Jim Helm [EMAIL PROTECTED] wrote:
Everything I've read as an SA (for Solaris at least - though I would
expect the other *nices to be similar) was to never set a user space
(non O/S) process to less than -15. Other than that, it's another of
those YMMV, measure before and after, and if it helps great. Trying to
second guess process schedulers is a tricky business though, and you
really need to intimately know how your system behaves before trying it.
-Original Message-
Alexey Zvyagin has suggested a use of Unix process priorities
to improve
the performance of the web services during the peak hours:
Alex writes:
-
[snip]
The CPU priorities help to handle an increased traffic on the
overloaded
server.
-
I think the key here is the fact that the system is
overloaded/overcommitted. Too many processes are competeing for
CPU.
Putting my SA hat on, I would say the processes need to be split
across multiple pieces of hardware or a new machine needs to replace
the current system. That's the only real long-term solution for a
system in this state.
The priorities as described help set a relative importance between
the processes--the front-end is more important than the database with
the larger server processes in the middle. This is not
unreasonable. But a serious solution to the problem of an overloaded
system is to put in more system. The priorities might be helpful for
the few minutes/hours/days needed to get the new hardware on the
floor.
Imho, a web server should be designed for the expected peak normal
usage plus a fudge factor thrown in for safety and multiplied by a
small integer greater than one for growth (I'm optimistic).
Conclusion of my thoughts: putting in a blurb about priorities being
able to set relative importance of processes is fine, but don't cast
it as a solution (just as swap space is not a solution to constrained
memory). It's a bit of a band-aid that can help until the problem
can be fixed.
--
James Smith [EMAIL PROTECTED], 979-862-3725
Texas AM CIS Operating Systems Group, Unix
