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soc:2008:stefanha:journal:week11 [2008/08/08 05:24]
stefanha
soc:2008:stefanha:journal:week11 [2008/08/10 08:31] (current)
stefanha
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 After chatting with Marty today I am focusing again. ​ Discussing Etherboot inspires me to get back to coding! After chatting with Marty today I am focusing again. ​ Discussing Etherboot inspires me to get back to coding!
 +
 +==== Sun 10 Aug ====
 +DMA mapping currently provides a mechanism to "​sync"​ dynamically allocated memory with DMA-capable memory. ​ This allows drivers to update their snapshot of memory shared with the device, or for the driver to change memory seen by the device.
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 +The sync works by copying memory from the source region to the destination region. ​ Drivers that use DMA mapping therefore pay a memory copy performance penalty.
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 +There is a way to avoid syncing which I would like to explore. ​ It also plays well with the concept of DMA pools (memory regions set aside as DMA memory). ​ DMA pools mean that drivers must declare their intention to use DMA memory and reserve an amount of memory. ​ We need to do this because gPXE should not change the memory map once it has been started.
  
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