Well I finally was able to schedule a power on reset changing chparm=00
to chparm=C0 on the hipersockets iocp definition. I then added mtu=57344 to
ifcfg-hsi0, did an ifdown and ifup for hsi0. I then changed vse's tcpip
definition to mtu=57344. I conducted another test and the time it took to
perform a back up to a virtual tape almost doubled from when it was set to 8192.
I ran a utility available on vse tcpip called discover and it reported
back that the best MTU that was successful to get to the linux vm is 1501.
Ifconfig and tcpip on vse shows an mtu of 57344 for the hipersockets link.
Any suggestions on what to look at?
Thanks
Zoltan
-----Original Message-----
From: Herczeg, Zoltan
Sent: Monday, February 13, 2012 11:30 AM
To: LINUX-390@VM.MARIST.EDU
Subject: RE: <No subject given>
I am currently running 8192 MTU size and the current CHPARM is 00. We are not
cpu constrained so I will update the iocp and schedule a power on reset and
take it from there.
Thanks for the suggestions!
Zoltan
-----Original Message-----
From: Alan Altmark [mailto:alan_altm...@us.ibm.com]
Sent: Thursday, February 09, 2012 11:32 AM
Subject: <No subject given>
On Thursday, 02/09/2012 at 09:45 EST, "Herczeg, Zoltan"
<zol...@krasdalefoods.com> wrote:
> DEFINE LINK,ID=HIPER-B04,TYPE=OSAX,DEV=B04,DATAPATH=B0F,MTU=8192, -
> PORTNAME=HIPER-B04,FRAGMENT=NO,IPADDR=9.52.1.24
If you want to use MTU of 8192, Make sure the CHPARM for the HiperSocket chpid
is set to 16K since (MTU = MFS-8192). If you want to use jumbo frames, you'll
need CHPARM of 24K. If you want Really Huge Frame, run the CHPARM up to 64K
and use a 56K MTU. Large MTUs are good for batch streaming.
But remember that HiperSockets uses the z CPUs. If you are CPU-bound, adding
HiperSockets will make things worse. In that case, consider using a shared OSA
port with jumbo frames.
Alan Altmark
Senior Managing z/VM and Linux Consultant IBM System Lab Services and Training
ibm.com/systems/services/labservices
office: 607.429.3323
mobile; 607.321.7556
alan_altm...@us.ibm.com
IBM Endicott
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