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

From: Alex Aizman
Date: Wed Mar 09 2005 - 01:29:14 EST

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.


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 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.

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