linux-kernel - Re: [PATCH v4 2/6] mm/zswap: reuse dstmem when decompress

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Message-ID: <ZY1EnEefZsRTGYnP@gondor.apana.org.au>
Date: Thu, 28 Dec 2023 17:49:16 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Barry Song <21cnbao@...il.com>
Cc: Chengming Zhou <zhouchengming@...edance.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Seth Jennings <sjenning@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Vitaly Wool <vitaly.wool@...sulko.com>,
	Nhat Pham <nphamcs@...il.com>, Chris Li <chriscli@...gle.com>,
	Yosry Ahmed <yosryahmed@...gle.com>,
	Dan Streetman <ddstreet@...e.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Chris Li <chrisl@...nel.org>
Subject: Re: [PATCH v4 2/6] mm/zswap: reuse dstmem when decompress

On Thu, Dec 28, 2023 at 09:03:32PM +1300, Barry Song wrote:
>
> for CPU-based alg, we have completed the compr/decompr within
> crypto_acomp_decompress()
> synchronously. they won't return EINPROGRESS, EBUSY.
> 
> The problem is that crypto_acomp won't expose this information to its
> users. if it does,
> we can use this info, we will totally avoid the code of copying
> zsmalloc's data to a tmp
> buffer for the most majority users of zswap.
> 
> But I am not sure if we can find a way to convince Herbert(+To)  :-)

What would you like to expose? The async status of the underlying
algorithm?

We could certainly do that.  But I wonder if it might actually be
better for you to allocate a second sync-only algorithm for such
cases.  I'd like to see some real numbers.

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