linux-kernel - Re: [PATCH 02/16] f2fs: add on-disk layout

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Date:	Sat, 13 Oct 2012 20:39:48 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	±èÀç±Ø <jaegeuk.kim@...sung.com>,
	viro@...iv.linux.org.uk, 'Theodore Ts'o' <tytso@....edu>,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	chur.lee@...sung.com, cm224.lee@...sung.com,
	jooyoung.hwang@...sung.com
Subject: Re: [PATCH 02/16] f2fs: add on-disk layout

2012-10-12 (ê¸ˆ), 21:05 +0000, Arnd Bergmann:
> On Friday 05 October 2012 20:56:44 ê¹€ìž¬ê·¹ wrote:
> > +struct f2fs_nat_entry {
> > +       __u8 version;
> > +       __le32 ino;
> > +       __le32 block_addr;
> > +} __packed;
> > +
> > +struct f2fs_nat_block {
> > +       struct f2fs_nat_entry entries[NAT_ENTRY_PER_BLOCK];
> > +} __packed;
> 
> Using "__packed" on structure is rather inefficient on CPU architectures
> that cannot do aligned accesses. I would suggest you remove this
> attribute everywhere you can. The f2fs_nat_entry is particularly
> suboptimal because it is 9 bytes long, and I'm not sure if this
> can be reasonably changed to a multiple of four.
> 
> In all other cases, you should try to lay out the structures
> so that each member is naturally aligned and you don't need any __packed
> attributes, in particular for those that are accessed a lot.
> 

Ok, I'll check all the in-memory data structures.
Thank you for comments.

> 	Arnd
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-- 
Jaegeuk Kim
Samsung

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