Messages in this thread |  | | Date | Fri, 2 Feb 2001 12:51:35 +0100 | From | Christoph Hellwig <> | Subject | Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait /notify + callback chains |
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On Thu, Feb 01, 2001 at 09:25:08PM +0000, Stephen C. Tweedie wrote: > > No. Just allow passing the multiple of the devices blocksize over > > ll_rw_block. > > That was just one example: you need the sub-ios just as much when > you split up an IO over stripe boundaries in LVM or raid0, for > example.
IIRC that's why you designed (and I thought of independandly) clone-kiobufs.
> Secondly, ll_rw_block needs to die anyway: you can expand > the blocksize up to PAGE_SIZE but not beyond, whereas something like > ll_rw_kiobuf can submit a much larger IO atomically (and we have > devices which don't start to deliver good throughput until you use > IO sizes of 1MB or more).
Completly agreed.
> If I've got a vector (page X, offset 0, length PAGE_SIZE) and I want > to split it in two, I have to make two new vectors (page X, offset 0, > length n) and (page X, offset n, length PAGE_SIZE-n). That implies > copying both vectors. > > If I have a page vector with a single offset/length pair, I can build > a new header with the same vector and modified offset/length to split > the vector in two without copying it.
You just say in the higher-level structure ignore from x to y even if they have an offset in their own vector.
Christoph
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