Re: [Xen-devel] Insane contiguous physical memory requirements in blkbk/blktap

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 5/10/06 17:40, "Stephen C. Tweedie" <sct@xxxxxxxxxx> wrote:

> OK, I was looking at blkback in this case.  Indexing is easy, we already
> have page->index for that purpose, and I don't think there's anything
> else using that for these pages once they are detached from the main VM.
> 
> Is there any reason we're not using memory in the vmalloc area for these
> things?  That memory is *supposed* to be allocated out for virtual use
> on demand.

In most cases we want the 'struct page' as well as the virtual address
space. For example, to stuff into skbuff fragment lists or block-device
scatter-gather lists. Kmalloc() gets us both those things -- it's just the
underlying mapped RAM we don't want. ;-)

 -- Keir



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