Re: [dpdk-dev] [PATCH] mempool: fix search of maximum contiguous pages

[Olivier MATZ <olivier.matz@6wind.com>]

Hi Wei,

On 10/13/2016 02:31 PM, Ananyev, Konstantin wrote:
>
>>
>>>>> diff --git a/lib/librte_mempool/rte_mempool.c
>>>>> b/lib/librte_mempool/rte_mempool.c
>>>>> index 71017e1..e3e254a 100644
>>>>> --- a/lib/librte_mempool/rte_mempool.c
>>>>> +++ b/lib/librte_mempool/rte_mempool.c
>>>>> @@ -426,9 +426,12 @@ rte_mempool_populate_phys_tab(struct
>>>>> rte_mempool *mp, char *vaddr,
>>>>>
>>>>>   	for (i = 0; i < pg_num && mp->populated_size < mp->size; i += n) {
>>>>>
>>>>> +		phys_addr_t paddr_next;
>>>>> +		paddr_next = paddr[i] + pg_sz;
>>>>> +
>>>>>   		/* populate with the largest group of contiguous pages */
>>>>>   		for (n = 1; (i + n) < pg_num &&
>>>>> -			     paddr[i] + pg_sz == paddr[i+n]; n++)
>>>>> +			     paddr_next == paddr[i+n]; n++, paddr_next += pg_sz)
>>>>>   			;
>>>>
>>>> Good catch.
>>>> Why not just paddr[i + n - 1] != paddr[i + n]?
>>>
>>> Sorry, I meant 'paddr[i + n - 1] + pg_sz == paddr[i+n]' off course.
>>>
>>>> Then you don't need extra variable (paddr_next) here.
>>>> Konstantin
>>
>> Thank you, Konstantin
>> 'paddr[i + n - 1] + pg_sz = paddr[i + n]' also can fix it and have straight meaning.
>> But I assume that my revision with paddr_next += pg_sz may have a bit better performance.
>
> I don't think there would be any real difference, again it is not performance critical code-path.
>
>> By the way, paddr[i] + n * pg_sz = paddr[i + n] can also resolve it.
>
> Yes, that's one seems even better for me - make things more clear.

Thank you for fixing this.

My vote would go for "addr[i + n - 1] + pg_sz == paddr[i + n]"

If you feel "paddr[i] + n * pg_sz = paddr[i + n]" is clearer, I have no 
problem with it either.

Regards,
Olivier