Re: tux on 2.4.27 kernel and referrer checking

[William Lovaton <williama_lovaton@coomeva.com.co>]

El jue, 28-10-2004 a las 17:37, Marek Habersack escribió:
> > I haven't use FC2 in desktops that much but I love what I see, feature
> > wise and stability wise.  In fact, I'm dying to use FC3 in my
> > workstation (home and office) ASAP.
> I cannot be a partner for discussion here since I don't use any of the
> RedHat systems anymore, but I do think it's not a good idea to use the same
> kernel for both desktop and server (think about the i/o scheduler for
> instance, or the filesystems you use).

Agree, but the new process scheduler is a lot smarter and it does a
really good job.

> > 
> > > As for 2.4, it has serious problems with
> > > the VM under stress (heavy webserver load with php/sql activity) to the
> > > point when an OOM kills not only the process(es) but also the machine.
> > 
> > OOM?? May be you have some serious issues with your lack of memory or
> > software leaking a lot.
> Unlikely. Even then, a user application should NOT be able to kill the
> kernel. What we see is the treaded 0 order allocation failed, apache
> (because it's apache in 99% of case) gets killed and the kernel freezes. No
> oops, nothing in the logs. It's not a unit issue, it happened on several
> machines (ranging from P3 to P4 systems) with at least 0.5G of RAM and twice
> as much of swap.

AFAICT, your problem is lack of RAM.  Our system is limited to 340
processes with 2GB of RAM.  It use the whole RAM, with about 800MB of
cache so it never swaps.  If you start to swap, then you need more RAM
(or fix the programs).

Whit tux it is well under 100 processes and 600MB of RAM.


> > In my case high load means 115 requests/sec according to apache
> > access_log 70% of them are static content, the rest is dynamic (PHP).  I
> > have seen peaks of 320 req/sec.  This is why TUX is so great.
> > 
> > The load average is between 40 and 80 during peak times without tux. 
> > The server gets 4.5 millions of requests per day.
> Some of our machines all of a sudden get load average over 300, one of them
> had load of over 900 last week. Surely, most of the cases can be attributed
> to bad programming (php, perl scripts that do weird things), but that should
> not crash the kernel. At least I hope so. We tried resource limits, but on a
> reasonably busy machine it's rather hard to come up with sensible resource
> limits for over 800 apache processes. If you give each of them 1/3 of the
> RAM to use as the maximum, it's enough that 6 of them run away and the
> machine dies. They are dedicated severs handling an awful lot of traffic, so
> limiting the number of apache processes below 512 makes no real sense.
> vservers might be a good promise for enforcing resource limits perhaps, but
> that only with 2.6, so not for us yet.

Mmmm... load avg of 300, 800... that's insane.  You just need a bigger
CPU this is just a matter of MHz.  With such a load you can't even type
on a terminal.

800 load avg means that there are 800 processes waiting to be run, but
they are not running because the CPU is taken by another process.  The
processes are just fighting to get a little slice of CPU.

And 800 processes?? How much RAM do you have? what are the technical
specs of the server?

BTW, if you upgrade the CPU you will need less RAM.

> 
> > > > The only problem I have is TUX (not using it right now) and that's why
> > > > I'm subscribed to this list.  Anyway TUX is not present in the official
> > > > kernel anymore.
> > > What is the problem with TUX?
> > 
> > http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=125091
> Sounds as awful as the bug Ingo fixed sometime ago for us - but we had a
> problem with the user space modules for Tux.

It should be fixed by now (I hope) but I can't test it right now because
the updated kernel is for the new FC3.  So I just have to wait for the
appropiate update for FC2.


-William