Heavy I/O blocks FreeBSD box for several seconds

Hartmann, O. ohartman at zedat.fu-berlin.de
Thu Jul 7 22:51:04 UTC 2011

On 07/07/11 09:04, Andriy Gapon wrote:
> on 07/07/2011 06:11 Steve Kargl said the following:
>> Unfortunately, I have neither the brain capacity and time nor
>> the money to fix the issue.  To solve OP's problem in the
>> short, the simplest solution may be to switch to 4BSD.  Let's
>> face, ULE is not a silver bullet.
> I think that piling up different problems into a single discussion, even if they
> involve a common component (to a certain degree), is not going to help anybody.
> If I have read this thread correctly (and taking the subject line as a witness)
> the OP had a problem with heavy I/O activity screwing up interactivity.  I think
> that it's not the same problem as sub-optimal performance of heavy CPU-bound
> load, which is what you reported if I am not mistaken.

This is quibbling. On heavy loads on networ, disk et cetera, isn't there 
always and also
a CPU bound load?
Whenever this problem came up, it was brought down by force.

Yes, I reported due to the obvious fact that this essential problem 
involves usability of several workstations.
It get more obvious when FreeBSD is used with a GUI. But I also 
realized, as I reported(!), problems on a headless
server, even with several tunings, performed slowly and with increasing 
numbers over time as recommended here
(for instance, kern.sched.preempt_thresh=224 or up to 
kern.sched.preempt_thresh=512, with little effect).

Where, if not here, should such problems be discussed? If we open for 
each dedicated micro-problem a separate thread,
we would never gather that many problems which seem to be related to one 
single well known 'sweet spot'.

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