Message-ID: <B926444035E5E2439431908E3842AFD25A4599@DGGEMI525-MBS.china.huawei.com>
Date:   Thu, 23 Jul 2020 05:41:02 +0000
From:   "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>
To:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Luis Claudio R . Goncalves" <lgoncalv@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Mahipal Challa <mahipalreddy2006@...il.com>,
        Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        Vitaly Wool <vitaly.wool@...sulko.com>,
        "Wangzhou (B)" <wangzhou1@...ilicon.com>,
        "fanghao (A)" <fanghao11@...wei.com>,
        Colin Ian King <colin.king@...onical.com>
CC:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>
Subject: RE: [RESEND PATCH v5] mm/zswap: move to use crypto_acomp API for
 hardware acceleration



> -----Original Message-----
> From: Song Bao Hua (Barry Song)
> Sent: Friday, July 17, 2020 1:51 AM
> To: akpm@...ux-foundation.org; herbert@...dor.apana.org.au;
> davem@...emloft.net
> Cc: linux-crypto@...r.kernel.org; linux-mm@...ck.org;
> linux-kernel@...r.kernel.org; Linuxarm <linuxarm@...wei.com>; Song Bao
> Hua (Barry Song) <song.bao.hua@...ilicon.com>; Luis Claudio R . Goncalves
> <lgoncalv@...hat.com>; Sebastian Andrzej Siewior <bigeasy@...utronix.de>;
> Mahipal Challa <mahipalreddy2006@...il.com>; Seth Jennings
> <sjenning@...hat.com>; Dan Streetman <ddstreet@...e.org>; Vitaly Wool
> <vitaly.wool@...sulko.com>; Wangzhou (B) <wangzhou1@...ilicon.com>;
> fanghao (A) <fanghao11@...wei.com>; Colin Ian King
> <colin.king@...onical.com>
> Subject: [RESEND PATCH v5] mm/zswap: move to use crypto_acomp API for
> hardware acceleration
> 
> Right now, all new ZIP drivers are adapted to crypto_acomp APIs rather than
> legacy crypto_comp APIs. Tradiontal ZIP drivers like lz4,lzo etc have been also
> wrapped into acomp via scomp backend. But zswap.c is still using the old APIs.
> That means zswap won't be able to work on any new ZIP drivers in kernel.
> 
> This patch moves to use cryto_acomp APIs to fix the disconnected bridge
> between new ZIP drivers and zswap. It is probably the first real user to use
> acomp but perhaps not a good example to demonstrate how multiple acomp
> requests can be executed in parallel in one acomp instance.
> frontswap is doing page load and store page by page synchronously.
> swap_writepage() depends on the completion of frontswap_store() to decide if
> it should call __swap_writepage() to swap to disk.
> 
> However this patch creates multiple acomp instances, so multiple threads
> running on multiple different cpus can actually do (de)compression parallelly,
> leveraging the power of multiple ZIP hardware queues. This is also consistent
> with frontswap's page management model.
> 
> The old zswap code uses atomic context and avoids the race conditions while
> shared resources like zswap_dstmem are accessed. Here since acomp can sleep,
> per-cpu mutex is used to replace preemption-disable.
> 
> While it is possible to make mm/page_io.c and mm/frontswap.c support async
> (de)compression in some way, the entire design requires careful thinking and
> performance evaluation. For the first step, the base with fixed connection
> between ZIP drivers and zswap should be built.
> 
> Cc: Luis Claudio R. Goncalves <lgoncalv@...hat.com>
> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Mahipal Challa <mahipalreddy2006@...il.com>
> Cc: Seth Jennings <sjenning@...hat.com>
> Cc: Dan Streetman <ddstreet@...e.org>
> Cc: Vitaly Wool <vitaly.wool@...sulko.com>
> Cc: Zhou Wang <wangzhou1@...ilicon.com>
> Cc: Hao Fang <fanghao11@...wei.com>
> Cc: Colin Ian King <colin.king@...onical.com>
> Signed-off-by: Barry Song <song.bao.hua@...ilicon.com>
> ---
>  v5: address two comments from Sebastian Andrzej Siewior, thanks!
>    1. use pointer rather than pointer's pointer for acomp_ctx;
>    2. fix the race while multiple zpool exist while dynamically switching
>       comprossor and zpool type

Hi All,
Any further comments?

> 
>  mm/zswap.c | 183 ++++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 138 insertions(+), 45 deletions(-)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index fbb782924ccc..8e9c18b6fdd9 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -24,8 +24,10 @@
>  #include <linux/rbtree.h>
>  #include <linux/swap.h>
>  #include <linux/crypto.h>
> +#include <linux/scatterlist.h>
>  #include <linux/mempool.h>
>  #include <linux/zpool.h>
> +#include <crypto/acompress.h>
> 
>  #include <linux/mm_types.h>
>  #include <linux/page-flags.h>
> @@ -127,9 +129,17 @@ module_param_named(same_filled_pages_enabled,
> zswap_same_filled_pages_enabled,
>  * data structures
>  **********************************/
> 
> +struct crypto_acomp_ctx {
> +	struct crypto_acomp *acomp;
> +	struct acomp_req *req;
> +	struct crypto_wait wait;
> +	u8 *dstmem;
> +	struct mutex *mutex;
> +};
> +
>  struct zswap_pool {
>  	struct zpool *zpool;
> -	struct crypto_comp * __percpu *tfm;
> +	struct crypto_acomp_ctx __percpu *acomp_ctx;
>  	struct kref kref;
>  	struct list_head list;
>  	struct work_struct release_work;
> @@ -388,23 +398,43 @@ static struct zswap_entry
> *zswap_entry_find_get(struct rb_root *root,
>  * per-cpu code
>  **********************************/
>  static DEFINE_PER_CPU(u8 *, zswap_dstmem);
> +/*
> + * If users dynamically change the zpool type and compressor at runtime, i.e.
> + * zswap is running, zswap can have more than one zpool on one cpu, but
> +they
> + * are sharing dtsmem. So we need this mutex to be per-cpu.
> + */
> +static DEFINE_PER_CPU(struct mutex *, zswap_mutex);
> 
>  static int zswap_dstmem_prepare(unsigned int cpu)  {
> +	struct mutex *mutex;
>  	u8 *dst;
> 
>  	dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
>  	if (!dst)
>  		return -ENOMEM;
> 
> +	mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu));
> +	if (!mutex) {
> +		kfree(dst);
> +		return -ENOMEM;
> +	}
> +
> +	mutex_init(mutex);
>  	per_cpu(zswap_dstmem, cpu) = dst;
> +	per_cpu(zswap_mutex, cpu) = mutex;
>  	return 0;
>  }
> 
>  static int zswap_dstmem_dead(unsigned int cpu)  {
> +	struct mutex *mutex;
>  	u8 *dst;
> 
> +	mutex = per_cpu(zswap_mutex, cpu);
> +	kfree(mutex);
> +	per_cpu(zswap_mutex, cpu) = NULL;
> +
>  	dst = per_cpu(zswap_dstmem, cpu);
>  	kfree(dst);
>  	per_cpu(zswap_dstmem, cpu) = NULL;
> @@ -415,30 +445,54 @@ static int zswap_dstmem_dead(unsigned int cpu)
> 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_comp *tfm;
> -
> -	if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
> -		return 0;
> +	struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx,
> cpu);
> +	struct crypto_acomp *acomp;
> +	struct acomp_req *req;
> +
> +	acomp = crypto_alloc_acomp(pool->tfm_name, 0, 0);
> +	if (IS_ERR(acomp)) {
> +		pr_err("could not alloc crypto acomp %s : %ld\n",
> +				pool->tfm_name, PTR_ERR(acomp));
> +		return PTR_ERR(acomp);
> +	}
> +	acomp_ctx->acomp = acomp;
> 
> -	tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
> -	if (IS_ERR_OR_NULL(tfm)) {
> -		pr_err("could not alloc crypto comp %s : %ld\n",
> -		       pool->tfm_name, PTR_ERR(tfm));
> +	req = acomp_request_alloc(acomp_ctx->acomp);
> +	if (!req) {
> +		pr_err("could not alloc crypto acomp_request %s\n",
> +		       pool->tfm_name);
> +		crypto_free_acomp(acomp_ctx->acomp);
>  		return -ENOMEM;
>  	}
> -	*per_cpu_ptr(pool->tfm, cpu) = tfm;
> +	acomp_ctx->req = req;
> +
> +	crypto_init_wait(&acomp_ctx->wait);
> +	/*
> +	 * 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.
> +	 */
> +	acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
> +				   crypto_req_done, &acomp_ctx->wait);
> +
> +	acomp_ctx->mutex = per_cpu(zswap_mutex, cpu);
> +	acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu);
> +
>  	return 0;
>  }
> 
>  static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
> {
>  	struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
> -	struct crypto_comp *tfm;
> +	struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx,
> +cpu);
> +
> +	if (!IS_ERR_OR_NULL(acomp_ctx)) {
> +		if (!IS_ERR_OR_NULL(acomp_ctx->req))
> +			acomp_request_free(acomp_ctx->req);
> +		if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
> +			crypto_free_acomp(acomp_ctx->acomp);
> +	}
> 
> -	tfm = *per_cpu_ptr(pool->tfm, cpu);
> -	if (!IS_ERR_OR_NULL(tfm))
> -		crypto_free_comp(tfm);
> -	*per_cpu_ptr(pool->tfm, cpu) = NULL;
>  	return 0;
>  }
> 
> @@ -561,8 +615,9 @@ static struct zswap_pool *zswap_pool_create(char
> *type, char *compressor)
>  	pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
> 
>  	strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
> -	pool->tfm = alloc_percpu(struct crypto_comp *);
> -	if (!pool->tfm) {
> +
> +	pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
> +	if (!pool->acomp_ctx) {
>  		pr_err("percpu alloc failed\n");
>  		goto error;
>  	}
> @@ -585,7 +640,8 @@ static struct zswap_pool *zswap_pool_create(char
> *type, char *compressor)
>  	return pool;
> 
>  error:
> -	free_percpu(pool->tfm);
> +	if (pool->acomp_ctx)
> +		free_percpu(pool->acomp_ctx);
>  	if (pool->zpool)
>  		zpool_destroy_pool(pool->zpool);
>  	kfree(pool);
> @@ -596,14 +652,14 @@ static __init struct zswap_pool
> *__zswap_pool_create_fallback(void)
>  {
>  	bool has_comp, has_zpool;
> 
> -	has_comp = crypto_has_comp(zswap_compressor, 0, 0);
> +	has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
>  	if (!has_comp && strcmp(zswap_compressor,
>  				CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
>  		pr_err("compressor %s not available, using default %s\n",
>  		       zswap_compressor,
> CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
>  		param_free_charp(&zswap_compressor);
>  		zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
> -		has_comp = crypto_has_comp(zswap_compressor, 0, 0);
> +		has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
>  	}
>  	if (!has_comp) {
>  		pr_err("default compressor %s not available\n", @@ -639,7 +695,7
> @@ static void zswap_pool_destroy(struct zswap_pool *pool)
>  	zswap_pool_debug("destroying", pool);
> 
>  	cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
> &pool->node);
> -	free_percpu(pool->tfm);
> +	free_percpu(pool->acomp_ctx);
>  	zpool_destroy_pool(pool->zpool);
>  	kfree(pool);
>  }
> @@ -723,7 +779,7 @@ static int __zswap_param_set(const char *val, const
> struct kernel_param *kp,
>  		}
>  		type = s;
>  	} else if (!compressor) {
> -		if (!crypto_has_comp(s, 0, 0)) {
> +		if (!crypto_has_acomp(s, 0, 0)) {
>  			pr_err("compressor %s not available\n", s);
>  			return -ENOENT;
>  		}
> @@ -774,7 +830,7 @@ static int __zswap_param_set(const char *val, const
> struct kernel_param *kp,
>  		 * failed, maybe both compressor and zpool params were bad.
>  		 * Allow changing this param, so pool creation will succeed
>  		 * when the other param is changed. We already verified this
> -		 * param is ok in the zpool_has_pool() or crypto_has_comp()
> +		 * param is ok in the zpool_has_pool() or crypto_has_acomp()
>  		 * checks above.
>  		 */
>  		ret = param_set_charp(s, kp);
> @@ -876,7 +932,9 @@ static int zswap_writeback_entry(struct zpool *pool,
> unsigned long handle)
>  	pgoff_t offset;
>  	struct zswap_entry *entry;
>  	struct page *page;
> -	struct crypto_comp *tfm;
> +	struct scatterlist input, output;
> +	struct crypto_acomp_ctx *acomp_ctx;
> +
>  	u8 *src, *dst;
>  	unsigned int dlen;
>  	int ret;
> @@ -916,14 +974,21 @@ static int zswap_writeback_entry(struct zpool *pool,
> unsigned long handle)
> 
>  	case ZSWAP_SWAPCACHE_NEW: /* page is locked */
>  		/* decompress */
> +		acomp_ctx = this_cpu_ptr(entry->pool->acomp_ctx);
> +
>  		dlen = PAGE_SIZE;
>  		src = (u8 *)zhdr + sizeof(struct zswap_header);
> -		dst = kmap_atomic(page);
> -		tfm = *get_cpu_ptr(entry->pool->tfm);
> -		ret = crypto_comp_decompress(tfm, src, entry->length,
> -					     dst, &dlen);
> -		put_cpu_ptr(entry->pool->tfm);
> -		kunmap_atomic(dst);
> +		dst = kmap(page);
> +
> +		mutex_lock(acomp_ctx->mutex);
> +		sg_init_one(&input, src, entry->length);
> +		sg_init_one(&output, dst, dlen);
> +		acomp_request_set_params(acomp_ctx->req, &input, &output,
> entry->length, dlen);
> +		ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req),
> &acomp_ctx->wait);
> +		dlen = acomp_ctx->req->dlen;
> +		mutex_unlock(acomp_ctx->mutex);
> +
> +		kunmap(page);
>  		BUG_ON(ret);
>  		BUG_ON(dlen != PAGE_SIZE);
> 
> @@ -1004,7 +1069,8 @@ static int zswap_frontswap_store(unsigned type,
> pgoff_t offset,  {
>  	struct zswap_tree *tree = zswap_trees[type];
>  	struct zswap_entry *entry, *dupentry;
> -	struct crypto_comp *tfm;
> +	struct scatterlist input, output;
> +	struct crypto_acomp_ctx *acomp_ctx;
>  	int ret;
>  	unsigned int hlen, dlen = PAGE_SIZE;
>  	unsigned long handle, value;
> @@ -1074,12 +1140,32 @@ static int zswap_frontswap_store(unsigned type,
> pgoff_t offset,
>  	}
> 
>  	/* compress */
> -	dst = get_cpu_var(zswap_dstmem);
> -	tfm = *get_cpu_ptr(entry->pool->tfm);
> -	src = kmap_atomic(page);
> -	ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
> -	kunmap_atomic(src);
> -	put_cpu_ptr(entry->pool->tfm);
> +	acomp_ctx = this_cpu_ptr(entry->pool->acomp_ctx);
> +
> +	mutex_lock(acomp_ctx->mutex);
> +
> +	src = kmap(page);
> +	dst = acomp_ctx->dstmem;
> +	sg_init_one(&input, src, PAGE_SIZE);
> +	/* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
> +	sg_init_one(&output, dst, PAGE_SIZE * 2);
> +	acomp_request_set_params(acomp_ctx->req, &input, &output,
> PAGE_SIZE, dlen);
> +	/*
> +	 * it maybe looks a little bit silly that we send an asynchronous request,
> +	 * then wait for its completion synchronously. This makes the process
> look
> +	 * synchronous in fact.
> +	 * Theoretically, acomp supports users send multiple acomp requests in
> one
> +	 * acomp instance, then get those requests done simultaneously. but in
> this
> +	 * case, frontswap actually does store and load page by page, there is no
> +	 * existing method to send the second page before the first page is done
> +	 * in one thread doing frontswap.
> +	 * but in different threads running on different cpu, we have different
> +	 * acomp instance, so multiple threads can do (de)compression in
> parallel.
> +	 */
> +	ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req),
> &acomp_ctx->wait);
> +	dlen = acomp_ctx->req->dlen;
> +	kunmap(page);
> +
>  	if (ret) {
>  		ret = -EINVAL;
>  		goto put_dstmem;
> @@ -1103,7 +1189,7 @@ static int zswap_frontswap_store(unsigned type,
> pgoff_t offset,
>  	memcpy(buf, &zhdr, hlen);
>  	memcpy(buf + hlen, dst, dlen);
>  	zpool_unmap_handle(entry->pool->zpool, handle);
> -	put_cpu_var(zswap_dstmem);
> +	mutex_unlock(acomp_ctx->mutex);
> 
>  	/* populate entry */
>  	entry->offset = offset;
> @@ -1131,7 +1217,7 @@ static int zswap_frontswap_store(unsigned type,
> pgoff_t offset,
>  	return 0;
> 
>  put_dstmem:
> -	put_cpu_var(zswap_dstmem);
> +	mutex_unlock(acomp_ctx->mutex);
>  	zswap_pool_put(entry->pool);
>  freepage:
>  	zswap_entry_cache_free(entry);
> @@ -1148,7 +1234,8 @@ static int zswap_frontswap_load(unsigned type,
> pgoff_t offset,  {
>  	struct zswap_tree *tree = zswap_trees[type];
>  	struct zswap_entry *entry;
> -	struct crypto_comp *tfm;
> +	struct scatterlist input, output;
> +	struct crypto_acomp_ctx *acomp_ctx;
>  	u8 *src, *dst;
>  	unsigned int dlen;
>  	int ret;
> @@ -1175,11 +1262,17 @@ static int zswap_frontswap_load(unsigned type,
> pgoff_t offset,
>  	src = zpool_map_handle(entry->pool->zpool, entry->handle,
> ZPOOL_MM_RO);
>  	if (zpool_evictable(entry->pool->zpool))
>  		src += sizeof(struct zswap_header);
> -	dst = kmap_atomic(page);
> -	tfm = *get_cpu_ptr(entry->pool->tfm);
> -	ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
> -	put_cpu_ptr(entry->pool->tfm);
> -	kunmap_atomic(dst);
> +	dst = kmap(page);
> +
> +	acomp_ctx = this_cpu_ptr(entry->pool->acomp_ctx);
> +	mutex_lock(acomp_ctx->mutex);
> +	sg_init_one(&input, src, entry->length);
> +	sg_init_one(&output, dst, dlen);
> +	acomp_request_set_params(acomp_ctx->req, &input, &output,
> entry->length, dlen);
> +	ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req),
> &acomp_ctx->wait);
> +	mutex_unlock(acomp_ctx->mutex);
> +
> +	kunmap(page);
>  	zpool_unmap_handle(entry->pool->zpool, entry->handle);
>  	BUG_ON(ret);
> 
> --
> 2.27.0

Thanks
Barry

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