RE: [PATCH 1/2] net/mana: use a MR variable on the stack instead of allocating it

[Long Li <longli@microsoft.com>]

> > From: Long Li <longli@microsoft.com>
> >
> > The content of the MR is copied to the cache trees, it's not necessary
> > to allocate a MR to do this. Use a variable on the stack instead.
> >
> > This also fixes the memory leak in the code where a MR is allocated
> > but never freed.
> >
> 
> patch title describes what is done, but not gives information about reasoning and
> impact.
> 
> Is this a performance improvement (if so how much), or is this a fix for the
> memory leak (if so we need fixes tag for backport), or just a refactoring?

It's for fixing memory leak. I'll send v2 for better wording.

> 
> > Signed-off-by: Long Li <longli@microsoft.com>
> > ---
> >  drivers/net/mana/mr.c | 15 +++++++--------
> >  1 file changed, 7 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/net/mana/mr.c b/drivers/net/mana/mr.c index
> > d6a5ad1460..c9d0f7ef5a 100644
> > --- a/drivers/net/mana/mr.c
> > +++ b/drivers/net/mana/mr.c
> > @@ -40,7 +40,7 @@ mana_new_pmd_mr(struct mana_mr_btree *local_tree,
> struct mana_priv *priv,
> >  	struct ibv_mr *ibv_mr;
> >  	struct mana_range ranges[pool->nb_mem_chunks];
> >  	uint32_t i;
> > -	struct mana_mr_cache *mr;
> > +	struct mana_mr_cache mr;
> >  	int ret;
> >
> >  	rte_mempool_mem_iter(pool, mana_mempool_chunk_cb, ranges); @@
> -75,14
> > +75,13 @@ mana_new_pmd_mr(struct mana_mr_btree *local_tree, struct
> mana_priv *priv,
> >  			DP_LOG(DEBUG, "MR lkey %u addr %p len %zu",
> >  			       ibv_mr->lkey, ibv_mr->addr, ibv_mr->length);
> >
> > -			mr = rte_calloc("MANA MR", 1, sizeof(*mr), 0);
> > -			mr->lkey = ibv_mr->lkey;
> > -			mr->addr = (uintptr_t)ibv_mr->addr;
> > -			mr->len = ibv_mr->length;
> > -			mr->verb_obj = ibv_mr;
> > +			mr.lkey = ibv_mr->lkey;
> > +			mr.addr = (uintptr_t)ibv_mr->addr;
> > +			mr.len = ibv_mr->length;
> > +			mr.verb_obj = ibv_mr;
> >
> >  			rte_spinlock_lock(&priv->mr_btree_lock);
> > -			ret = mana_mr_btree_insert(&priv->mr_btree, mr);
> > +			ret = mana_mr_btree_insert(&priv->mr_btree, &mr);
> >  			rte_spinlock_unlock(&priv->mr_btree_lock);
> >  			if (ret) {
> >  				ibv_dereg_mr(ibv_mr);
> > @@ -90,7 +89,7 @@ mana_new_pmd_mr(struct mana_mr_btree *local_tree,
> struct mana_priv *priv,
> >  				return ret;
> >  			}
> >
> > -			ret = mana_mr_btree_insert(local_tree, mr);
> > +			ret = mana_mr_btree_insert(local_tree, &mr);
> >  			if (ret) {
> >  				/* Don't need to clean up MR as it's already
> >  				 * in the global tree