linux-kernel - Re: [PATCH v3] mm/zswap: move to use crypto

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Message-ID: <20200626072027.GA6153@gondor.apana.org.au>
Date:   Fri, 26 Jun 2020 17:20:27 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Barry Song <song.bao.hua@...ilicon.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        "Luis Claudio R . Goncalves" <lgoncalv@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        "David S . Miller" <davem@...emloft.net>,
        Mahipal Challa <mahipalreddy2006@...il.com>,
        Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        Vitaly Wool <vitaly.wool@...sulko.com>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        Colin Ian King <colin.king@...onical.com>
Subject: Re: [PATCH v3] mm/zswap: move to use crypto_acomp API for hardware
 acceleration

On Fri, Jun 26, 2020 at 07:09:03PM +1200, Barry Song wrote:
>
> +	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);
> +	ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
> +	dlen = acomp_ctx->req->dlen;
> +	kunmap(page);

Waiting on an async request like this is just silly.  This defeats
the whole purpose of having a fallback.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt