Re: [00/17] Large Blocksize Support V3

From: Nick Piggin
Date: Fri Apr 27 2007 - 06:16:27 EST


Christoph Lameter wrote:
On Thu, 26 Apr 2007, Nick Piggin wrote:


But what do you mean with it? A block is no longer a contiguous section of
memory. So you have redefined the term.

I don't understand what you mean at all. A block has always been a
contiguous area of disk.


You want to change the block layer to support larger blocksize than PAGE_SIZE right? So you need to segment that larger block into pieces.

The block is the disk block, which does not get segmented.

What you have is a small layer that tells you which block a pagecache
page points to, and which pagecache page refers to a given block. Just
like we have now only slightly extended.


And you dont care about Mel's work on that level?

I actually don't like it too much because it can't provide a robust
solution. What do you do on systems with small memories, or those that
eventually do get fragmented?


You could f.e. switch off defragmentation and the large block support?

Ahh, then you reboot your machine to access your other filesystems?


Actually, I don't know why people are so excited about being able to
use higher order allocations (I would rather be more excited about
never having to use them). But for those few places that really need
it, I'd rather see them use a virtually mapped kernel with proper
defragmentation rather than putting hacks all through the core code.


Ahh. I knew we were going this way.... Now we have virtual contiguous vs. physical discontiguous.... Yuck hackidihack.

That gives you have the proper infrastructure that is needed to actually
support higher order _physical_ allocations _properly_.

--
SUSE Labs, Novell Inc.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/