[Toybox] Bad idea regarding threading...

[Elie De Brauwer]

On Mon, Apr 30, 2012 at 9:39 AM, David Seikel <onefang at gmail.com> wrote:
> On Mon, 30 Apr 2012 09:25:37 +0200 Elie De Brauwer
> <eliedebrauwer at gmail.com> wrote:
>
>> On Sun, Apr 29, 2012 at 2:57 AM, Rob Landley <rob at landley.net> wrote:
>> > It occurs to me that if I add a CONFIG_TOYBOX_THREADS with the new
>> > directory traversal infrastructure, things like cp -a and rm -r
>> > could be done in a multithreaded manner.
>> >
>> > I.E. create a thread pool equal to the number of processors, and
>> > then every time you encounter a directory hand off the callbacks to
>> > a thread out of the thread pool. Everything they're doing is
>> > openat() based on a filehandle stored in the node structure (or a
>> > filehandle pair with the second stored in the node's ->extra
>> > field), so you don't need to worry about the current directory
>> > changing in another thread...
>>
>> Indeed, and I think that this could also be a very nice feature to
>> differentiate toybox from similar tools, to my knowledge there aren't
>> any 'userlands' availble which have inherent multithreading support
>> (typically because most stem from the time that it was easier to
>> purchase a human kidney than to purchase smp systems.
>> The only thing I want to add there is that in such a scenario I expect
>> the number of usable cores to be runtime configurable (e.g. through an
>> environment variable).
>
> Um, I would hope that the code figures out for itself how many cores
> are available.  Perhaps you meant artificially limiting cores, to keep
> some in reserve for something else?
>

Indeed, when I have some cores dedicated to chewing some data, I don't
want some recursive chmod which some **** typed into a prompt to flood
the scheduler. So selecting the number of cores automatically is good,
but allowing an override is better. And when you use magic such as
isolcpus ( http://www.kernel.org/doc/Documentation/kernel-parameters.txt
) whilst  the number of cores is automatically selected, this will
just result in a whole bunch of blocked threads. Anyhow, imho that all
is.

E.

-- 
Elie De Brauwer

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