linux-kernel - Re: [PATCH v2 2/3] mm/zswap: remove the memcpy if acomp is not sleepable

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Message-ID: <2e35014d-1df3-4efa-8aec-d305094dcd80@bytedance.com>
Date: Fri, 16 Feb 2024 20:38:04 +0800
From: Chengming Zhou <zhouchengming@...edance.com>
To: Barry Song <21cnbao@...il.com>, akpm@...ux-foundation.org,
 davem@...emloft.net, hannes@...xchg.org, herbert@...dor.apana.org.au,
 linux-crypto@...r.kernel.org, linux-mm@...ck.org, nphamcs@...il.com,
 yosryahmed@...gle.com
Cc: chriscli@...gle.com, chrisl@...nel.org, ddstreet@...e.org,
 linux-kernel@...r.kernel.org, sjenning@...hat.com, vitaly.wool@...sulko.com,
 Barry Song <v-songbaohua@...o.com>
Subject: Re: [PATCH v2 2/3] mm/zswap: remove the memcpy if acomp is not
 sleepable

On 2024/2/16 12:08, Barry Song wrote:
> From: Barry Song <v-songbaohua@...o.com>
> 
> Most compressors are actually CPU-based and won't sleep during
> compression and decompression. We should remove the redundant
> memcpy for them.
> 
> Signed-off-by: Barry Song <v-songbaohua@...o.com>
> Tested-by: Chengming Zhou <zhouchengming@...edance.com>
> Reviewed-by: Nhat Pham <nphamcs@...il.com>

LGTM, thanks!

Reviewed-by: Chengming Zhou <zhouchengming@...edance.com>

> ---
>  mm/zswap.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 350dd2fc8159..6319d2281020 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -168,6 +168,7 @@ struct crypto_acomp_ctx {
>  	struct crypto_wait wait;
>  	u8 *buffer;
>  	struct mutex mutex;
> +	bool is_sleepable;
>  };
>  
>  /*
> @@ -716,6 +717,7 @@ 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_sleepable(acomp);
>  
>  	req = acomp_request_alloc(acomp_ctx->acomp);
>  	if (!req) {
> @@ -1368,7 +1370,7 @@ static void __zswap_load(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);
> @@ -1382,7 +1384,7 @@ static void __zswap_load(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);
>  }
>