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authorBarry Song <v-songbaohua@oppo.com>2024-02-22 21:11:35 +1300
committerAndrew Morton <akpm@linux-foundation.org>2024-03-13 12:12:21 -0700
commit270700dd06ca41a4779c19eb46608f076bb7d40e (patch)
treead613329adff0fd5c2f85e47f5c21273b9bced26
parent6c303f1af356f5f6847146ab0199dc3fe61d8f46 (diff)
mm/zswap: remove the memcpy if acomp is not sleepable
Most compressors are actually CPU-based and won't sleep during compression and decompression. We should remove the redundant memcpy for them. This patch checks if the algorithm is sleepable by testing the CRYPTO_ALG_ASYNC algorithm flag. Generally speaking, async and sleepable are semantically similar but not equal. But for compress drivers, they are basically equal at least due to the below facts. Firstly, scompress drivers - crypto/deflate.c, lz4.c, zstd.c, lzo.c etc have no sleep. Secondly, zRAM has been using these scompress drivers for years in atomic contexts, and never worried those drivers going to sleep. One exception is that an async driver can sometimes still return synchronously per Herbert's clarification. In this case, we are still having a redundant memcpy. But we can't know if one particular acomp request will sleep or not unless crypto can expose more details for each specific request from offload drivers. Link: https://lkml.kernel.org/r/20240222081135.173040-3-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Tested-by: Chengming Zhou <zhouchengming@bytedance.com> Reviewed-by: Nhat Pham <nphamcs@gmail.com> Acked-by: Yosry Ahmed <yosryahmed@google.com> Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com> Acked-by: Chris Li <chrisl@kernel.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Dan Streetman <ddstreet@ieee.org> Cc: David S. Miller <davem@davemloft.net> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Seth Jennings <sjenning@redhat.com> Cc: Vitaly Wool <vitaly.wool@konsulko.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--mm/zswap.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/zswap.c b/mm/zswap.c
index 9a3237752082..9dec853647c8 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -162,6 +162,7 @@ struct crypto_acomp_ctx {
struct crypto_wait wait;
u8 *buffer;
struct mutex mutex;
+ bool is_sleepable;
};
/*
@@ -951,6 +952,7 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
goto acomp_fail;
}
acomp_ctx->acomp = acomp;
+ acomp_ctx->is_sleepable = acomp_is_async(acomp);
req = acomp_request_alloc(acomp_ctx->acomp);
if (!req) {
@@ -1078,7 +1080,7 @@ static void zswap_decompress(struct zswap_entry *entry, struct page *page)
mutex_lock(&acomp_ctx->mutex);
src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
- if (!zpool_can_sleep_mapped(zpool)) {
+ if (acomp_ctx->is_sleepable && !zpool_can_sleep_mapped(zpool)) {
memcpy(acomp_ctx->buffer, src, entry->length);
src = acomp_ctx->buffer;
zpool_unmap_handle(zpool, entry->handle);
@@ -1092,7 +1094,7 @@ static void zswap_decompress(struct zswap_entry *entry, struct page *page)
BUG_ON(acomp_ctx->req->dlen != PAGE_SIZE);
mutex_unlock(&acomp_ctx->mutex);
- if (zpool_can_sleep_mapped(zpool))
+ if (!acomp_ctx->is_sleepable || zpool_can_sleep_mapped(zpool))
zpool_unmap_handle(zpool, entry->handle);
}