Re: [00/17] Large Blocksize Support V3

Nick Piggin
2007-04-26T07:48:22Z

Christoph Lameter wrote:
> On Thu, 26 Apr 2007, Nick Piggin wrote:
>
>
>>No I don't want to add another fs layer.
>
>
> Well maybe you could explain what you want. Preferably without redefining
> the established terms?

Support for larger buffers than page cache pages.

>>I still don't think anti fragmentation or defragmentation are a good
>>approach, when you consider the alternatives.
>
>
> I have not heard of any alternatives in this discussion here. Just the old
> line of lets tune the VM here and there and hope it lasts a while longer.

I didn't realise that one was even in the running. How can you "tune" the
VM to handle bigger block sizes?

>>OK, I would like to see them. And also discussions of things like why
>>we shouldn't increase PAGE_SIZE instead.
>
>
> Because 4k is a good page size that is bound to the binary format? Frankly
> there is no point in having my text files in large page sizes. However,
> when I read a dvd then I may want to transfer 64k chunks or when use my
> flash drive I may want to transfer 128k chunks. And yes if a scientific
> application needs to do data dump then it should be able to use very high
> page sizes (megabytes, gigabytes) to be able to continue its work while
> the huge dumps runs at full I/O speed ...

So block size > page cache size... also, you should obviously be using
hardware that is tuned to work well with 4K pages, because surely there
is lots of that around.

--
SUSE Labs, Novell Inc.