Re: RE: Overhead for shell calls (RE: Scripting Additions: Embracing the Horror of Unix)
Re: RE: Overhead for shell calls (RE: Scripting Additions: Embracing the Horror of Unix)
- Subject: Re: RE: Overhead for shell calls (RE: Scripting Additions: Embracing the Horror of Unix)
- From: email@hidden
- Date: Mon, 11 Feb 2002 10:56:15 EST
Marc,
Check the numbers again. Your analysis would apply if I wanted 0.05 seconds
per shell call, but I want 0.005 seconds or better. To get that on hardware
alone I would need at least a 4 GHz DP. Pretty pricey to run a simple shell
command, and still impossible for heavy use.
But don't get me wrong. Having shell access is awesome.
Jeff Baumann
email@hidden
www.linkedresources.com
In a message dated 2/3/02 2:41:52 AM, you wrote:
>
>My testing (G4/400 OSX 10.1.2) shows that each shell call
>
>has an overhead of about 0.10 seconds.
>
>
Think about what is happening in the background:
>
+ An event is passed to the kernel, having been pushed through the OS stacks
(via
>
the L2 cache through the processor and back) from the AS environment to the
shell
>
to be excuted by the kernel (timing issues with memory content passing, not
memory
>
handler passing, probably);
>
+ a call is made for temporary (heap) memory by the shell process to store
the
>
information for the inbound instructions and the memory pointer returned to
the
>
shell process;
>
+ whatever else the kernel is doing is still going on, slicing up time at
the processor
>
and memory manager attention (having any processes running in the
background?).
>
And that's just the call...
>
>
Given all that is happening, a 1/10th of a second isn't too bad on your
particular
>
machine. Now, you said you were running G4/400 (MPC7xx0 processor, commonly
known
>
as the G4; 32Kb Data + 32kb Instruction L1 caches, and 1Mb of L2 cache
running
>
at 50% of the processor clock rate). If you went out and got yourself a
single-
>
processor 1Ghz G4, then your time per call should drop well below the .005
seconds
>
you require. Make it a dual-processor and it should fall even futher as more
of
>
the kernel's other tasks are split between processors...
>
>
Just a thought...
>
=-= Marc
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