From: o.evistel@xxxxxxx > Sent: 18 July 2022 15:10 > Hi David > > I try to perform a performance test with a configuration consisting of a M3UA-ASP VM (client) served > by 4 M3UA-SGP VMs (servers). > All the VMs are RHEL8.4. > The TCAP traffic is initiated by the ASP (10K DATA-Chunk/sec) and evenly distributed over the 4 SGPs > which reflect the received traffic to the ASP. > Within a random interval (15 min to several hours) the ASP experiences an error when calling > sctp_sendv() with ERRNO="Resource Temporarily Unavailable". That's looks like a non-blocking send hitting the socket write buffer limit. Almost certainly very transient. Possibly cause by dropped packets or the receiving being overloaded. > As I don't know what causes theese errors I am wondering if this is not a performance issue. > > Referring to your performance test: > - Does 40K reflects/sec mean 40K Tx DATA-Chunk/sec and 40K Rx DATA-Chunk/sec ? Yes. It will be a 'double-reflect' test (both ends reflect) with a smallish number of packets in the loop - enough to get maximum throughput without packets being discarded. > - Did you apply specific kernel parameters tuning (rmem, wmem, ...) ? No. > - Can you share the test program you were using ? It won't help you. It uses our proprietary protocol over TCP to pass TCAP messages into a driver (mostly SCCP, ISUP and MTP3) which uses kernel sockets to do the actual send/recv. > > Thank you in advance for your help and support. > > Regards > Omar AIT AMRANE > ======================================================================================== > > > ----- Mail original ----- > De: "David Laight" <David.Laight@xxxxxxxxxx> > À: "o" <o.evistel@xxxxxxx>, "Marcelo Ricardo Leitner" <marcelo.leitner@xxxxxxxxx> > Cc: "linux-sctp" <linux-sctp@xxxxxxxxxxxxxxx> > Envoyé: Samedi 16 Juillet 2022 14:13:31 > Objet: RE: Linux SCTP performance question > > From: o.evistel@xxxxxxx > > Sent: 13 July 2022 13:59 > > > > I am using linux-sctp as transport for SIGTRAN M3UA on RHEL 8.4 and I am > > using sctp_sendmsg() and sctp_recvmsg() to send/receive. > > I would like to know if the use of sctp_sendv() and sctp_recvv() enhances performances ? > > Every copy to/from a user buffer has a small (but measurable) cost. > So anything with an iov[] array is a bit slower than an equivalent > call that only has a single buffer. > This is measurable when comparing sendmsg() and sendto() on (say) > a UDP socket. > OTOH it is all probably noise unless you are trying to send/receive > 'silly numbers' of messages. > > Reducing the number of system calls may help. > But the cost of recvmmsg() checking for a second message is > significantly greater than using epoll(). > So unless you actually expect lots of messages it probably > isn't worth using. > > Assuming you have disabled Nagle, then the biggest performance > gain will be from setting MSG_MORE when you know you have another > message to send. > Without that pretty much every M3UA message ends up in its own > ethernet packet. > > You don't mention why you think you have a performance issue in SCTP. > I think we got 40000 reflects/sec from a tcap application over M3UA > and SCTP last time I measured out stack. > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
