[dpdk-dev] [PATCH 3/5] mempool: remove optimistic IOVA-contiguous allocation

[Olivier Matz]

On Tue, Oct 29, 2019 at 01:25:10PM +0300, Andrew Rybchenko wrote:
> On 10/28/19 5:01 PM, Olivier Matz wrote:
> > The previous commit reduced the amount of required memory when
> > populating the mempool with non iova-contiguous memory.
> > 
> > Since there is no big advantage to have a fully iova-contiguous mempool
> > if it is not explicitly asked, remove this code, it simplifies the
> > populate function.
> > 
> > Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
> 
> One comment below, other than that
> Reviewed-by: Andrew Rybchenko <arybchenko at solarflare.com>
> 
> > ---
> >   lib/librte_mempool/rte_mempool.c | 47 ++++++--------------------------
> >   1 file changed, 8 insertions(+), 39 deletions(-)
> > 
> > diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
> > index 3275e48c9..5e1f202dc 100644
> > --- a/lib/librte_mempool/rte_mempool.c
> > +++ b/lib/librte_mempool/rte_mempool.c
> 
> [snip]
> 
> > @@ -531,36 +521,15 @@ rte_mempool_populate_default(struct rte_mempool *mp)
> >   			goto fail;
> >   		}
> > -		flags = mz_flags;
> > -
> >   		/* if we're trying to reserve contiguous memory, add appropriate
> >   		 * memzone flag.
> >   		 */
> > -		if (try_iova_contig_mempool)
> > -			flags |= RTE_MEMZONE_IOVA_CONTIG;
> > +		if (min_chunk_size == (size_t)mem_size)
> > +			mz_flags |= RTE_MEMZONE_IOVA_CONTIG;
> >   		mz = rte_memzone_reserve_aligned(mz_name, mem_size,
> > -				mp->socket_id, flags, align);
> > -
> > -		/* if we were trying to allocate contiguous memory, failed and
> > -		 * minimum required contiguous chunk fits minimum page, adjust
> > -		 * memzone size to the page size, and try again.
> > -		 */
> > -		if (mz == NULL && try_iova_contig_mempool &&
> > -				min_chunk_size <= pg_sz) {
> > -			try_iova_contig_mempool = false;
> > -			flags &= ~RTE_MEMZONE_IOVA_CONTIG;
> > -
> > -			mem_size = rte_mempool_ops_calc_mem_size(mp, n,
> > -					pg_shift, &min_chunk_size, &align);
> > -			if (mem_size < 0) {
> > -				ret = mem_size;
> > -				goto fail;
> > -			}
> > +				mp->socket_id, mz_flags, align);
> > -			mz = rte_memzone_reserve_aligned(mz_name, mem_size,
> > -				mp->socket_id, flags, align);
> > -		}
> >   		/* don't try reserving with 0 size if we were asked to reserve
> >   		 * IOVA-contiguous memory.
> >   		 */
> 
> [snip]
> 
> > @@ -587,7 +556,7 @@ rte_mempool_populate_default(struct rte_mempool *mp)
> >   		else
> >   			iova = RTE_BAD_IOVA;
> > -		if (try_iova_contig_mempool || pg_sz == 0)
> > +		if (pg_sz == 0)
> 
> I think (mz_flags & RTE_MEMZONE_IOVA_CONTIG) is lost here.

Do you mean we should do instead
	if (pg_sz == 0 || (mz_flags & RTE_MEMZONE_IOVA_CONTIG))
		populate_iova()
	else
		populate_virt()
?

I would say yes, but it should be removed in patch 5/5.
At the end, we don't want objects to be across pages, even
with RTE_MEMZONE_IOVA_CONTIG.

> 
> >   			ret = rte_mempool_populate_iova(mp, mz->addr,
> >   				iova, mz->len,
> >   				rte_mempool_memchunk_mz_free,
>