Hello,
On Samstag, 11. September 2004, Greg Kochanski wrote:
> Andreas Metzler wrote:
> >This is <http://bugs.debian.org/270735>. - I'll first quote the
> >One of the obvious points is "reasonable value like 1.5 or 2". A
> >machine with load 2 (e.g. building two software packages) still can
> >receive and deliver mail without breaking into sweat, especially in
> >the scenario the submitter was targeting, e-mail just being one of
> >many services, i.e. rather light traffic.
>
> If the machine is serving nothing but e-mail,
> then there is no point in allowing the load to exceed about 2.
> At that point, the processor and/or disk will be fully occupied,
> and further increases in load will not result in any large
> increase in throughput. For large values of load (e.g. 10),
> you'll start to lose efficiency as the machine is doing
> more context switches.
This is not true for all systems. As far as I know, and I can
stress this point from experience, there are vast differences
in the algorithms used to determine the load value in different
architectures/operating systems. Additionally, there is always
performance, load and throuput to be put together in order to
receive a real picture. I have seen a hp rx2600 (dual itanium)
with load around 10 firing out dramatically more mails than a
PC with a load <1 could ever dream of.
> I'm not 100% satisfied with my suggested solution,
> but the problem of a hard limit is real. Hard limits
> are only useful if you can be sure you're not DOSsing yourself.
Again, it´s the admins job to care for proper configuration.
If you´re knocking out your Email system by running jobs that
result in constant high load values, it is not a consequent
idea to ask for a change of behaviour in the software used.
> A hard limit is therefore only useful if
> there is some load value X such that
> (a) your system never exceeds X for very long without considering
> the load from e-mail, and
> (b) X is small enough so that a mail blizzard won't slow
> down everything else on your machine too severely.
>
> (a) and (b) are going to depend strongly on how you use your system,
> so you might not want to imagine that a typical system
> does only e-mail, editing and occasional compilation.
That is a questionable assumption. There are studies out there
about waste of energy by computers being idle. The figures are
impressing... so "typical" can at least not be seen as
beloning to the majority.
> I think it's a question of designing the software to be idiot-proof,
> too. Hard limits are not idiot-proof; soft limits let the software
> be misconfigured and still function. Since many of us (99.99% of
> the computer users in the world) are not exim developers, it is
> important to design software so that it can be mis-used.
What is important in this case is up to Philip, I think. In the
past, he has always tried to satisfy even the more esotherical
wishes as long as they don't hurt anyone else. I may be wrong but
it might be the majority of system administrators who clearly
vote for precise (read: hard limit) configuration.
Maybe the wishlist should be expanded with a online poll system ;-)
Regards,
vt
--
V. T. Mueller
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