The patch titled
Subject: mm: remove code to handle same filled pages
has been added to the -mm mm-unstable branch. Its filename is
mm-remove-code-to-handle-same-filled-pages.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-remove-code-to-handle-same-filled-pages.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Usama Arif <usamaarif642@xxxxxxxxx>
Subject: mm: remove code to handle same filled pages
Date: Fri, 23 Aug 2024 20:04:40 +0100
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.
Link: https://lkml.kernel.org/r/20240823190545.979059-3-usamaarif642@xxxxxxxxx
Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
Reviewed-by: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Acked-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zswap.c | 85 ++++-----------------------------------------------
1 file changed, 8 insertions(+), 77 deletions(-)
--- a/mm/zswap.c~mm-remove-code-to-handle-same-filled-pages
+++ a/mm/zswap.c
@@ -44,8 +44,6 @@
**********************************/
/* The number of compressed pages currently stored in zswap */
atomic_t zswap_stored_pages = ATOMIC_INIT(0);
-/* The number of same-value filled pages currently stored in zswap */
-static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
/*
* 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 both
- * pool and lru are invalid and must be ignored.
+ * decompression.
* referenced - true if the entry recently entered the zswap pool. Unset by the
* writeback logic. The entry is only reclaimed by the writeback
* 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(struc
*/
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_coun
* 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);
}
@@ -1417,42 +1402,6 @@ resched:
}
/*********************************
-* 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 = PAGE_SIZE / sizeof(*data) - 1;
- bool ret = false;
-
- data = kmap_local_folio(folio, 0);
- val = data[0];
-
- if (val != data[last_pos])
- goto out;
-
- for (pos = 1; pos < last_pos; pos++) {
- if (val != data[pos])
- goto out;
- }
-
- *value = val;
- ret = true;
-out:
- kunmap_local(data);
- return ret;
-}
-
-static void zswap_fill_folio(struct folio *folio, unsigned long value)
-{
- unsigned long *data = kmap_local_folio(folio, 0);
-
- memset_l(data, value, PAGE_SIZE / sizeof(unsigned long));
- kunmap_local(data);
-}
-
-/*********************************
* main API
**********************************/
bool zswap_store(struct folio *folio)
@@ -1463,7 +1412,6 @@ bool zswap_store(struct folio *folio)
struct zswap_entry *entry, *old;
struct obj_cgroup *objcg = NULL;
struct mem_cgroup *memcg = NULL;
- unsigned long value;
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;
}
- if (zswap_is_folio_same_filled(folio, &value)) {
- entry->length = 0;
- entry->value = value;
- atomic_inc(&zswap_same_filled_pages);
- goto store_entry;
- }
-
/* if entry is successfully added, it keeps the reference */
entry->pool = 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;
-store_entry:
entry->swpentry = swp;
entry->objcg = objcg;
entry->referenced = true;
@@ -1569,13 +1509,9 @@ store_entry:
return true;
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;
- if (entry->length)
- zswap_decompress(entry, folio);
- else
- zswap_fill_folio(folio, entry->value);
+ zswap_decompress(entry, folio);
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);
return 0;
}
_
Patches currently in -mm which might be from usamaarif642@xxxxxxxxx are
revert-mm-skip-cma-pages-when-they-are-not-available.patch
revert-mm-skip-cma-pages-when-they-are-not-available-update.patch
mm-store-zero-pages-to-be-swapped-out-in-a-bitmap.patch
mm-remove-code-to-handle-same-filled-pages.patch
