Rakoczy, Dave wrote: > zLinux assigns the MTU size according to the IQD CHPID definition. > > For sake of discussion lets say I set the CHPID to a Max Frame Size of > 64K, that would give me an MTU size of 56K according to the Doc. > > Where can I control the size of the packets I'll send across the > interface? In the Tape Blocksize / Record length as alluded to in the > Adam's previous note? > > Sorry for all the questions... But I've got to learn this stuff > somewhere. > Hi Dave, others had already, carefully, suggested increasing the Frame-Size/MTU which may buy you some performance depending on the application's TCP/IP usage (streaming/transactional, etc.)
We have seen in testing that the 8KB MTU is optimal for a wide range of application types. But you may want to tune for the absolute most bang-for-the-buck, which usually only works if you dedicate to one application type. Once you get past setting your MTU, you should then consider TCP/IP tuning: On z/OS TCPCONFIG TCPRCVB xxxxxx TCPSENDB xxxxxx On z/Linux in /etc/sysctl.conf: net.ipv4.tcp_rmem = aaaa bbbb cccc net.ipv4.tcp_wmem = aaaa bbbb cccc (set via the sysctl command, read man page) Also in the config files for your interfaces you can increase the number of QDIO buffers. /etc/sysconfig/hardware/hwcfg-qeth-bus-ccw-0.0.xxxx add a line like: QETH_OPTIONS="buffer_count=xxx" The above can be verified using lsqeth. I have not given any exact values because everyones configurations (applications, hardware) will vary, suffice to say that the default values for all of the above are on the low side if you are aiming for higher performance. Also take care because these values will effect *ALL* of your TCP/IP applications not just the new one you are implementing. mark ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
