On 3 Feb 2010 at 23:52, Jack Z wrote:

> Hi Mike,
> 
> Thank you for being so helpful!
> 
> >
> > What are you working on btw?
> 
> I observed a throughput degradation of open-iscsi over long RTT links.
> I'm trying to understand the nature of this performance degradation
> and possibly come up with some solution.

The obvious two solutions are:

1) sending larger packets (which is unrealistic at some point)

2) sending more unconfirmed packets (which is also unrealistic at some 
point)

3) Moving closer ;-)

Ulrich


> 
> Thanks again,
> Jack
> 
> 
> On Feb 3, 2:36 am, Mike Christie <micha...@cs.wisc.edu> wrote:
> > On 02/02/2010 09:57 PM, Jack Z wrote:
> >
> >
> >
> >
> >
> > > Hi all,
> >
> > > In the source code of ver 2.0.871 there's a struct
> >
> > > struct iscsi_segment {
> > >    unsigned char           *data;
> > >    unsigned int            size;
> > >    unsigned int            copied;
> > >    unsigned int            total_size;
> > >    unsigned int            total_copied;
> >
> > >    ......
> >
> > >    iscsi_segment_done_fn_t *done;
> > > };
> >
> > > My understanding is that "copied" is how many bytes are sent out in
> > > the last round and "total_copied" is an accumulative value of how many
> > > bytes have been sent out. Is that correct?
> >
> > > And what do "size" and "total_size" mean respectively?
> >
> > The segment represents the header or data segment that needs to be sent.
> > That segment has a total_size which is all the bytes that need to be
> > sent/recvd for it to be completely sent. The segment->size is what we
> > are currently trying to send/recv for that segment. So we could have a
> > data segment of 128K (so we want to send/recv 128K bytes), but we end up
> > sending that down a page at a time to the net layer. So
> > segment->totoal_size would be 128K and segment->size would be 4K (page
> > size on x86 would be 4K).
> >
> >
> >
> > > Thank you very much! Any help would be highly appreciated.
> 
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