* Dave Hansen (dave@xxxxxxxx) wrote:
> On 10/07/2013 01:21 PM, Robert C Jennings wrote:
> > + } else {
> > + if (vma)
> > + zap_page_range(vma,
> > + user_start,
> > + (user_end -
> > + user_start),
> > + NULL);
> > + vma = find_vma_intersection(
> > + current->mm,
> > + useraddr,
> > + (useraddr +
> > + PAGE_SIZE));
> > + if (!IS_ERR_OR_NULL(vma)) {
> > + user_start = useraddr;
> > + user_end = (useraddr +
> > + PAGE_SIZE);
> > + } else
> > + vma = NULL;
> > + }
>
> This is pretty unspeakably hideous. Was there truly no better way to do
> this?
I was hoping to find a better way to coalesce pipe buffers and zap
entire VMAs (and it needs better documentation but your argument is with
structure and I agree). I would love suggestions for improving this but
that is not to say that I've abandoned it; I'm still looking for ways
to make this cleaner.
Doing find_vma() on a single page in the VMA rather than on each and
then zapping once provides a 50% runtime reduction for the writer when
tested with a 256MB vmsplice operation. Based on the result I felt that
coalescing was justfied but the implementation is ugly.
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