lkml.org 
[lkml]   [2006]   [May]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: Extended Volume Manager API
From
Date
On Mon, 01 May 2006 00:26:05 CDT, Circuitsoft Development said:

> Having done my own tests, I've determined that a 5msec timeout to
> determine if a host has crashed would be appropriate. (My test was
> basically looking at ping time over a saturated network - averaged
> about 600 microseconds, topped at 3msec over 10 minutes) I figure that
> 5msec timeout won't add any noticeable lag to the volume manager, as
> most disk seek times are in that range.W

Note that if you're setting 5ms as your timeout for detecting a *crash*,
and your *ping* takes 3ms, that leaves you a whole whopping 2ms. If you
have 1ms scheduler latency at *each* end (remember - you're in userspace
at both ends, right?) you have approximately 0ms left for the remote end to
actually *do* anything, and for the local end to process the reply.

And if the remote end has to issue a syscall during processing the request,
you're basically screwed.

You need to be adding at least 1 zero to that timeout value.
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2006-05-01 09:04    [W:0.071 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site