[dpdk-dev] [EXT] [PATCH 5/5] mempool: prevent objects from being across pages

[Olivier Matz]

On Wed, Oct 30, 2019 at 10:46:31AM +0300, Andrew Rybchenko wrote:
> On 10/29/19 8:25 PM, Vamsi Krishna Attunuru wrote:
> > Hi Olivier,
> > 
> > > -----Original Message-----
> > > From: Olivier Matz <olivier.matz at 6wind.com>
> > > Sent: Monday, October 28, 2019 7:31 PM
> > > To: dev at dpdk.org
> > > Cc: Anatoly Burakov <anatoly.burakov at intel.com>; Andrew Rybchenko
> > > <arybchenko at solarflare.com>; Ferruh Yigit <ferruh.yigit at linux.intel.com>;
> > > Giridharan, Ganesan <ggiridharan at rbbn.com>; Jerin Jacob Kollanukkaran
> > > <jerinj at marvell.com>; Kiran Kumar Kokkilagadda
> > > <kirankumark at marvell.com>; Stephen Hemminger
> > > <sthemmin at microsoft.com>; Thomas Monjalon <thomas at monjalon.net>;
> > > Vamsi Krishna Attunuru <vattunuru at marvell.com>
> > > Subject: [EXT] [PATCH 5/5] mempool: prevent objects from being across
> > > pages
> > > 
> > > External Email
> > > 
> > > ----------------------------------------------------------------------
> > > When populating a mempool, ensure that objects are not located across
> > > several pages, except if user did not request iova contiguous objects.
> > > 
> > > Signed-off-by: Vamsi Krishna Attunuru <vattunuru at marvell.com>
> > > Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
> > > ---
> > >   lib/librte_mempool/rte_mempool.c             | 23 +++++-----------
> > >   lib/librte_mempool/rte_mempool_ops_default.c | 29 ++++++++++++++++++-
> > > -
> > >   2 files changed, 33 insertions(+), 19 deletions(-)
> > > 
> > > diff --git a/lib/librte_mempool/rte_mempool.c
> > > b/lib/librte_mempool/rte_mempool.c
> > > index 7664764e5..b23fd1b06 100644
> > > --- a/lib/librte_mempool/rte_mempool.c
> > > +++ b/lib/librte_mempool/rte_mempool.c
> > > @@ -428,8 +428,6 @@ rte_mempool_get_page_size(struct rte_mempool
> > > *mp, size_t *pg_sz)
> > > 
> > >   	if (!need_iova_contig_obj)
> > >   		*pg_sz = 0;
> > > -	else if (!alloc_in_ext_mem && rte_eal_iova_mode() ==
> > > RTE_IOVA_VA)
> > > -		*pg_sz = 0;
> > >   	else if (rte_eal_has_hugepages() || alloc_in_ext_mem)
> > >   		*pg_sz = get_min_page_size(mp->socket_id);
> > >   	else
> > > @@ -478,17 +476,15 @@ rte_mempool_populate_default(struct
> > > rte_mempool *mp)
> > >   	 * then just set page shift and page size to 0, because the user has
> > >   	 * indicated that there's no need to care about anything.
> > >   	 *
> > > -	 * if we do need contiguous objects, there is also an option to reserve
> > > -	 * the entire mempool memory as one contiguous block of memory,
> > > in
> > > -	 * which case the page shift and alignment wouldn't matter as well.
> > > +	 * if we do need contiguous objects (if a mempool driver has its
> > > +	 * own calc_size() method returning min_chunk_size = mem_size),
> > > +	 * there is also an option to reserve the entire mempool memory
> > > +	 * as one contiguous block of memory.
> > >   	 *
> > >   	 * if we require contiguous objects, but not necessarily the entire
> > > -	 * mempool reserved space to be contiguous, then there are two
> > > options.
> > > -	 *
> > > -	 * if our IO addresses are virtual, not actual physical (IOVA as VA
> > > -	 * case), then no page shift needed - our memory allocation will give
> > > us
> > > -	 * contiguous IO memory as far as the hardware is concerned, so
> > > -	 * act as if we're getting contiguous memory.
> > > +	 * mempool reserved space to be contiguous, pg_sz will be != 0,
> > > +	 * and the default ops->populate() will take care of not placing
> > > +	 * objects across pages.
> > >   	 *
> > >   	 * if our IO addresses are physical, we may get memory from bigger
> > >   	 * pages, or we might get memory from smaller pages, and how
> > > much of it @@ -501,11 +497,6 @@ rte_mempool_populate_default(struct
> > > rte_mempool *mp)
> > >   	 *
> > >   	 * If we fail to get enough contiguous memory, then we'll go and
> > >   	 * reserve space in smaller chunks.
> > > -	 *
> > > -	 * We also have to take into account the fact that memory that we're
> > > -	 * going to allocate from can belong to an externally allocated
> > > memory
> > > -	 * area, in which case the assumption of IOVA as VA mode being
> > > -	 * synonymous with IOVA contiguousness will not hold.
> > >   	 */
> > > 
> > >   	need_iova_contig_obj = !(mp->flags &
> > > MEMPOOL_F_NO_IOVA_CONTIG); diff --git
> > > a/lib/librte_mempool/rte_mempool_ops_default.c
> > > b/lib/librte_mempool/rte_mempool_ops_default.c
> > > index f6aea7662..dd09a0a32 100644
> > > --- a/lib/librte_mempool/rte_mempool_ops_default.c
> > > +++ b/lib/librte_mempool/rte_mempool_ops_default.c
> > > @@ -61,21 +61,44 @@ rte_mempool_op_calc_mem_size_default(const
> > > struct rte_mempool *mp,
> > >   	return mem_size;
> > >   }
> > > 
> > > +/* Returns -1 if object crosses a page boundary, else returns 0 */
> > > +static int check_obj_bounds(char *obj, size_t pg_sz, size_t elt_sz) {
> > > +	if (pg_sz == 0)
> > > +		return 0;
> > > +	if (elt_sz > pg_sz)
> > > +		return 0;
> > > +	if (RTE_PTR_ALIGN(obj, pg_sz) != RTE_PTR_ALIGN(obj + elt_sz - 1,
> > > pg_sz))
> > > +		return -1;
> > > +	return 0;
> > > +}
> > > +
> > >   int
> > >   rte_mempool_op_populate_default(struct rte_mempool *mp, unsigned int
> > > max_objs,
> > >   		void *vaddr, rte_iova_t iova, size_t len,
> > >   		rte_mempool_populate_obj_cb_t *obj_cb, void *obj_cb_arg)
> > > {
> > > -	size_t total_elt_sz;
> > > +	char *va = vaddr;
> > > +	size_t total_elt_sz, pg_sz;
> > >   	size_t off;
> > >   	unsigned int i;
> > >   	void *obj;
> > > 
> > > +	rte_mempool_get_page_size(mp, &pg_sz);
> > > +
> > >   	total_elt_sz = mp->header_size + mp->elt_size + mp->trailer_size;
> > > 
> > > -	for (off = 0, i = 0; off + total_elt_sz <= len && i < max_objs; i++) {
> > > +	for (off = 0, i = 0; i < max_objs; i++) {
> > > +		/* align offset to next page start if required */
> > > +		if (check_obj_bounds(va + off, pg_sz, total_elt_sz) < 0)
> > > +			off += RTE_PTR_ALIGN_CEIL(va + off, pg_sz) - (va +
> > > off);
> > Moving offset to the start of next page and than freeing (vaddr + off + header_size) to pool, this scheme is not aligning with octeontx2 mempool's buf alignment requirement(buffer address needs to be multiple of buffer size).
> 
> It sounds line octeontx2 mempool should have its own populate callback
> which cares about it.
> 

Agree, even the calc_mem_size() should be modified to be rigorous.
Let me draft something in next version, so you can test it.