And after doing this, do I still need to specify -tcp-bs in the
globus-url-copy command line? If so, I don`t know how to do this for
lcg-cp.
Cheers,
Rod.
On Thu, 13 Oct 2005, Åke Sandgren wrote:
> On Wed, 2005-10-12 at 21:40 -0700, Rod Walker wrote:
> > Hi,
> > Acting on a tip-off I measured the transfer rate from one of the Canadaian
> > clusters to cern. I discovered that
> > globus-url-copy -tcp-bs 16777216 ....
> > is about 25 times faster than with the default buffer size, 2.5MB/s
> > comapared to 100kB/s.
> >
> > Is this indicative of some bad network setting, routing, ..., or is this
> > to be expected for transatlantic transfers - I mean the size of the
> > improvement.
> >
> > How do I make the LCG utils (lcg-cp) use a larger buffer size?
> > I found some optimizations from SC2/3
> >
> > net.ipv4.tcp_rmem = 1048576 16777216 33554432
> > net.ipv4.tcp_wmem = 1048576 16777216 33554432
> > net.ipv4.tcp_mem = 1048576 16777216 33554432
> > net.core.rmem_max = 16777215
> > net.core.wmem_max = 16777215
> > net.core.rmem_default = 4194303
> > net.core.wmem_default = 4194303
> >
> > Will these mean that globus-url-copy will no longer need the tcp-bs
> > argument?
>
>
> This is quite normal for a non-tuned system.
> For more info read http://www.psc.edu/networking/projects/tcptune/
>
> Setting good [rw]mem values will give you godd long-haul performance
> without consuming too much memory.
> You should NOT touch ipv4.tcp_mem!!! EVER!! (unless of course you are a
> kernel hacker and REALLY know what you are doing)
> You should also not touch the first value of ipv4.tcp_[rw]mem there is
> absolutely no need to do that.
>
> And there is usually no need to touch core.[rw]mem_default since tcp
> doesn't care about that one (only udp and other protocols)
>
> We use
> net/core/rmem_max = 83333333
> net/core/wmem_max = 83333333
>
> net/ipv4/tcp_rmem = 4096 833333 83333333
> net/ipv4/tcp_wmem = 4096 833333 83333333
>
> Also read Documentation/networking/ip-sysctl.txt in the kernel-source to
> understand exactly what the parameters do.
>
--
Rod Walker +1 6042913051
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