[PATCH 3/8] ARM: dma-mapping: use asm-generic/dma-mapping-common.h
Russell King - ARM Linux
linux at arm.linux.org.uk
Fri Jul 15 05:27:17 EDT 2011
On Fri, Jul 15, 2011 at 02:10:21AM +0200, Lennert Buytenhek wrote:
> On Thu, Jul 07, 2011 at 01:38:25PM +0100, Russell King - ARM Linux wrote:
> > > > > > I suppose for the majority of the cases, the overhead of the indirect
> > > > > > function call is near-zero, compared to the overhead of the cache
> > > > > > management operation, so it would only make a difference for coherent
> > > > > > systems without an IOMMU. Do we care about micro-optimizing those?
> > >
> > > FWIW, when I was hacking on ARM access point routing performance some
> > > time ago, turning the L1/L2 cache maintenance operations into inline
> > > functions (inlined into the ethernet driver) gave me a significant and
> > > measurable performance boost.
> > On what architecture? Can you show what you did to gain that?
> Patch is attached below. It's an ugly product-specific hack, not
> suitable for upstreaming in this form, etc etc, but IIRC it gave me
> a ~5% improvement on packet routing.
Do you know how much is contributed from each change - L1, L2, moving
dma_cache_maint() inline, removing the virt_addr_valid() etc?
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