This patch sets up zswap for allocating per-CPU resources optimally for non-batching and batching compressors. A new ZSWAP_MAX_BATCH_SIZE constant is defined as 8U, to set an upper limit on the number of pages in large folios that will be batch compressed. As per Herbert's comments in [2] in response to the crypto_acomp_batch_compress() and crypto_acomp_batch_decompress() API proposed in [1], this series does not create new crypto_acomp batching API. Instead, zswap compression batching uses the existing crypto_acomp_compress() API in combination with the "void *kernel_data" member added to "struct acomp_req" earlier in this series. It is up to the compressor to manage multiple requests, as needed, to accomplish batch parallelism. zswap only needs to allocate the per-CPU dst buffers according to the batch size supported by the compressor. A "u8 compr_batch_size" member is added to "struct zswap_pool", as per Yosry's suggestion. pool->compr_batch_size is set as the minimum of the compressor's max batch-size and ZSWAP_MAX_BATCH_SIZE. Accordingly, it proceeds to allocate the necessary compression dst buffers in the per-CPU acomp_ctx. Another "u8 batch_size" member is added to "struct zswap_pool" to store the unit for batching large folio stores: for batching compressors, this is the pool->compr_batch_size. For non-batching compressors, this is ZSWAP_MAX_BATCH_SIZE. zswap does not use more than one dst buffer yet. Follow-up patches will actually utilize the multiple acomp_ctx buffers for batch compression/decompression of multiple pages. Thus, ZSWAP_MAX_BATCH_SIZE limits the amount of extra memory used for batching. There is a small extra memory overhead of allocating the acomp_ctx->buffers array for compressors that do not support batching: On x86_64, the overhead is 1 pointer per-CPU (i.e. 8 bytes). [1]: https://patchwork.kernel.org/project/linux-mm/patch/20250508194134.28392-11-kanchana.p.sridhar@xxxxxxxxx/ [2]: https://patchwork.kernel.org/comment/26382610 Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx> --- mm/zswap.c | 82 +++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 63 insertions(+), 19 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index efd501a7fe294..63a997b999537 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -80,6 +80,9 @@ static bool zswap_pool_reached_full; #define ZSWAP_PARAM_UNSET "" +/* Limit the batch size to limit per-CPU memory usage for dst buffers. */ +#define ZSWAP_MAX_BATCH_SIZE 8U + static int zswap_setup(void); /* Enable/disable zswap */ @@ -147,7 +150,7 @@ struct crypto_acomp_ctx { struct crypto_acomp *acomp; struct acomp_req *req; struct crypto_wait wait; - u8 *buffer; + u8 **buffers; struct mutex mutex; bool is_sleepable; }; @@ -166,6 +169,8 @@ struct zswap_pool { struct work_struct release_work; struct hlist_node node; char tfm_name[CRYPTO_MAX_ALG_NAME]; + u8 compr_batch_size; + u8 batch_size; }; /* Global LRU lists shared by all zswap pools. */ @@ -258,8 +263,10 @@ static void __zswap_pool_empty(struct percpu_ref *ref); * zswap_cpu_comp_prepare(), not others. * - Cleanup acomp_ctx resources on all cores in zswap_pool_destroy(). */ -static void acomp_ctx_dealloc(struct crypto_acomp_ctx *acomp_ctx) +static void acomp_ctx_dealloc(struct crypto_acomp_ctx *acomp_ctx, u8 nr_buffers) { + u8 i; + if (IS_ERR_OR_NULL(acomp_ctx)) return; @@ -269,7 +276,11 @@ static void acomp_ctx_dealloc(struct crypto_acomp_ctx *acomp_ctx) if (!IS_ERR_OR_NULL(acomp_ctx->acomp)) crypto_free_acomp(acomp_ctx->acomp); - kfree(acomp_ctx->buffer); + if (acomp_ctx->buffers) { + for (i = 0; i < nr_buffers; ++i) + kfree(acomp_ctx->buffers[i]); + kfree(acomp_ctx->buffers); + } } static struct zswap_pool *zswap_pool_create(char *type, char *compressor) @@ -290,6 +301,7 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor) return NULL; } + /* Many things rely on the zero-initialization. */ pool = kzalloc(sizeof(*pool), GFP_KERNEL); if (!pool) return NULL; @@ -352,13 +364,28 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor) goto ref_fail; INIT_LIST_HEAD(&pool->list); + /* + * Set the unit of compress batching for large folios, for quick + * retrieval in the zswap_compress() fast path: + * If the compressor is sequential (@pool->compr_batch_size is 1), + * large folios will be compressed in batches of ZSWAP_MAX_BATCH_SIZE + * pages, where each page in the batch is compressed sequentially. + * We see better performance by processing the folio in batches of + * ZSWAP_MAX_BATCH_SIZE, due to cache locality of working set + * structures. + */ + pool->batch_size = (pool->compr_batch_size > 1) ? + pool->compr_batch_size : ZSWAP_MAX_BATCH_SIZE; + zswap_pool_debug("created", pool); return pool; ref_fail: for_each_possible_cpu(cpu) - acomp_ctx_dealloc(per_cpu_ptr(pool->acomp_ctx, cpu)); + acomp_ctx_dealloc(per_cpu_ptr(pool->acomp_ctx, cpu), + pool->compr_batch_size); + error: if (pool->acomp_ctx) free_percpu(pool->acomp_ctx); @@ -417,7 +444,8 @@ static void zswap_pool_destroy(struct zswap_pool *pool) zswap_pool_debug("destroying", pool); for_each_possible_cpu(cpu) - acomp_ctx_dealloc(per_cpu_ptr(pool->acomp_ctx, cpu)); + acomp_ctx_dealloc(per_cpu_ptr(pool->acomp_ctx, cpu), + pool->compr_batch_size); free_percpu(pool->acomp_ctx); @@ -876,6 +904,7 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu); int ret = -ENOMEM; + u8 i; /* * The per-CPU pool->acomp_ctx is zero-initialized on allocation. @@ -888,10 +917,6 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) if (!IS_ERR_OR_NULL(acomp_ctx->acomp)) return 0; - acomp_ctx->buffer = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu)); - if (!acomp_ctx->buffer) - return ret; - acomp_ctx->acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu)); if (IS_ERR_OR_NULL(acomp_ctx->acomp)) { pr_err("could not alloc crypto acomp %s : %ld\n", @@ -904,17 +929,36 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) acomp_ctx->req = acomp_request_alloc(acomp_ctx->acomp); if (IS_ERR_OR_NULL(acomp_ctx->req)) { pr_err("could not alloc crypto acomp_request %s\n", - pool->tfm_name); + pool->tfm_name); goto fail; } - crypto_init_wait(&acomp_ctx->wait); + /* + * Allocate up to ZSWAP_MAX_BATCH_SIZE dst buffers if the + * compressor supports batching. + */ + pool->compr_batch_size = min(ZSWAP_MAX_BATCH_SIZE, + crypto_acomp_batch_size(acomp_ctx->acomp)); + + acomp_ctx->buffers = kcalloc_node(pool->compr_batch_size, sizeof(u8 *), + GFP_KERNEL, cpu_to_node(cpu)); + if (!acomp_ctx->buffers) + goto fail; + + for (i = 0; i < pool->compr_batch_size; ++i) { + acomp_ctx->buffers[i] = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, + cpu_to_node(cpu)); + if (!acomp_ctx->buffers[i]) + goto fail; + } /* * if the backend of acomp is async zip, crypto_req_done() will wakeup * crypto_wait_req(); if the backend of acomp is scomp, the callback * won't be called, crypto_wait_req() will return without blocking. */ + crypto_init_wait(&acomp_ctx->wait); + acomp_request_set_callback(acomp_ctx->req, CRYPTO_TFM_REQ_MAY_BACKLOG, crypto_req_done, &acomp_ctx->wait); @@ -922,7 +966,7 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) return 0; fail: - acomp_ctx_dealloc(acomp_ctx); + acomp_ctx_dealloc(acomp_ctx, pool->compr_batch_size); return ret; } @@ -942,7 +986,7 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry, mutex_lock(&acomp_ctx->mutex); - dst = acomp_ctx->buffer; + dst = acomp_ctx->buffers[0]; sg_init_table(&input, 1); sg_set_page(&input, page, PAGE_SIZE, 0); @@ -1003,19 +1047,19 @@ static bool zswap_decompress(struct zswap_entry *entry, struct folio *folio) acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx); mutex_lock(&acomp_ctx->mutex); - obj = zpool_obj_read_begin(zpool, entry->handle, acomp_ctx->buffer); + obj = zpool_obj_read_begin(zpool, entry->handle, acomp_ctx->buffers[0]); /* * zpool_obj_read_begin() might return a kmap address of highmem when - * acomp_ctx->buffer is not used. However, sg_init_one() does not - * handle highmem addresses, so copy the object to acomp_ctx->buffer. + * acomp_ctx->buffers[0] is not used. However, sg_init_one() does not + * handle highmem addresses, so copy the object to acomp_ctx->buffers[0]. */ if (virt_addr_valid(obj)) { src = obj; } else { - WARN_ON_ONCE(obj == acomp_ctx->buffer); - memcpy(acomp_ctx->buffer, obj, entry->length); - src = acomp_ctx->buffer; + WARN_ON_ONCE(obj == acomp_ctx->buffers[0]); + memcpy(acomp_ctx->buffers[0], obj, entry->length); + src = acomp_ctx->buffers[0]; } sg_init_one(&input, src, entry->length); -- 2.27.0
