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

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2016-10-13 17:05, Olivier MATZ:
> 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.

No answer from Wei Dai.
Please Olivier advise what to do with this patch.
Thanks