Bill Fischofer(Bill-Fischofer-Linaro) replied on github web page:
platform/linux-generic/odp_pool.c
line 80
@@ -403,6 +430,12 @@ static odp_pool_t pool_create(const char *name,
odp_pool_param_t *params,
block_size = ROUNDUP_CACHE_LINE(hdr_size + align + headroom +
data_size + tailroom);
+ /* Allocate extra memory for skipping packet buffers which cross page
+ * boundaries. */
+ if (params->type == ODP_POOL_PACKET)
+ num_extra = 2 * (((uint64_t)(num * block_size) +
+ CONT_PAGE_SIZE - 1) / CONT_PAGE_SIZE);
Comment:
The blocks are contiguous so you're computing how many of them can fit in a 2M
huge page. Since blocks aren't themselves larger than a huge page I don't see
what's wrong with my analysis.
> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
> Fair enough. I agree these sort of considerations should be transparent to
> the application. This will complicate the sort of index-juggling that VPP
> does (see PR #200). We'll have to consider this in the discussions planned
> for Monday's ARCH call.
>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>> I'd call it huge pages if that's the problem you're trying to address. Any
>> jumbo packet is going to cross a 4K boundary if it isn't segmented. I assume
>> that isn't a problem?
>>> Matias Elo(matiaselo) wrote:
>>> Yes, I'm referring to all page sizes >= 2MB, so the same operation is also
>>> done with 1GB pages. I was struggling to figure out a good name for this
>>> define, so all ideas are welcome.
>>>> Matias Elo(matiaselo) wrote:
>>>> Currently this is required for the dpdk pmd drivers only, but if/when we
>>>> are adding support for more drivers this issue is likely to re-emerge.
>>>> IMHO the applications shouldn't have to know about this, so I wouldn't add
>>>> a new parameter.
>>>>> Matias Elo(matiaselo) wrote:
>>>>> Also the extra buffers can cross page boundaries.
>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>> Why the `2 *` factor here? The number of block size "page" crossings is
>>>>>> going to be limited to the rounded up number of pages:
>>>>>>
>>>>>> ```
>>>>>> <--------------------------> "n" pages in size
>>>>>> ---+--------+--- ... ---+---- There can be at most n crossings,
>>>>>> (n - 1) if block happily starts on a page
>>>>>> boundary.
>>>>>>
>>>>>> ```
>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>> Shouldn't this processing be an `odp_pool_param_t` option? Doing this
>>>>>>> unconditionally because "some NICs" may have problems seems unnecessary.
>>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>>> This is somewhat confusing terminology. Pages are typically 4K in
>>>>>>>> size. It seems you're referring to huge pages here. How about systems
>>>>>>>> that configured 1GB huge pages?
https://github.com/Linaro/odp/pull/223#discussion_r143274648
updated_at 2017-10-06 19:17:38
