linux-ext4 - Re: [RFC] delayed allocation for ext4

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Date:	Sat, 23 Dec 2006 22:09:57 +0300
From:	Alex Tomas <alex@...sterfs.com>
To:	David Chinner <dgc@....com>
Cc:	Alex Tomas <alex@...sterfs.com>, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] delayed allocation for ext4

Good day,

>>>>> David Chinner (DC) writes:

 DC> So that mean's we'll have 2 separate mechanisms for marking
 DC> pages as delalloc. XFS uses the BH_delay flag to indicate
 DC> that a buffer (block) attached to the page is using delalloc.

well, for blocksize=pagesize we can save 56 bytes on every page.

 DC> FWIW, how does this mechanism deal with block size < page size?
 DC> Don't you have to track delalloc on a block basis rather than
 DC> a page basis?

I'm still thinking how better to deal with that w/o much code duplication.

 DC> Ah, that's why you can get away with a page flag - you've ignored
 DC> the partial page delay state problem. Any plans to use the
 DC> existing method in the future so we will be able to use ext4 delalloc
 DC> on machines with a page size larger than 4k?

what do you mean by "exsiting"? BH_delay?

thanks, Alex
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