[dpdk-dev] Ring PMD: why are stats counters atomic?
Finally I have some time to have a look to it. On Mon, May 16, 2016 at 3:16 PM, Bruce Richardson wrote: > On Mon, May 16, 2016 at 03:12:10PM +0200, Mauricio V?squez wrote: >> Hello Bruce, >> >> Although having this support does not harm anyone, I am not convinced that >> it is useful, mainly because there exists the single-thread limitation in >> other PMDs. Then, if an application has to use different kind of NICs (i.e, >> different PMDs) it has to implement the locking strategies. On the other >> hand, if an application only uses rte_rings, it could just use the >> rte_ring library. >> >> Thanks, Mauricio V >> > I agree. > If you want, please submit a patch to remove this behaviour and see > if anyone objects to it. If there are no objections, I have no problem > accepting > the patch. > > However, since this is a behaviour change to existing functionality, we may > need to implement function versionning for this for ABI compatibility. Please > take that into account when drafting any patch. > Do you think that versioning is required in this case? If anyone is using a functionality that is not supposed to work in that way, should we care about it? I am not against versioning, I just want to know if it is worthy to do. > Regards, > /Bruce > >> On Tue, May 10, 2016 at 11:36 AM, Bruce Richardson < >> bruce.richardson at intel.com> wrote: >> >> > On Tue, May 10, 2016 at 11:13:08AM +0200, Mauricio V?squez wrote: >> > > Hello, >> > > >> > > Per-queue stats counters are defined as rte_atomic64_t, in the tx/rx >> > > functions, they are atomically increased if the rings have the multiple >> > > consumers/producer flag enabled. >> > > >> > > According to the design principles, the application should not invoke >> > those >> > > functions on the same queue on different cores, then I think that atomic >> > > increasing is not necessary. >> > > >> > > Is there something wrong with my reasoning?, If not, I am willing to >> > send a >> > > patch. >> > > >> > > Thank you very much, >> > > >> > Since the rte_rings, on which the ring pmd is obviously based, have >> > multi-producer >> > and multi-consumer support built-in, I thought it might be useful in the >> > ring >> > PMD itself to allow multiple threads to access the ring queues at the same >> > time, >> > if the underlying rings are marked as MP/MC safe. When doing enqueues and >> > dequeue >> > from the ring, the stats are either incremented atomically, or >> > non-atomically, >> > depending on the underlying queue type. >> > >> > const uint16_t nb_rx = (uint16_t)rte_ring_dequeue_burst(r->rng, >> > ptrs, nb_bufs); >> > if (r->rng->flags & RING_F_SC_DEQ) >> > r->rx_pkts.cnt += nb_rx; >> > else >> > rte_atomic64_add(&(r->rx_pkts), nb_rx); >> > >> > If people don't think this behaviour is worthwhile keeping, I'm ok with >> > removing >> > it, since all other PMDs have the restriction that the queues are >> > single-thread >> > only. >> > >> > Regards, >> > /Bruce >> > Regards, Mauricio V
[dpdk-dev] Ring PMD: why are stats counters atomic?
Hello Bruce, Although having this support does not harm anyone, I am not convinced that it is useful, mainly because there exists the single-thread limitation in other PMDs. Then, if an application has to use different kind of NICs (i.e, different PMDs) it has to implement the locking strategies. On the other hand, if an application only uses rte_rings, it could just use the rte_ring library. Thanks, Mauricio V On Tue, May 10, 2016 at 11:36 AM, Bruce Richardson < bruce.richardson at intel.com> wrote: > On Tue, May 10, 2016 at 11:13:08AM +0200, Mauricio V?squez wrote: > > Hello, > > > > Per-queue stats counters are defined as rte_atomic64_t, in the tx/rx > > functions, they are atomically increased if the rings have the multiple > > consumers/producer flag enabled. > > > > According to the design principles, the application should not invoke > those > > functions on the same queue on different cores, then I think that atomic > > increasing is not necessary. > > > > Is there something wrong with my reasoning?, If not, I am willing to > send a > > patch. > > > > Thank you very much, > > > Since the rte_rings, on which the ring pmd is obviously based, have > multi-producer > and multi-consumer support built-in, I thought it might be useful in the > ring > PMD itself to allow multiple threads to access the ring queues at the same > time, > if the underlying rings are marked as MP/MC safe. When doing enqueues and > dequeue > from the ring, the stats are either incremented atomically, or > non-atomically, > depending on the underlying queue type. > > const uint16_t nb_rx = (uint16_t)rte_ring_dequeue_burst(r->rng, > ptrs, nb_bufs); > if (r->rng->flags & RING_F_SC_DEQ) > r->rx_pkts.cnt += nb_rx; > else > rte_atomic64_add(&(r->rx_pkts), nb_rx); > > If people don't think this behaviour is worthwhile keeping, I'm ok with > removing > it, since all other PMDs have the restriction that the queues are > single-thread > only. > > Regards, > /Bruce >
[dpdk-dev] Ring PMD: why are stats counters atomic?
On Mon, May 16, 2016 at 03:12:10PM +0200, Mauricio V?squez wrote: > Hello Bruce, > > Although having this support does not harm anyone, I am not convinced that > it is useful, mainly because there exists the single-thread limitation in > other PMDs. Then, if an application has to use different kind of NICs (i.e, > different PMDs) it has to implement the locking strategies. On the other > hand, if an application only uses rte_rings, it could just use the > rte_ring library. > > Thanks, Mauricio V > I agree. If you want, please submit a patch to remove this behaviour and see if anyone objects to it. If there are no objections, I have no problem accepting the patch. However, since this is a behaviour change to existing functionality, we may need to implement function versionning for this for ABI compatibility. Please take that into account when drafting any patch. Regards, /Bruce > On Tue, May 10, 2016 at 11:36 AM, Bruce Richardson < > bruce.richardson at intel.com> wrote: > > > On Tue, May 10, 2016 at 11:13:08AM +0200, Mauricio V?squez wrote: > > > Hello, > > > > > > Per-queue stats counters are defined as rte_atomic64_t, in the tx/rx > > > functions, they are atomically increased if the rings have the multiple > > > consumers/producer flag enabled. > > > > > > According to the design principles, the application should not invoke > > those > > > functions on the same queue on different cores, then I think that atomic > > > increasing is not necessary. > > > > > > Is there something wrong with my reasoning?, If not, I am willing to > > send a > > > patch. > > > > > > Thank you very much, > > > > > Since the rte_rings, on which the ring pmd is obviously based, have > > multi-producer > > and multi-consumer support built-in, I thought it might be useful in the > > ring > > PMD itself to allow multiple threads to access the ring queues at the same > > time, > > if the underlying rings are marked as MP/MC safe. When doing enqueues and > > dequeue > > from the ring, the stats are either incremented atomically, or > > non-atomically, > > depending on the underlying queue type. > > > > const uint16_t nb_rx = (uint16_t)rte_ring_dequeue_burst(r->rng, > > ptrs, nb_bufs); > > if (r->rng->flags & RING_F_SC_DEQ) > > r->rx_pkts.cnt += nb_rx; > > else > > rte_atomic64_add(&(r->rx_pkts), nb_rx); > > > > If people don't think this behaviour is worthwhile keeping, I'm ok with > > removing > > it, since all other PMDs have the restriction that the queues are > > single-thread > > only. > > > > Regards, > > /Bruce > >
[dpdk-dev] Ring PMD: why are stats counters atomic?
Hello, Per-queue stats counters are defined as rte_atomic64_t, in the tx/rx functions, they are atomically increased if the rings have the multiple consumers/producer flag enabled. According to the design principles, the application should not invoke those functions on the same queue on different cores, then I think that atomic increasing is not necessary. Is there something wrong with my reasoning?, If not, I am willing to send a patch. Thank you very much, Mauricio V,
[dpdk-dev] Ring PMD: why are stats counters atomic?
On Tue, May 10, 2016 at 11:13:08AM +0200, Mauricio V?squez wrote: > Hello, > > Per-queue stats counters are defined as rte_atomic64_t, in the tx/rx > functions, they are atomically increased if the rings have the multiple > consumers/producer flag enabled. > > According to the design principles, the application should not invoke those > functions on the same queue on different cores, then I think that atomic > increasing is not necessary. > > Is there something wrong with my reasoning?, If not, I am willing to send a > patch. > > Thank you very much, > Since the rte_rings, on which the ring pmd is obviously based, have multi-producer and multi-consumer support built-in, I thought it might be useful in the ring PMD itself to allow multiple threads to access the ring queues at the same time, if the underlying rings are marked as MP/MC safe. When doing enqueues and dequeue from the ring, the stats are either incremented atomically, or non-atomically, depending on the underlying queue type. const uint16_t nb_rx = (uint16_t)rte_ring_dequeue_burst(r->rng, ptrs, nb_bufs); if (r->rng->flags & RING_F_SC_DEQ) r->rx_pkts.cnt += nb_rx; else rte_atomic64_add(&(r->rx_pkts), nb_rx); If people don't think this behaviour is worthwhile keeping, I'm ok with removing it, since all other PMDs have the restriction that the queues are single-thread only. Regards, /Bruce
