I/O or Threading Suffer

[Robert Watson]

On Tue, 20 Jul 2004, Scott Long wrote:

> If you are dd'ing from /dev/random, then you are depleting the entropy
> pool.  Anything else that tries to get random numbers is going to block
> in strange ways.  Trying just dd'ing from /dev/zero and see if that
> makes a difference. 

With Yarrow, /dev/random should just keep on chugging, so this is unlikely
to be the source.  However, lots of /dev/random I/O may take a while to
yield if it's working hard in kernel, so if that is combined with a
scheduling nit of some sort, we could be looking at a starvation issue.

Do we know if this is on a UP box or SMP box, and if so, whether it's
using HTT?  I could try reproducing it here and see if I see the same
thing.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org      Principal Research Scientist, McAfee Research