On 08/26/2014 02:01 PM, Gilad Ben Yossef wrote:
Hi Bill and everyone,
As this is my first post (a few patches not withstanding), I'd like to
start by saying thank you for the work you and everyone are putting into
ODP.
Now for the topic at hand - I know I am a bit of a Johnny-come-lately to
this discussion and a new comer to ODP. I apologize therefore if some of
these issues have been discussed in the past.
The design docs specifies that " Applications cannot address the
contents of a buffer or a buffer segment until they explicitly request
addressability via the odp_buffer_addr(), odp_buffer_segment_addr(), or
odp_buffer_offset_addr() calls. … The provision of this explicit step to
make buffers and buffer segments addressable to an application is for
NUMA architecture support since the actual memory area(s) that store
buffers may not be directly addressable to application processing cores
on such architectures".
However, no API is provided to explicitly state that access to the
segment is no longer needed, thus allowing freeing any resources
required by making the segments available.
Consider as an example an implementation where the odp_buffer_addr()
installs a virtual to physical mapping by populating a hardware MMU
register such as a TLB entry. Without an explicit point where the buffer
data is no longer required to be addressable, there is no point for the
implementation to release said entry.
Hi Gilad
IMO explicit API can be avoided. Application owns buffer until it is
pushed to some queue or consumed by implementation via some other API
(odp_pktio_send, etc). After that point application has no access to
the buffer, so any reserved resources can be cleaned up by
implementation.
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