sachin-saxena replied on github web page:
include/odp/api/spec/pool.h
line 13
@@ -290,10 +290,16 @@ odp_pool_t odp_pool_lookup(const char *name);
/**
* Pool information struct
* Used to get information about a pool.
+ * @note The difference between end_addr & start_addr
+ * will result in buffers address range belong to this pool.
*/
typedef struct odp_pool_info_t {
const char *name; /**< pool name */
odp_pool_param_t params; /**< pool parameters */
+ /** Minimum address of any packet contained in this pool */
+ uintptr_t start_addr;
+ /** Maximum address of any packet contained in this pool */
+ uintptr_t end_addr;
Comment:
I will wait for other's comments, if any, before sending V3 patchset
> sachin-saxena wrote
> 1. Agreed for first suggestion.
> 2. For Second, As per my understanding, the VPP only needs to know the range
> of addresses in order to calculate OFFSET within. VPP doesn't assume/store
> packet address beyond its lifetime (Rx to Tx)
>> sachin-saxena wrote
>> OK. agreed
>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>> The only other ambiguity is whether the address that applications see for a
>>> packet is constant. VPP clearly assumes this but this is not implied by the
>>> ODP spec. The "lifetime" of packet visibility is from the time a call like
>>> `odp_packet_data()` is made until the thread releases the `odp_packet_t`
>>> that was used to obtain this address. If some other thread receives that
>>> handle and calls `odp_packet_data()` there's no requirement or guarantee
>>> that it will get the same address as the previous owner.
>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>> I'd change these to "visible address" rather than "address". The point is
>>>> that the spec says nothing about how packets are represented within an
>>>> implementation. It only states what applications may see by using other
>>>> ODP APIs that manipulate odp_packet_t object.
>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>> I'd delete this note as it's not necessary and not complete for the ODP
>>>>> API spec.
>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>> As we discussed earlier today. We should only need an extension to
>>>>>> `odp_pool_info()` to return the `min_addr` and `max_addr` of any packet
>>>>>> contained in the pool. This can simply be added to the end of the
>>>>>> `odp_pool_info_t` struct. The application (in this case VPP) can then
>>>>>> verify that the range is usable by it (_i.e.,_ is containable in 32
>>>>>> bits) and can store the info it needs to do its indexing from this info.
>>>>>>> Petri Savolainen(psavol) wrote:
>>>>>>> How sparse a "linear pool" may be? All implementations can claim linear
>>>>>>> pool support by returning info.first_addr = 0, info.last_addr =
>>>>>>> (uintptr_t) -1, where address size may be 64bits.
>>>>>>>
>>>>>>> Addresses could be used for debugging, but not much more than that.
>>>>>>> What VPP is going to do with this information ?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>>> @muvarov To your points:
>>>>>>>>
>>>>>>>> 1. No, VPP only deals with packets so there's no need to generalize
>>>>>>>> this since it is an accommodation for VPP, not something we want to
>>>>>>>> encourage other applications to use.
>>>>>>>>
>>>>>>>> 2. We abandoned that approach because it required the application to
>>>>>>>> know how much memory the ODP implementation needed for its internal
>>>>>>>> use, which is not something it can reasonably know. So
>>>>>>>> `odp_pool_create()` is responsible for allocating any shm used by the
>>>>>>>> pool based on input provided by the caller.
>>>>>>>>
>>>>>>>> 3. Agree, the union seems strange here. Since having an output
>>>>>>>> parameter in the `odp_pool_param_t` is not something we want this will
>>>>>>>> have to be reworked anyway.
>>>>>>>>> muvarov wrote
>>>>>>>>> 1) is it needed for tmo and bufs also? why it's on only inside
>>>>>>>>> packets? 2) How memory for *start_addr is allocated in VPP? In
>>>>>>>>> previous version of odp_pool_create() was odp_shm_t parameter which
>>>>>>>>> said to reuse already created shm. Maybe that needs to be
>>>>>>>>> reconsidered. 3) why union is needed? why it's not with uintptr_t ?
>>>>>>>>>> Dmitry Eremin-Solenikov(lumag) wrote:
>>>>>>>>>> @Bill-Fischofer-Linaro yes, this looks like a good approach.
>>>>>>>>>> @sachin-saxena could you please reimplement your PR following
>>>>>>>>>> @Bill-Fischofer-Linaro 's suggestion?
>>>>>>>>>>> Dmitry Eremin-Solenikov(lumag) wrote:
>>>>>>>>>>> Got confused between single-segment packet and linear space for
>>>>>>>>>>> packets, sorry.
>>>>>>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>>>>>>> Yes the existing `seg_len` parameter is set to the minimum size
>>>>>>>>>>>> segment that the application requires. This can be set to be equal
>>>>>>>>>>>> to `max_len` to require single-segment packets.
>>>>>>>>>>>>
>>>>>>>>>>>> However @sachin-saxena mentioned at SFO17 that VPP can deal with
>>>>>>>>>>>> multi-segment packets, though I'm not sure how that works.
>>>>>>>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>>>>>>>> VPP will not run on such platforms without modification. If the
>>>>>>>>>>>>> goal is to not modify VPP then an `odp_pool_capability()` output
>>>>>>>>>>>>> that says whether pools can present a linear interface. During
>>>>>>>>>>>>> Connect @psavol also mentioned that a separate API to get this
>>>>>>>>>>>>> info would be more appropriate than bending the input to
>>>>>>>>>>>>> `odp_pool_create()` to give output parameters.
>>>>>>>>>>>>>
>>>>>>>>>>>>> My personal preference would be something like:
>>>>>>>>>>>>>
>>>>>>>>>>>>> * `odp_pool_capability()` indicates whether pools can be created
>>>>>>>>>>>>> that provide linear addressing.
>>>>>>>>>>>>>
>>>>>>>>>>>>> * An option on `odp_pool_create()` to request a linear pool.
>>>>>>>>>>>>>
>>>>>>>>>>>>> * A new API (or an extension to the existing `odp_pool_info()`
>>>>>>>>>>>>> API) to get the mapping info that VPP needs.
>>>>>>>>>>>>>
>>>>>>>>>>>>> That would seem to be more consistent with overall ODP structure.
>>>>>>>>>>>>>> Dmitry Eremin-Solenikov(lumag) wrote:
>>>>>>>>>>>>>> What will happen for platforms where `odp_packet_t` is not
>>>>>>>>>>>>>> mapped to the virtual memory?
>>>>>>>>>>>>>>> Dmitry Eremin-Solenikov(lumag) wrote:
>>>>>>>>>>>>>>> Isn't setting `seg_len` enough? Maybe we should provide an
>>>>>>>>>>>>>>> updated definition for `seg_len` (e.g. in case `seg_len >
>>>>>>>>>>>>>>> max_len`, always use single segment).
https://github.com/Linaro/odp/pull/200#discussion_r143959959
updated_at 2017-10-11 09:40:21
