap(entry->objcg, entry->length); obj_cgroup_put(entry->objcg); @@ -1277,11 +1267,6 @@ static unsigned long zswap_shrinker_count(struct shr= inker *shrinker, * This ensures that the better zswap compresses memory, the fewer * pages we will evict to swap (as it will otherwise incur IO for * relatively small memory saving). - * - * The memory saving factor calculated here takes same-filled pages into - * account, but those are not freeable since they almost occupy no - * space. Hence, we may scale nr_freeable down a little bit more than we - * should if we have a lot of same-filled pages. */ return mult_frac(nr_freeable, nr_backing, nr_stored); } @@ -1416,42 +1401,6 @@ static void shrink_worker(struct work_struct *w) } while (zswap_total_pages() > thr); } =20 -/********************************* -* same-filled functions -**********************************/ -static bool zswap_is_folio_same_filled(struct folio *folio, unsigned long = *value) -{ - unsigned long *data; - unsigned long val; - unsigned int pos, last_pos =3D PAGE_SIZE / sizeof(*data) - 1; - bool ret =3D false; - - data =3D kmap_local_folio(folio, 0); - val =3D data[0]; - - if (val !=3D data[last_pos]) - goto out; - - for (pos =3D 1; pos < last_pos; pos++) { - if (val !=3D data[pos]) - goto out; - } - - *value =3D val; - ret =3D true; -out: - kunmap_local(data); - return ret; -} - -static void zswap_fill_folio(struct folio *folio, unsigned long value) -{ - unsigned long *data =3D kmap_local_folio(folio, 0); - - memset_l(data, value, PAGE_SIZE / sizeof(unsigned long)); - kunmap_local(data); -} - /********************************* * main API **********************************/ @@ -1463,7 +1412,6 @@ bool zswap_store(struct folio *folio) struct zswap_entry *entry, *old; struct obj_cgroup *objcg =3D NULL; struct mem_cgroup *memcg =3D NULL; - unsigned long value; =20 VM_WARN_ON_ONCE(!folio_test_locked(folio)); VM_WARN_ON_ONCE(!folio_test_swapcache(folio)); @@ -1496,13 +1444,6 @@ bool zswap_store(struct folio *folio) goto reject; } =20 - if (zswap_is_folio_same_filled(folio, &value)) { - entry->length =3D 0; - entry->value =3D value; - atomic_inc(&zswap_same_filled_pages); - goto store_entry; - } - /* if entry is successfully added, it keeps the reference */ entry->pool =3D zswap_pool_current_get(); if (!entry->pool) @@ -1520,7 +1461,6 @@ bool zswap_store(struct folio *folio) if (!zswap_compress(folio, entry)) goto put_pool; =20 -store_entry: entry->swpentry =3D swp; entry->objcg =3D objcg; entry->referenced =3D true; @@ -1569,13 +1509,9 @@ bool zswap_store(struct folio *folio) return true; =20 store_failed: - if (!entry->length) - atomic_dec(&zswap_same_filled_pages); - else { - zpool_free(entry->pool->zpool, entry->handle); + zpool_free(entry->pool->zpool, entry->handle); put_pool: - zswap_pool_put(entry->pool); - } + zswap_pool_put(entry->pool); freepage: zswap_entry_cache_free(entry); reject: @@ -1638,10 +1574,7 @@ bool zswap_load(struct folio *folio) if (!entry) return false; =20 - if (entry->length) - zswap_decompress(entry, folio); - else - zswap_fill_folio(folio, entry->value); + zswap_decompress(entry, folio); =20 count_vm_event(ZSWPIN); if (entry->objcg) @@ -1744,8 +1677,6 @@ static int zswap_debugfs_init(void) zswap_debugfs_root, NULL, &total_size_fops); debugfs_create_atomic_t("stored_pages", 0444, zswap_debugfs_root, &zswap_stored_pages); - debugfs_create_atomic_t("same_filled_pages", 0444, - zswap_debugfs_root, &zswap_same_filled_pages); =20 return 0; } --=20 2.43.5