On Fri, Jul 15, 2011 at 10:27:17AM +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? Sorry, I'm not sure -- I never tested it to that granularity, and I don't have access to the hardware anymore now. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>