Re: [PATCH 0/2] Introduce the request handling for dm-crypt

From: Jens Axboe
Date: Thu Nov 12 2015 - 10:26:35 EST

On 11/12/2015 03:04 AM, Mark Brown wrote:
On Thu, Nov 12, 2015 at 04:20:41PM +0800, Baolin Wang wrote:

3. perforamence data
It is just a simple dd test result, and will provide the formal report
in future. But from the simple test, we can see the improvement.

It's probably also worth pointing out that Qualcomm have been shipping
an out of tree implementation of this as a separate module in their BSP
(originally written by Danesh Garg who's on this thread):

Android now wants to encrypt phones and tablets by default and have been
seeing substantial performance hits as a result, we can try to get
people to share performance data from productionish systems but it might
be difficult.

Well, shame on them for developing out-of-tree, looks like they are reaping all the benefits of that.

Guys, we need some numbers, enough with the hand waving. There's no point discussing this further until we know how much of a difference it makes to handle X MB chunks instead of Y MB chunks. As was previously stated, unless there's a _substantial_ performance benefit, this patchset isn't going anywhere.

If there is a huge benefit, we can look into ways of making it actually work. That may not even be a request interface, it could just be proper utilization of plugging for in-dm bio merging.

Jens Axboe

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