Rob van der Heij writes: > Malcolm Beattie wrote: > > > Start with > > # echo 262144 > /proc/sys/net/core/wmem_max > > # echo 262144 > /proc/sys/net/core/rmem_max > > to raise the maximum read/write buffer size internally from 64K to 256K. > > And you did not even ask whether he's running on VM or not. > The virtual machine not being dispatched by CP in time can be a > cause for packet loss and require retransmission, in which case > a large tcp window might even make you go slower. Given enough > competition the same would apply to LPARs with shared CPUs.
Good point. My bad. > I'm not sure where your 256K comes from, but I would be very > reluctant to spread this kind of rules-of-thumb. I did some investigation and test of high performance networking with Gig-Eth (non-390) and raising that limit helped. I also did some tests with 390 networking performance (vctc and iucv under vm) and tweaked some other things. I hadn't thought carefully enough that the rmem_max/wmem_max change wouldn't be a generic speedup. > reluctant to spread this kind of rules-of-thumb. I'm afraid > QDIO performance turns out to be more complicated than this. Yeah, I know... :-) --Malcolm -- Malcolm Beattie <[EMAIL PROTECTED]> Linux Technical Consultant IBM EMEA Enterprise Server Group... ...from home, speaking only for myself
