Re: Cannot specify the number of threads for parsort

[Sam James]

> On 11 Feb 2023, at 01:44, Mario Roy <marioeroy@gmail.com> wrote:
> 
> > Can you explain why you need this? To me it seems odd not to use all the 
> > cores you paid for.
> 
> I was trying to simulate running on a smaller machine how long the task takes 
> for sharing with a friend. Anyway, ++ for parsort supporting the -j argument; 
> to be consistent with parallel -j. Ditto for parsort checking the PARALLEL 
> environment variable if it has -jN or -j N; this too for consistency with 
> parallel.
> 
> > There's a current phobia of having a machine actually using all it's cores 
> > and a misconception that the users can do a better job of scheduling than 
> > the scheduler!
> 
> No, not at all. Having the -j option to parsort is desirable on larger 
> NUMA-aware machines. This is true when a node is busy and wish to run on the 
> other node. Surely, one can use nodeadm or taskset. But why default to 
> spawning all those processes only for the OS to task switch more on that 
> particular node.
> 
Yeah, it's pretty normal to want to limit the number of jobs either because of 
other work one is doing on the machine, or because others are using the machine.

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