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Message-ID: <CAKEwX=MCqHwUA5mH4kPdG4O0joqeHvjUhT8rD42avQxJg7hnxA@mail.gmail.com>
Date: Tue, 30 Jan 2024 08:21:31 -0800
From: Nhat Pham <nphamcs@...il.com>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Yosry Ahmed <yosryahmed@...gle.com>,
Chengming Zhou <zhouchengming@...edance.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/20] mm: zswap: break out zwap_compress()
On Mon, Jan 29, 2024 at 5:42 PM Johannes Weiner <hannes@...xchg.org> wrote:
>
> zswap_store() is long and mixes work at the zswap layer with work at
> the backend and compression layer. Move compression & backend work to
> zswap_compress(), mirroring zswap_decompress().
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
> mm/zswap.c | 145 ++++++++++++++++++++++++++++-------------------------
> 1 file changed, 77 insertions(+), 68 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index bdc9f82fe4b9..f9b9494156ba 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1316,6 +1316,79 @@ static int zswap_enabled_param_set(const char *val,
> return ret;
> }
>
> +static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
> +{
> + struct crypto_acomp_ctx *acomp_ctx;
> + struct scatterlist input, output;
> + unsigned int dlen = PAGE_SIZE;
> + unsigned long handle;
> + struct zpool *zpool;
> + char *buf;
> + gfp_t gfp;
> + int ret;
> + u8 *dst;
> +
> + acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> +
> + mutex_lock(&acomp_ctx->mutex);
> +
> + dst = acomp_ctx->buffer;
> + sg_init_table(&input, 1);
> + sg_set_page(&input, &folio->page, PAGE_SIZE, 0);
> +
> + /*
> + * We need PAGE_SIZE * 2 here since there maybe over-compression case,
> + * and hardware-accelerators may won't check the dst buffer size, so
> + * giving the dst buffer with enough length to avoid buffer overflow.
> + */
> + 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, zswap 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 zwap.
> + * 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;
> + if (ret) {
> + zswap_reject_compress_fail++;
> + goto unlock;
> + }
> +
> + zpool = zswap_find_zpool(entry);
> + gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
> + if (zpool_malloc_support_movable(zpool))
> + gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
> + ret = zpool_malloc(zpool, dlen, gfp, &handle);
> + if (ret == -ENOSPC) {
> + zswap_reject_compress_poor++;
> + goto unlock;
> + }
> + if (ret) {
> + zswap_reject_alloc_fail++;
> + goto unlock;
> + }
> +
> + buf = zpool_map_handle(zpool, handle, ZPOOL_MM_WO);
> + memcpy(buf, dst, dlen);
> + zpool_unmap_handle(zpool, handle);
> +
> + entry->handle = handle;
> + entry->length = dlen;
> +
> +unlock:
> + mutex_unlock(&acomp_ctx->mutex);
> + return ret == 0;
> +}
> +
> static void zswap_decompress(struct zswap_entry *entry, struct page *page)
> {
> struct zpool *zpool = zswap_find_zpool(entry);
> @@ -1472,18 +1545,11 @@ bool zswap_store(struct folio *folio)
> struct page *page = &folio->page;
> struct zswap_tree *tree = swap_zswap_tree(swp);
> struct zswap_entry *entry, *dupentry;
> - struct scatterlist input, output;
> - struct crypto_acomp_ctx *acomp_ctx;
> struct obj_cgroup *objcg = NULL;
> struct mem_cgroup *memcg = NULL;
> struct zswap_pool *pool;
> - struct zpool *zpool;
> - unsigned int dlen = PAGE_SIZE;
> - unsigned long handle, value;
> - char *buf;
> - u8 *src, *dst;
> - gfp_t gfp;
> - int ret;
> + unsigned long value;
> + u8 *src;
>
> VM_WARN_ON_ONCE(!folio_test_locked(folio));
> VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
> @@ -1568,65 +1634,10 @@ bool zswap_store(struct folio *folio)
> mem_cgroup_put(memcg);
> }
>
> - /* compress */
> - acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> -
> - mutex_lock(&acomp_ctx->mutex);
> -
> - dst = acomp_ctx->buffer;
> - sg_init_table(&input, 1);
> - sg_set_page(&input, &folio->page, PAGE_SIZE, 0);
> + if (!zswap_compress(folio, entry))
> + goto put_pool;
>
> - /*
> - * We need PAGE_SIZE * 2 here since there maybe over-compression case,
> - * and hardware-accelerators may won't check the dst buffer size, so
> - * giving the dst buffer with enough length to avoid buffer overflow.
> - */
> - 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, zswap 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 zwap.
> - * 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;
> -
> - if (ret) {
> - zswap_reject_compress_fail++;
> - goto put_dstmem;
> - }
> -
> - /* store */
> - zpool = zswap_find_zpool(entry);
> - gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
> - if (zpool_malloc_support_movable(zpool))
> - gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
> - ret = zpool_malloc(zpool, dlen, gfp, &handle);
> - if (ret == -ENOSPC) {
> - zswap_reject_compress_poor++;
> - goto put_dstmem;
> - }
> - if (ret) {
> - zswap_reject_alloc_fail++;
> - goto put_dstmem;
> - }
> - buf = zpool_map_handle(zpool, handle, ZPOOL_MM_WO);
> - memcpy(buf, dst, dlen);
> - zpool_unmap_handle(zpool, handle);
> - mutex_unlock(&acomp_ctx->mutex);
> -
> - /* populate entry */
> entry->swpentry = swp;
> - entry->handle = handle;
> - entry->length = dlen;
>
> insert_entry:
> entry->objcg = objcg;
> @@ -1663,8 +1674,6 @@ bool zswap_store(struct folio *folio)
>
> return true;
>
> -put_dstmem:
> - mutex_unlock(&acomp_ctx->mutex);
> put_pool:
> zswap_pool_put(entry->pool);
> freepage:
> --
> 2.43.0
>
LGTM :)
Reviewed-by: Nhat Pham <nphamcs@...il.com>
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