linux-kernel - Re: [PATCH 06/13] async_tx: add support for asynchronous GF multiplication

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Message-ID: <49C5699C.8050405@emcraft.com>
Date:	Sun, 22 Mar 2009 01:26:36 +0300
From:	Ilya Yanok <yanok@...raft.com>
To:	Dan Williams <dan.j.williams@...el.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	"linux-raid@...r.kernel.org" <linux-raid@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"neilb@...e.de" <neilb@...e.de>,
	"Sosnowski, Maciej" <maciej.sosnowski@...el.com>,
	Yuri Tikhonov <yur@...raft.com>
Subject: Re: [PATCH 06/13] async_tx: add support for asynchronous GF 	multiplication

Hi Dan,

Dan Williams wrote:
>> Why does it?  I don't see why you'd need to cover the vector-vector case
>> at all, since it doesn't appear anywhere in the algorithms.  Certainly
>> going backwards from a vector-vector set to derive if you can do a
>> scalar-vector multiply when you should have known that in the first
>> place is not really useful.
>>
>>     
>>> Looking closer, the only other caller, async_pq_zero_sum, can be
>>> deleted because it has no users.  So async_pq can become a static
>>> routine in async_r6recov.
>>>
>>>       
>> That's another issue entirely, of course :)
>>
>>     
>
> ...ah, but now I see your point and the root cause of the problem.
> The caller needs to be modified to only require scalar multiplication
> even in this corner case.
>   

Argh... There is no vector-vector multiplication at all! You just need
to swap the 'for' cycles back (as it was in the original patch by me and
Yuri) to get rid of two-dimensional lookup at each step.

Regards, Ilya.

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