linux-kernel - Re: [PATCH v2] fix sign extension with 1.5TB usb-storage LBD=y

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Date:	Wed, 22 Apr 2009 14:27:12 +0300
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	Matthew Wilcox <matthew@....cx>
CC:	Dave Hansen <dave@...ux.vnet.ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	mdharm-usb@...-eyed-alien.net,
	linux-usb <linux-usb@...r.kernel.org>,
	usb-storage@...ts.one-eyed-alien.net,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2] fix sign extension with 1.5TB usb-storage LBD=y

On 04/22/2009 02:09 PM, Matthew Wilcox wrote:
> On Wed, Apr 22, 2009 at 10:32:59AM +0300, Boaz Harrosh wrote:
>> These are actually aligned access it might be worth sacrificing a cast
>> to be32/64 for sake of speed.
> 
> "for sake of speed"?  How often do you think we ask a device how large
> it is?  

OK, that was the wrong choice of words, on my part. I meant for sake of
"nobleness". I calculated as a programmer that these are aligned do I make
the extra effort of stating that in code, or I get lazy because it does
not matter?

> How much overhead do you think is incurred by the unaligned code
> if the data happens to be aligned?
> 

Well for BE systems we are already order of magnitude faster by just
using the accessors, so I guess we are already well in the "plus" ;)

This is such a small matter, sorry to bother you about it.
Just that it's a programming style I'm constantly debating with myself,
feel free to ignore it.

The patch looks very good to me as it is.

Thanks
Boaz
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