On Thu, 2010-06-17 at 05:54 -0700, Michael Chan wrote: > FUJITA Tomonori wrote: > > > From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> > > Date: Thu, 17 Jun 2010 13:06:15 +0900 > > Subject: [PATCH] bnx2: fix dma_get_ops compilation breakage > > > > This removes dma_get_ops() prefetch optimization in bnx2. > > > > bnx2 uses dma_get_ops() to see if dma_sync_single_for_cpu() is > > noop. bnx2 does prefetch if it's noop. > > > > But dma_get_ops() isn't available on all the architectures (only the > > architectures that uses dma_map_ops struct have it). Using > > dma_get_ops() in drivers leads to compilation breakage on many > > archtectures. > > > > Currently, we don't have a way to see if dma_sync_single_for_cpu() is > > noop. If it can improve the performance notably, we can add the new > > DMA API for it. > > This prefetch improves performance noticeably when the driver is > handling incoming 64-byte packets at a sustained rate. So why not do it unconditionally? The worst that can happen is that you pull in a stale cache line which will get cleaned in the dma_sync, thus slightly degrading performance on incoherent architectures. Alternatively, come up with a dma prefetch infrastructure ... all you're really doing is hinting to the architecture that you'll sync this region next. James -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
