Linus Torvalds wrote:
On Tue, 2 Oct 2007, Bill Davidsen wrote:
And yet you can make the exact same case for schedulers as security, you can
quantify the behavior, but if your only choice is A it doesn't help to know
that B is better.
You snipped a key part of the argument. Namely:
Another difference is that when it comes to schedulers, I feel like I
actually can make an informed decision. Which means that I'm perfectly
happy to just make that decision, and take the flak that I get for it. And
I do (both decide, and get flak). That's my job.
which you seem to not have read or understood (neither did apparently
anybody on slashdot).
Actually I had quoted that, made a reply, and decided that my reply was
too close to a flame and deleted the quote and the nasty reply, because
I couldn't find a nice way to say what I wanted. Oh well, I tried to
keep to a higher level, but... on this topic you seem to be off on an
ego trip. You are not the decider, George Bush is the decider, and the
only time he's not wrong he didn't understand the question. I checked
the schedule, it's not you week to be God.
There are sensible people you respect on other topics, who have the
opinion that there is room for behaviors other than CFS, and who have
created a pluggable scheduler framework which they are trying to hand
you on a platter. And you won't even consider that they might be right,
because you believe there can be one scheduler which is close to optimal
for all loads.
You say "performance" as if it had universal meaning.
Blah. Bogus and pointless argument removed.
When it comes to schedulers, "performance" *is* pretty damn well-defined,
and has effectively universal meaning.
The arguments that "servers" have a different profile than "desktop" is
pure and utter garbage, and is perpetuated by people who don't know what
they are talking about. The whole notion of "server" and "desktop"
scheduling being different is nothing but crap.
Unfortunately not so, I've been looking at schedulers since MULTICS, and
desktops since the 70s (MP/M), and networked servers since I was the
ARPAnet technical administrator at GE's Corporate R&D Center. And on
desktops response is (and should be king), while on a server, like nntp
or mail, I will happily go from 1ms to 10sec for a message to pass
through the system if only I can pass 30% more messages per hour,
because in virtually all cases transit time in that range is not an
issue. Same thing for DNS, LDAP, etc, only smaller time range. If my
goal is <10ms, I will not sacrifice capacity to do it.
I don't know who came up with it, or why people continue to feed the
insane ideas. Why do people think that servers don't care about latency?
Because people who run servers for a living, and have to live with
limited hardware capacity realize that latency isn't the only issue to
be addressed, and that the policy for degradation of latency vs.
throughput may be very different on one server than another or a desktop.
Why do people believe that desktop doesn't have multiple processors or
through-put intensive loads? Why are people continuing this *idiotic*
scheduler discussion?
Because people can't get you to understand that one size doesn't fit all
(and I doubt I've broken through).
Really - not only is the whole "desktop scheduler" argument totally bogus
to begin with (and only brought up by people who either don't know
anything about it, or who just want to argue, regardless of whether the
argumen is valid or not), quite frankly, when you say that it's the "same
issue" as with security models, you're simply FULL OF SH*T.
The real issue is that you can't imagine that people who don't share
your opinion are not only wrong but don't understand the problem. You
may be right, but when you say anyone who disagrees is wrong by
definition, then you have lost sight of productive technical
differences. When your arguments drop to personal attacks and rants it's
time to look at your technical values.
The issue with LSM is that security people simply cannot even agree on the
model. It has nothing to do with performance. It's about management, and
it's about totally different models. Have you even *looked* at the
differences between AppArmor and SELinux? Did you look at SMACK? They are
all done by people who are interested in security, but have totally
different notions of what "security" even *IS*ALL*ABOUT.
Exactly, and I'm not the only one who doubts that more than one model
would be useful. I'm sorry you can't see that about CPU schedulers as well.
In contrast, anybody who claims that the CPU scheduler doesn't know what
it's all about is just tripping. And anybody who claims that desktop
workloads are so radically different from server workloads (or that the
hardware is so different) is just totally out to lunch.
So next time, think five minutes before you start your argument.
I don't disagree with you lightly, in this case I think I have a better
superficial understanding of schedulers than you do of how production
servers are used.
--
bill davidsen <[email protected]>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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