On Wed, 18 Feb 2009 21:03:59 +0100, Ivan Warren <[email protected]> wrote:
> - IPL time ensuing from having many thousand devices (Lordy.. Issuing > Sense-ID, RDC and read of cyl 0 track 1 - on 10000 devices shouldn't > take but a couple seconds anyway.. What's wrong here.. all modern OSes > do this in a routine manner.. why wouldn't Linux be any different ? > (ok.. maybe I should check with the folks in Böblingen) - is taking an > inordinate amount of time. Modern 2.6 kernels are not doing basic SenseID discovery sequentially anymore, but in parallel. Misbehaved devices get a timeout of 30s (which is really worst case). Typically, only a subset of those discovered devices is set online (where rdc and friends come into play). Userspace is another factor here - I know at least one tool which slows down to a crawl when confronted with more than say 30 devices... But best practices still remain valid, as spelled out in the 'Common Pitfalls' section in the device driver manual :) Namely: Make only those devices visible to your Linux that you really need, and use cio_ignore. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
