Messages in this thread | | | Date | Wed, 19 Feb 2003 14:29:52 -0800 (PST) | Subject | Re: [PATCH] add new DMA_ADDR_T_SIZE define | From | "David S. Miller" <> |
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From: Ion Badulescu <ionut@badula.org> Date: Wed, 19 Feb 2003 17:41:39 -0500 (EST)
> Nearly all cards today are 64-bit DMA address descriptors only. > So if anything, this new ifdef will get less and less used over > time. Not true. Even if the only descriptors available are 64-bit, there is no reason why I should have to care about the upper 32 bits when I know that my dma_addr_t will always be 32-bit, at compile time. I can simply memset(0) the entire descriptor and initialize only the bottom 32 bits.
Yes true, storing the two consequetive 32-bit values is better for store buffer compression of the cpu. Using memset is much more inefficient because you push the full set of data once then you push non-compressible stores to the same data through the cpu.
I'm not talking out of my ass, I've measured this. - 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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