The patch titled
Subject: mm/zswap: reuse dstmem when decompress
has been added to the -mm mm-unstable branch. Its filename is
mm-zswap-reuse-dstmem-when-decompress.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-reuse-dstmem-when-decompress.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: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Subject: mm/zswap: reuse dstmem when decompress
Date: Wed, 13 Dec 2023 04:17:58 +0000
Patch series "mm/zswap: dstmem reuse optimizations and cleanups".
The problem this series tries to optimize is that zswap_load() and
zswap_writeback_entry() have to malloc a temporary memory to support
!zpool_can_sleep_mapped(). We can avoid it by reusing the percpu
crypto_acomp_ctx->dstmem, which is also used by zswap_store() and
protected by the same percpu crypto_acomp_ctx->mutex.
This patch (of 5):
In the !zpool_can_sleep_mapped() case such as zsmalloc, we need to first
copy the entry->handle memory to a temporary memory, which is allocated
using kmalloc.
Obviously we can reuse the per-compressor dstmem to avoid allocating every
time, since it's percpu-compressor and protected in mutex.
Link: https://lkml.kernel.org/r/20231213-zswap-dstmem-v1-0-896763369d04@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20231213-zswap-dstmem-v1-1-896763369d04@xxxxxxxxxxxxx
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Chris Li <chriscli@xxxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxx>
Cc: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zswap.c | 29 +++++++++--------------------
1 file changed, 9 insertions(+), 20 deletions(-)
--- a/mm/zswap.c~mm-zswap-reuse-dstmem-when-decompress
+++ a/mm/zswap.c
@@ -1767,9 +1767,9 @@ bool zswap_load(struct folio *folio)
struct zswap_entry *entry;
struct scatterlist input, output;
struct crypto_acomp_ctx *acomp_ctx;
- u8 *src, *dst, *tmp;
+ unsigned int dlen = PAGE_SIZE;
+ u8 *src, *dst;
struct zpool *zpool;
- unsigned int dlen;
bool ret;
VM_WARN_ON_ONCE(!folio_test_locked(folio));
@@ -1791,27 +1791,18 @@ bool zswap_load(struct folio *folio)
goto stats;
}
- zpool = zswap_find_zpool(entry);
- if (!zpool_can_sleep_mapped(zpool)) {
- tmp = kmalloc(entry->length, GFP_KERNEL);
- if (!tmp) {
- ret = false;
- goto freeentry;
- }
- }
-
/* decompress */
- dlen = PAGE_SIZE;
- src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
+ acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
+ mutex_lock(acomp_ctx->mutex);
+ zpool = zswap_find_zpool(entry);
+ src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
if (!zpool_can_sleep_mapped(zpool)) {
- memcpy(tmp, src, entry->length);
- src = tmp;
+ memcpy(acomp_ctx->dstmem, src, entry->length);
+ src = acomp_ctx->dstmem;
zpool_unmap_handle(zpool, entry->handle);
}
- acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
- mutex_lock(acomp_ctx->mutex);
sg_init_one(&input, src, entry->length);
sg_init_table(&output, 1);
sg_set_page(&output, page, PAGE_SIZE, 0);
@@ -1822,15 +1813,13 @@ bool zswap_load(struct folio *folio)
if (zpool_can_sleep_mapped(zpool))
zpool_unmap_handle(zpool, entry->handle);
- else
- kfree(tmp);
ret = true;
stats:
count_vm_event(ZSWPIN);
if (entry->objcg)
count_objcg_event(entry->objcg, ZSWPIN);
-freeentry:
+
spin_lock(&tree->lock);
if (ret && zswap_exclusive_loads_enabled) {
zswap_invalidate_entry(tree, entry);
_
Patches currently in -mm which might be from zhouchengming@xxxxxxxxxxxxx are
mm-zswap-reuse-dstmem-when-decompress.patch
mm-zswap-change-dstmem-size-to-one-page.patch
mm-zswap-refactor-out-__zswap_load.patch
mm-zswap-cleanup-zswap_load.patch
mm-zswap-cleanup-zswap_reclaim_entry.patch
