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From: Binoy Jayan <>
To: Ondrej Mosnacek <>
Cc: Herbert Xu <>,,,
	Mike Snitzer <>,
	Milan Broz <>,
	Mikulas Patocka <>,
	Mark Brown <>, Arnd Bergmann <>
Subject: Re: [RFC PATCH 6/6] dm-crypt: Add bulk crypto processing support
Date: Mon, 16 Jan 2017 14:07:37 +0530	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi Ondrej,

On 12 January 2017 at 18:29, Ondrej Mosnacek <> wrote:
> This patch converts dm-crypt to use bulk requests when invoking skcipher
> operations, allowing the crypto drivers to process multiple sectors at once,
> while reducing the overhead caused by the small sector size.
> The new code detects if multiple sectors from a bio are contigously stored
> within a single page (which should almost always be the case), and in such case
> processes all these sectors via a single bulk request.
> Note that the bio can also consist of several (likely consecutive) pages, which
> could be all bundled in a single request. However, since we need to specify an
> upper bound on how many sectors we are going to send at once (and this bound
> may affect the amount of memory allocated per single request), it is best to
> just limit the request bundling to a single page.

The initial goal of our proposal was to process the encryption requests with the
maximum possible block sizes with a hardware which has automated iv generation
capabilities. But when it is done in software, and if the bulk
requests are processed
sequentially, one block at a time, the memory foot print could be
reduced even if
the bulk request exceeds a page. While your patch looks good, there
are couple of
drawbacks one of which is the maximum size of a bulk request is a page. This
could limit the capability of the crypto hardware. If the whole bio is
processed at
once, which is what qualcomm's version of dm-req-crypt does, it achieves an even
better performance.

> Note that if the 'keycount' parameter of the cipher specification is set to a
> value other than 1, dm-crypt still sends only one sector in each request, since
> in such case the neighboring sectors are encrypted with different keys.

This could be avoided if the key management is done at the crypto layer.


  reply	other threads:[~2017-01-16  8:37 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-12 12:59 [RFC PATCH 0/6] Add bulk skcipher requests to crypto API and dm-crypt Ondrej Mosnacek
2017-01-12 12:59 ` [RFC PATCH 1/6] crypto: skcipher - Add bulk request processing API Ondrej Mosnacek
2017-01-12 12:59 ` [RFC PATCH 2/6] crypto: skcipher - Add bulk request support to walk Ondrej Mosnacek
2017-01-12 12:59 ` [RFC PATCH 3/6] crypto: cryptd - Add skcipher bulk request support Ondrej Mosnacek
2017-01-12 12:59 ` [RFC PATCH 4/6] crypto: simd - Add " Ondrej Mosnacek
2017-01-12 12:59 ` [RFC PATCH 5/6] crypto: aesni-intel " Ondrej Mosnacek
2017-01-13  3:19   ` Eric Biggers
2017-01-13 11:27     ` Ondrej Mosnáček
2017-01-12 12:59 ` [RFC PATCH 6/6] dm-crypt: Add bulk crypto processing support Ondrej Mosnacek
2017-01-16  8:37   ` Binoy Jayan [this message]
2017-01-17 11:15     ` Ondrej Mosnáček
2017-01-13 10:41 ` [RFC PATCH 0/6] Add bulk skcipher requests to crypto API and dm-crypt Herbert Xu
2017-01-13 12:01   ` Ondrej Mosnáček
2017-01-13 14:29     ` Herbert Xu
2017-01-17 11:20       ` Ondrej Mosnáček
2017-01-18  4:48         ` Herbert Xu
2017-01-19 14:21           ` Ondrej Mosnáček
2017-01-23 13:04             ` Herbert Xu
2017-01-18 17:09     ` Binoy Jayan

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