On 29 April 2016 at 18:28, Zoltan Kiss <[email protected]> wrote:
> > > On 28/04/16 18:08, Bala Manoharan wrote: > >> >> On 28 April 2016 at 21:50, Zoltan Kiss <[email protected] >> <mailto:[email protected]>> wrote: >> >> >> >> On 28/04/16 10:29, Bala Manoharan wrote: >> >> >> On 27 April 2016 at 21:43, Zoltan Kiss <[email protected] >> <mailto:[email protected]> >> <mailto:[email protected] <mailto:[email protected]>>> >> wrote: >> >> Move release to _odp_packet_classifier(), because caller >> has no way to >> know if new_pkt were allocated. In that case there would be >> a double >> free >> on pkt, and new_pkt would be leaked. >> >> >> I am little skeptical about this classifier module freeing up >> the packet >> since the error in CoS can only happen during a wrong >> configuration by >> the application >> >> I'm not sure this is wrong config: >> - cos == NULL shouldn't happen, my understanding is that not setting >> a default queue is impossible (although I haven't found it spelled >> out in the header files explicitly), so this is an internal error >> >> >> Whenever application creates a pktio with enable_classifier field set in >> odp_pktio_params_t then it should call the function >> odp_pktio_default_cos_set() to set the default CoS with the pktio. The >> scenario of cos == NULL will only occur if a pktio is created with >> classification enabled and default CoS not set and hence this is a >> configuration error. >> > > So you say in this case these packets should end up on > entry->s.in_queue[index[idx]].queue in pktin_poll()? Why? Or do you have > something else in mind? > I would say it's better if different pktio's handle this the same way. I am saying we should not generalise the handling for all the different pktio, we need to move this handling to the pktio level so that if in future some pktio wants to change the behaviour it will be possible. The configuration error is a serious issue and applications will be interested to raise alarms for this scenario. > > > >> - (cos->s.queue == NULL || cos->s.pool == NULL) means the packet >> should be dropped. Although I don't know how drop_policy should >> affect this, it's not clear from the description of >> odp_cls_cos_create() >> >> - (entry == NULL) is impossible at the moment, but as you said, in >> the future other callers might make this mistake, so better to be >> prepared. >> - odp_packet_copy() fails means we can't put this packet where it >> supposed to arrive, I think it would be very confusing for the >> application to receive it then >> - queue_enq() failure is again a sign of serious issues >> >> >> pool or queue error could also be transient the pool could get empty >> > > This is not an overload issue, as odp_cls_cos_create() says: > > "@note ODP_QUEUE_INVALID and ODP_POOL_INVALID are valid values for queue > and pool associated with a class of service and when any one of these > values are configured as INVALID then the packets assigned to the CoS gets > dropped." > > The packets are dropped only when pool handle is invalid, but in the case of odp_packet_copy() or queue_enq() error the pool or queue is not invalid it is because the pool does not have sufficient buffers. Packet pools are allocated and deallocated during packet handling and if the rate of incoming packets is higher for a small amount of time the packet pool might get empty and odp_packet_copy() API will fail and in this scenario the pktio can decide either to drop the packet or hold the packet and resend it again. This becomes more important now coz we have added the ability to make any interface as loopback and not just interface with name "loop" > after sometime depending upon the load in the network. Imagine a >> scenario where the application sends a decrypted packet into the >> loopback device for classification and would not want the packet to be >> dropped immediately on transient pool exhaustion but would prefer >> delayed sending of the packet. >> > > Or do you mean when odp_packet_copy() fails? (This second part suggest > that) Still, how would that happen? Currently this call graph looks like > this: > > schedule() > pktin_poll() [currently it can place returned packets on > entry->s.in_queue[index[idx]].queue] > odp_pktin_recv() > [pktio's receive function] > [_odp_packet_classifier() or _odp_packet_cls_enq(), depending on your > pktio] > > At which level should we handle this and how? > > (And I think we still should drop the packets in the other error cases > I've mentioned, in an unified way for all pktios) > > >> >> >> and hence it would be better if the error is percolated >> to the application >> >> The error itself is returned through odp_pktin_recv() when you apply >> the next two patch, but as we discussed if classification is enabled >> it shouldn't be called directly. pktin_poll() will notice that >> though, and print a message, but it won't enqueue when queue_enq() >> fails, see the 3rd patch. >> >> so that he can take some intelligent action ( either >> reconfigure classification and send the packet again or free the >> packet ). >> >> >> This function is only used on the receive side, I'm not sure what >> you mean by "send the packet again". >> >> >> The application might want some specific packets not be dropped under >> any scenario even when there is a rate limiting and in case of loopback >> mode the classifier module is attached directly to the output as if >> there is a physical loopback and hence in that scenario the loopback >> device might want to send the packet again after sometime when the pool >> or queue gets empty rather than dropping it immediately. >> > > So you say the loopback receive function should get back the packets when > odp_packet_copy() fails, and send it again to loopback? > That's a hard question whether its a good idea or not. You can count on > the fact that the packets are never lost there, but you are risking > recovery time during an overload scenario (or maybe even a deadlock, if > nothing else releases buffer from the pool, you'll keep enqueuing the same > packets) This risk of recovery time is dependent on the type of packet and pktio interface and we can not generalise this in classifier. Incase of a control packet or configuration packet the application might not want the packet to be dropped. We can discuss this further in today's ARCH call. Regards, Bala > > > >> >> >> >> >> Regarding the issue of freeing up the packet when a new packet is >> created by the classification module, we can better change the >> signature >> of _odp_packet_classifier() API to receive odp_packet_t as a >> pointer and >> update the pointer with new packet. >> >> The main reason I am against freeing up the packet inside >> classification >> module is that this function is currently called only by >> loopback device >> but in future development it could be called from other sources >> also and >> hence it is better if freeing of the packet during error is done >> by the >> caller rather than classification module. >> >> >> I think we should implement this when we get there, and see it fit >> better. Currently it's broken anyway. >> Plus, why would it be better to release by the caller, rather than >> on the spot? As I explained above, these error cases seems to be >> major internal issues, none of them seem like the caller can do >> anything. >> >> >> Why don't we implement it now rather than change it in the future? >> The caller in this case is also internal functions (eg socket, loopback) >> as _odp_packet_classifier() is an internal function and cannot be >> directly called by the application, so the idea here is whether the >> packets are freed up by _odp_packet_classifier() internal function or >> its caller the socket function both of which are internal functions in >> the linux-generic. I prefer the latter so that any future devices could >> be handled gracefully. >> > > I think it's better if all pktio's handle these errors in the same way, > and by default it is by dropping packets. It's easier to enforce if we > handle that in _odp_packet_classifier() and _odp_packet_cls_enq(). > The only scenario when I can imagine to pass back the packet is when > odp_packet_copy() fails, but even then re-sending might not be a good idea, > as I explained above. > > >> Most importantly the point we both are discussing is very narrow and >> code changes are minimal, If you feel strongly then you can go ahead and >> implement your way now and we can make any change in the future. I don't >> want to drag this discussion and delay this patch any longer. >> >> Regards, >> Bala >> >> >> >> Regards, >> Bala >> >> >> Signed-off-by: Zoltan Kiss <[email protected] >> <mailto:[email protected]> >> <mailto:[email protected] >> >> <mailto:[email protected]>>> >> >> --- >> platform/linux-generic/odp_classification.c | 21 >> ++++++++++++--------- >> platform/linux-generic/pktio/loop.c | 1 - >> 2 files changed, 12 insertions(+), 10 deletions(-) >> >> diff --git a/platform/linux-generic/odp_classification.c >> b/platform/linux-generic/odp_classification.c >> index 3a18a78..a1466fd 100644 >> --- a/platform/linux-generic/odp_classification.c >> +++ b/platform/linux-generic/odp_classification.c >> @@ -734,22 +734,20 @@ int >> _odp_packet_classifier(pktio_entry_t >> *entry, odp_packet_t pkt) >> odp_packet_t new_pkt; >> uint8_t *pkt_addr; >> >> - if (entry == NULL) >> + if (entry == NULL) { >> + odp_packet_free(pkt); >> return -1; >> + } >> >> pkt_hdr = odp_packet_hdr(pkt); >> pkt_addr = odp_packet_data(pkt); >> >> /* Matching PMR and selecting the CoS for the >> packet*/ >> cos = pktio_select_cos(entry, pkt_addr, pkt_hdr); >> - if (cos == NULL) >> - return -1; >> - >> - if (cos->s.pool == NULL) >> - return -1; >> - >> - if (cos->s.queue == NULL) >> + if (cos == NULL || cos->s.queue == NULL || >> cos->s.pool == >> NULL) { >> + odp_packet_free(pkt); >> return -1; >> + } >> >> if (odp_packet_pool(pkt) != >> cos->s.pool->s.pool_hdl) { >> new_pkt = odp_packet_copy(pkt, >> cos->s.pool->s.pool_hdl); >> @@ -762,7 +760,12 @@ int _odp_packet_classifier(pktio_entry_t >> *entry, odp_packet_t pkt) >> >> /* Enqueuing the Packet based on the CoS */ >> queue = cos->s.queue; >> - return queue_enq(queue, >> odp_buf_to_hdr((odp_buffer_t)new_pkt), 0); >> + if (queue_enq(queue, >> odp_buf_to_hdr((odp_buffer_t)new_pkt), >> 0)) { >> + odp_packet_free(new_pkt); >> + return -1; >> + } else { >> + return 0; >> + } >> } >> >> cos_t *pktio_select_cos(pktio_entry_t *entry, const >> uint8_t *pkt_addr, >> diff --git a/platform/linux-generic/pktio/loop.c >> b/platform/linux-generic/pktio/loop.c >> index f6a8c1d..676e98b 100644 >> --- a/platform/linux-generic/pktio/loop.c >> +++ b/platform/linux-generic/pktio/loop.c >> @@ -76,7 +76,6 @@ static int loopback_recv(pktio_entry_t >> *pktio_entry, odp_packet_t pkts[], >> } else { >> >> pktio_entry->s.stats.in_errors += >> odp_packet_len(pkt); >> - odp_packet_free(pkt); >> } >> } >> nbr = j; >> -- >> 1.9.1 >> >> >> >>
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