Re: [00/17] Large Blocksize Support V3

[Nick Piggin]

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.
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