Re: [ANNOUNCE 0/6] Open-iSCSI High-Performance Initiator for Linux

[Alex Aizman]

Matt Mackall wrote:

> On Tue, Mar 08, 2005 at 09:51:39PM -0800, Alex Aizman wrote:
>  
>
> > Matt Mackall wrote:
> >
> >    
> >
> > > How big is the userspace client?
> > >
> > >      
> > Hmm.. x86 executable? source?
> >
> > Anyway, there's about 12,000 lines of user space code, and growing. In 
> > the kernel we have approx. 3,300 lines.
> >
> >    
> >
> > > > - 450MB/sec Read on a single connection (2-way 2.4Ghz Opteron, 64KB block 
> > > > size);
> > > >        
> > > With what network hardware and drives, please?
> > >
> > >      
> > Neterion's 10GbE adapters. RAM disk on the target side.
> >    
>
> Ahh.
>
> Snipped my question about userspace deadlocks - that was the important
> one. It is in fact why the sfnet one is written as it is - it
> originally had a userspace component and turned out to be easy to
> deadlock under load because of it.
>
>  
There's (or at least was up until today) an ongoing discussion on our 
mailing list at http://groups-beta.google.com/group/open-iscsi. The 
short and long of it: the problem can be solved, and it will. Couple 
simple things we already do: mlockall() to keep the daemon un-swapped, 
and also looking into potential dependency created by syslog (there's 
one for 2.4 kernel, not sure if this is an issue for 2.6).

The sfnet is a learning experience; it is by no means a proof that it 
cannot be done.

Alex
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