Re: [PATCH] add new DMA_ADDR_T_SIZE define

[David S. Miller]

   From: Ion Badulescu <[e-mail]>
   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.