On Fri, Jul 29, 2011 at 03:48:45AM -0600, Andreas Dilger wrote:

On 2011-07-28, at 4:07 PM, Joel Becker wrote:

quoted

	We use ethernet crc32 in ocfs2.  btrfs uses crc32c.  Frankly, I
could have used crc32c if I'd really thought about the hardware
acceleration benefits.  I think it's a good idea for ext4.

The problem with crc32[c] is that if you don't have hardware acceleration
it is terribly slow.

	We find ethernet crc32 just fine in ocfs2.  I use the kernel's
implementation, which survives everyone's network traffic, and of course
we added the triggers to jbd2 so we only have to do the calculations on
read and write.

Yes, it makes sense to just put a "fake" dirent at the end of the leaf block,
or similar.  I don't think it is necessary to modify existing directories or
extent blocks to add these structures in, if there is no room, but for new
blocks, or blocks with space it is enough.

	We have tunefs.ocfs2 code to adjust existing directories to add
the trailer.  It's not too bad, really.
 
Joel

-- 

"People with narrow minds usually have broad tongues."

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			jlbec@evilplan.org