sglist(9)
John Baldwin
jhb at freebsd.org
Wed May 20 14:02:27 UTC 2009
On Tuesday 19 May 2009 4:34:15 pm Julian Elischer wrote:
> John Baldwin wrote:
> > So one of the things I worked on while hacking away at unmapped disk I/O
> > requests was a little API to manage scatter/gather lists of phyiscal
> > addresses. The basic premise is that a sglist describes a logical object
>
> I was JUST looking at this because of some Linux code I was looking
> at, that uses a predefined sg list that I think it is getting from
> Linux. (you may look to se what the Linux sg list code does/has).
I looked at scatterlist yesterday and it appears to be a bit more DMA-centric
whereas sglist is more intended to describe a range of memory pages.
However, the APIs are somewhat similar (sg_chain() is a lot like
sglist_join() for example). They have a header structure and a list of
scatter/gather elemenets which is also very similar. The one thing they do
differently is that whereas sglist(9) always uses a single array of
scatter/gather list elements of variable length, they allocate "blocks" of
scatter/gather list elements and then chain multiple blocks together if
needed.
--
John Baldwin
More information about the freebsd-arch
mailing list