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How Well Do Most OSes Handle Resource Management?

Posted by Cliff on from the running-a-tight-and-efficient-system dept.

schlika asks: "After getting some troubles with a highly loaded Web server running Linux 2.2.12 I read some infos about its max thread/processes limitation and 'not-so-great' virtual memory management. Could some of you comment such issues with other OS's such as FreeBSD (which everyone says it's better for that task without ever giving explanations), OpenBSD, NetBSD, Solaris, Linux2.4 and others? Please give real world examples/comparisons if possible."

1 of 10 comments (clear)

  1. Unix by sql*kitten · · Score: 4
    The answer is (and this is a bit of a rant) that almost all Unix implementations handle resources terribly.

    Unix allocates CPU time clumsily, nice and pbind are about as much control as a sysadmin has over a running process, other than stopping it altogether and restarting it. Contrast this with OS/390 or VMS where the sysadmin can control exactly how much CPU a process gets, the size of its working set, migrate processes around between nodes in a cluster. IBM have a tool called the "Work Load Manager". It is able to configure your system based on what you want to do, not how you want to do it. For example, you say that this batch job must complete by this time in the morning, this class of transaction must complete within this time, and this group of users get mo more than 10% of CPU in the morning, and 30% in the afternoons, and WLM will configure your cluster, if it is physically possible, to do it. You can run a mainframe class OS at 90% of the machines capability consistently, a Unix system rarely exceeds 30% of its capacity when averaged over a period of time, it simply spends too much time either waiting for things or trying to manage its own workload. And what's worse, the CPU gets involved in every I/O in a Unix system, because of the way buffers work. Every disk block gets transferred by a CPU through an operating system buffer. When you edit on a UNIX box, every single character goes to the CPU and gets echoed back. And on the network, even character gets a packet sent back and forth. VMS deals with "record" - whole lines of text, even at the network protocol level.

    And don't even get me started on the lost+found directory. You don't get that on an industrial grade file system, because it's journalled to ensure consistency.

    Thankyou for listening.