On 09/01/2009 04:35 PM, Ameya Palande wrote:
Current approach has following problems:
0. It is brain-dead.
1. Caller has to perform 4 system calls in order to map and unmap a buffer.
2. Kernel has no idea about the type of buffer (input/output). So depending
on buffer type caller has to explicitly call DSPProcessor_FlushMemory() or
DSPProcessor_InvalidateMemory().
Proposed approach:
Introduce 2 new IOCTLs which combine (reserve, map) and (unmap, unreserve).
Caller should also specify buffer type (input/output) attribute as a
parameter to new mapping IOCTL.
Benefits of new approach:
1. Saves 2 system calls per map and unmap pair.
2. By implementing lazy unreserve we can introduce cache of reserved
mappings, which can skip reserve, unreserve operations.
3. Kernel can take care of flushing/invalidating cache depending on buffer
type, which saves system call overhead and removed explicit cache control
from user space.
These IOCTLs can be added to the current set of API which doesn't break
compatibility with old applications.
Waiting for comments!
Ideas proposed in this document are from:
1. Hiroshi Doyu<hiroshi.doyu@xxxxxxxxx>
2. Felipe Contreras<felipe.contreras@xxxxxxxxx>
Sounds good for an non-expert.
--
Best Regards,
Artem Bityutskiy (Артём Битюцкий)
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