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Date:   Mon, 26 Jun 2023 18:13:44 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Roberto Sassu <roberto.sassu@huaweicloud.com>,
        Eric Biggers <ebiggers@kernel.org>,
        Stefan Berger <stefanb@linux.ibm.com>,
        Mimi Zohar <zohar@linux.ibm.com>, dmitry.kasatkin@gmail.com,
        Jarkko Sakkinen <jarkko@kernel.org>, keyrings@vger.kernel.org,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
Subject: Re: [v2 PATCH 0/5] crypto: Add akcipher interface without SGs
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On Mon, Jun 26, 2023 at 12:03:04PM +0200, Ard Biesheuvel wrote:
>
> In any case, what I would like to see addressed is the horrid scomp to
> acomp layer that ties up megabytes of memory in scratch space, just to
> emulate the acomp interface on top of scomp drivers, while no code
> exists that makes use of the async nature. Do you have an idea on how
> we might address this particular issue?

The whole reason why need to allocate megabytes of memory is because
of the lack of SG lists in the underlying algorithm.  If they
actually used SG lists and allocated pages as they went during
decompression, then we wouldn't need to pre-allocate any memory
at all.

It's not going to be easy of course since we need to convert
every single algorithm.  Perhaps what we could do in the mean
time is to get the scomp implementations do exponential retries
(e.g., start with allocating size * 2, if that fails then double
it, up to whatever we currently pre-allocate).

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