> -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Olivier MATZ > Sent: Thursday, March 19, 2015 8:41 AM > To: Neil Horman; vadim.suraev at gmail.com > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH v2] rte_mbuf: mbuf bulk alloc/free functions > added + unittest > > Hi Neil, > > On 03/18/2015 09:58 PM, Neil Horman wrote: > >> +/** > >> + * Free a bulk of mbufs into its original mempool. > >> + * This function assumes: > >> + * - refcnt equals 1 > >> + * - mbufs are direct > >> + * - all mbufs must belong to the same mempool > >> + * > >> + * @param mbufs > >> + * Array of pointers to mbuf > >> + * @param count > >> + * Array size > >> + */ > >> +static inline void rte_pktmbuf_bulk_free(struct rte_mbuf **mbufs, > >> + unsigned count) > >> +{ > >> + unsigned idx; > >> + > >> + RTE_MBUF_ASSERT(count > 0); > >> + > >> + for (idx = 0; idx < count; idx++) { > >> + RTE_MBUF_ASSERT(mbufs[idx]->pool == mbufs[0]->pool); > >> + RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 1); > >> + rte_mbuf_refcnt_set(mbufs[idx], 0); > > This is really a misuse of the API. The entire point of reference counting > > is > > to know when an mbuf has no more references and can be freed. By forcing > > all > > the reference counts to zero here, you allow the refcnt infrastructure to be > > circumvented, causing memory leaks. > > > > I think what you need to do here is enhance the underlying pktmbuf interface > > such that an rte_mbuf structure has a destructor method association with it > > which is called when its refcnt reaches zero. That way the > > rte_pktmbuf_bulk_free function can just decrement the refcnt on each > > mbuf_structure, and the pool as a whole can be returned when the destructor > > function discovers that all mbufs in that bulk pool are freed. > > I don't really understand what's the problem here. The API explicitly > describes the conditions for calling this functions: the segments are > directs, they belong to the same mempool, and their refcnt is 1. > > This function could be useful in a driver which knows that the mbuf > it allocated matches this conditions. I think an application that > only uses direct mbufs and one mempool could also use this function.
I also don't see anything wrong with that function. As long, as user makes sure that all mbufs in the bulk satisfy the required conditions it should be ok, I think. Of course, it's usage is limited, but I suppose the author has some scenario in mind, when introduced it. Konstantin > > Regards, > Olivier
