max-connections?

[Guido Stepken]

Am Montag, 28. Mai 2001 22:22 schrieb Kurt Jagersberger:
> Hallo Liste.
>
> eine etwas seltsame Frage hab ich hier. ein mit plesk "administrierter"
> server braucht eine kleine änderung in den mysql-optionen. die maximalen
> connections sollen von 100 auf 250 hochgesetzt werden. über "mysqld
> --set-variable max_connections=200", über "mysqld -O max_connections=200"
> lässt sich die einstellung nicht ändern.
> ich hatte dann sogar versucht über phpmyadmin diese einstellung zu ändern -
> der edit-button daneben ist scheinbar nur zierde.


P.S. Hier noch ein Grund Kernel 2.2 nicht mehr zu verwenden:

If you use a lot of concurrent connections, you may suffer from a
"feature" in the 2.2 kernel that penalizes a process for forking or
cloning a child in an attempt to prevent a fork bomb attack.  This will
cause *MySQL* not to scale well as you increase the number of
concurrent clients.  On single CPU systems, we have seen this
manifested in a very slow thread creation, which means it may take a
long time to connect to *MySQL* (as long as 1 minute), and it may take
just as long to shut it down.  On multiple CPU systems, we have
observed a gradual drop in query speed as the number of clients
increases.  In the process of trying to find a solution, we have
received a kernel patch from one of our users, who claimed it made a
lot of difference for his site.  The patch is available here
(`http://www.mysql.com/Downloads/Patches/linux-fork.patch'). We have
now done rather extensive testing of this patch on both development and
production systems.  It has significantly improved `MySQL' performance
without causing any problems and we now recommend it to our users who
are still running high-load servers on 2.2 kernels.  This issue has
been fixed in the 2.4 kernel, so if you are not satisfied with the
current performance of your system, rather than patching your 2.2
kernel, it might be easier to just upgrade to 2.4, which will also give
you a nice SMP boost in addition to fixing this fairness bug.


Gru/3, Guido Stepken

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