[PATCH v3 11/13] mm: zswap: Allocate acomp_batch_ctx resources for a given zswap_pool.

Kanchana P Sridhar
2024-11-06T19:21:15Z

If the zswap_pool is associated with an acomp_alg/crypto_acomp that has
registered batch_compress() and batch_decompress() API, we can allocate the
necessary batching resources for the pool's acomp_batch_ctx.

This patch makes the above determination on incurring the per-cpu memory
footprint cost for batching, and if so, goes ahead and allocates
SWAP_CRYPTO_BATCH_SIZE (i.e. 8) acomp_reqs/buffers for the
pool->acomp_batch_ctx on that specific cpu.

It also "remembers" the pool's batching readiness as a result of the above,
through a new

enum batch_comp_status can_batch_comp;

member added to struct zswap_pool, for fast retrieval during
zswap_store().

This allows us a way to only incur the memory footprint cost of the
pool->acomp_batch_ctx resources for a given cpu on which zswap_store()
needs to process a large folio.

Suggested-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Ying Huang <ying.huang@intel.com>
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
---
include/linux/zswap.h | 7 ++++++
mm/zswap.c | 52 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 59 insertions(+)

diff --git a/include/linux/zswap.h b/include/linux/zswap.h
index d961ead91bf1..9ad27ab3d222 100644
--- a/include/linux/zswap.h
+++ b/include/linux/zswap.h
@@ -7,6 +7,13 @@

struct lruvec;

+/*
+ * For IAA compression batching:
+ * Maximum number of IAA acomp compress requests that will be processed
+ * in a batch: in parallel, if iaa_crypto async/no irq mode is enabled
+ * (the default); else sequentially, if iaa_crypto sync mode is in effect.
+ */
+#define SWAP_CRYPTO_BATCH_SIZE 8UL
extern atomic_long_t zswap_stored_pages;

#ifdef CONFIG_ZSWAP
diff --git a/mm/zswap.c b/mm/zswap.c
index 80a928cf0f7e..2af736e38213 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -151,6 +151,12 @@ struct crypto_acomp_ctx {
bool is_sleepable;
};

+enum batch_comp_status {
+ UNINIT_BATCH_COMP = -1,
+ CANNOT_BATCH_COMP = 0,
+ BATCH_COMP_ENABLED = 1,
+};
+
/*
* The lock ordering is zswap_tree.lock -> zswap_pool.lru_lock.
* The only case where lru_lock is not acquired while holding tree.lock is
@@ -159,6 +165,7 @@ struct crypto_acomp_ctx {
*/
struct zswap_pool {
struct zpool *zpool;
+ enum batch_comp_status can_batch_comp;
struct crypto_acomp_ctx __percpu *acomp_ctx;
struct crypto_acomp_ctx __percpu *acomp_batch_ctx;
struct percpu_ref ref;
@@ -310,6 +317,7 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
goto ref_fail;
INIT_LIST_HEAD(&pool->list);

+ pool->can_batch_comp = UNINIT_BATCH_COMP;
zswap_pool_debug("created", pool);

return pool;
@@ -695,6 +703,39 @@ static int zswap_enabled_param_set(const char *val,
return ret;
}

+/* Called only if sysctl vm.compress-batching is set to "1". */
+static __always_inline bool zswap_pool_can_batch(struct zswap_pool *pool)
+{
+ struct crypto_acomp_ctx *acomp_ctx;
+
+ if ((pool->can_batch_comp == BATCH_COMP_ENABLED) &&
+ !IS_ERR_OR_NULL((acomp_ctx = raw_cpu_ptr(pool->acomp_batch_ctx))) &&
+ (acomp_ctx->nr_reqs == SWAP_CRYPTO_BATCH_SIZE))
+ return true;
+
+ if (pool->can_batch_comp == CANNOT_BATCH_COMP)
+ return false;
+
+ if ((pool->can_batch_comp == UNINIT_BATCH_COMP) && pool->acomp_batch_ctx) {
+ acomp_ctx = raw_cpu_ptr(pool->acomp_batch_ctx);
+
+ if (!IS_ERR_OR_NULL(acomp_ctx)) {
+ if ((acomp_ctx->nr_reqs == SWAP_CRYPTO_BATCH_SIZE) ||
+ (!acomp_ctx->nr_reqs &&
+ !zswap_create_acomp_ctx(raw_smp_processor_id(),
+ acomp_ctx,
+ pool->tfm_name,
+ SWAP_CRYPTO_BATCH_SIZE))) {
+ pool->can_batch_comp = BATCH_COMP_ENABLED;
+ return true;
+ }
+ }
+ }
+
+ pool->can_batch_comp = CANNOT_BATCH_COMP;
+ return false;
+}
+
/*********************************
* lru functions
**********************************/
@@ -850,6 +891,17 @@ static int zswap_create_acomp_ctx(unsigned int cpu,
acomp_ctx->acomp = acomp;
acomp_ctx->is_sleepable = acomp_is_async(acomp);

+ /*
+ * Cannot create a batching ctx without the crypto acomp alg supporting
+ * batch_compress and batch_decompress API.
+ */
+ if ((nr_reqs > 1) && (!acomp->batch_compress || !acomp->batch_decompress)) {
+ WARN_ONCE(1, "Cannot alloc acomp_ctx with %d reqs since crypto acomp %s\nhas not registered batch_compress() and/or batch_decompress()\n",
+ nr_reqs, tfm_name);
+ ret = -ENODEV;
+ goto buf_fail;
+ }
+
acomp_ctx->buffers = kmalloc_node(nr_reqs * sizeof(u8 *),
GFP_KERNEL, cpu_to_node(cpu));
if (!acomp_ctx->buffers)
--
2.27.0