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On Wed, 20 Sep 2006, Martin J. Bligh wrote: > Having something that's used in generic code that means random > things on different arches just seems like a recipe for disaster > to me. ZONE_DMA is only used as ZONE_NORMAL if the architecture does not need ZONE_NORMAL because all of memory is reachable via DMA. > OK ... but requesting ZONE_DMA means what? DMAable for which device? > Is it always a floppy disk? on some platforms a PCI card? And how > is the VM meant to know what the device is capable of anyway? I already explained that twice to you. I think we all agree that the situation could be better. > Having an arch-specific definition of the limit is arbitrary and > useless, is it not? The limit is imposed by the device and its > driver, we're not communicating it into any sensible way into the > VM code, AFAICS. Unless we're pretending we never call it from > generic code, which seems woefully unlikely to me. Its bad but its not useless. See how various arches use it. > Are we redefining ZONE_DMA to always be 16MB limit across all > architectures? At least that'd be consistent. That wont work because many architectures use different limits. Maybe you should once in a while have a look at the sources. The patchset leaves the semantics of ZONE_DMA as memory beyond MAX_DMA_ADDRESS as is. Nothing should break. It only allows us to opt out of this scheme if we do not need it. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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