2009/9/23 Dave Airlie <airl...@linux.ie>
>
> > > From: Dave Airlie <airl...@redhat.com>
> > >
> > > This avoids needing to do a kmalloc > PAGE_SIZE for the main
> > > indirect buffer chunk, it adds an accessor for all reads from
> > > the chunk and caches a single page at a time for subsequent
> > > reads.
> >
> > FWIW, this works on my PowerBook but seems to drop x11perf -aa10text
> > numbers from about 370k/s to about 315k/s.
>
> Yeah I'm unsure how to bring back up the speed, two ideas I have are:
> 1) won't help you but on PCI/PCIE we can use the IB to read from and avoid
> copying the chunk since its all cache coherent
> 2) keep a bitmap of the pages, copy to the kpage and then to IB, then
> the IB copy from user can just copy any pages we don't hit.
>
> But since what we are doing now is inherently broken, getting order 5
> pages once the system is running is not something we'd expect to work. I
> expect this solution is still faster than the vmalloc overhead.
>
> Dave.
>
>
Maybe only forward iteration could perform better for this parsing. My idea
would be rewrite radeon_get_ib_value like this and correct parser
accordingly. Here it could also just plainly copy directly ths skipped pages
to IB quite easily.
static inline u32 radeon_get_ib_next_value(struct radeon_cs_parser *p,
unsigned skip)
{
int i = p->chunk_ib_idx;
skip += 1; /* advance to next element */
if (unlikely(p->pg_offset + skip >= (PAGE_SIZE/4))) {
/* this could be function call to reduce code size because
this
is relative infrequent operation */
unsigned pages_to_skip;
skip -= (PAGE_SIZE/4) - p->pg_offset;
pages_to_skip = skip/(PAGE_SIZE/4);
skip -= pages_to_skip*(PAGE_SIZE/4);
p->pg_offset = 0;
p->pg_idx += pages_to_skip + 1;
if (DRM_COPY_FROM_USER(p->chunks[i].kpage,
p->chunks[i].user_ptr + (p->pg_idx *
PAGE_SIZE),
PAGE_SIZE))
return 0; /* Should we fail whole parsing here? */
}
p->pg_offset += skip;
return p->chunks[i].kpage[p->pg_offset];
}
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