[M3devel] how to switch between user and kernel threads..

[Jay]

The installer?
I thought the granularity was at the time of linking an executable.
I personally thought a command line parameter would be reasonable.
 
 
Why not function pointers?
It is a simple straightforward method to implement.
It should add one instruction per call.
It does reduce inlinability but I'm sure we aren't getting any such such inlinability anyway.
Dynamic linking already kills inlinability, as does separate compilation of modules in most systems.
 
 
I'm not sure how the types work out in such a scheme, but probably assuming Thread.T is already a reference type, it can become ADDRESS and then loopholed to ThreadPosix.T or ThreadPThread.T.
 
 
Function pointers are also the easiest method to build. I'm not sure what the others are.
I can try making m3-libs/m3coreuserthreads that contains only m3makefiles.
Probably it can say:
LibraryName = "m3coreuserthreads"
include_dir("../m3core/m3makefile")
 
 
and m3core/m3makefile can say
if not defined("LibraryName")
  LibraryName = "m3core"
end
Library(LibraryName)
 
 
If that works, not bad.
 
 
And then cm3 or the config file can translate m3core to m3coreuserthreads at some point.
 
 
 - Jay



From: hosking at cs.purdue.eduTo: jay.krell at cornell.eduDate: Thu, 15 Jan 2009 11:31:17 +1100CC: m3devel at elegosoft.comSubject: Re: [M3devel] how to switch between user and kernel threads..
No function pointers please.  Let the installer decide whether to use native or user threads.






On 15 Jan 2009, at 08:30, Jay wrote:

I'll wait.So, build two different m3core.lib/a/so/dylib?m3core and m3coreuserthreads Compile both thread directories, if the platform supports it, andcall quake make_lib twice with slightly different parameters?An m3core specific hack in the config file or cm3?Easy enough in the config file.Very m3core specific.I suppose you could argue that quake isn't a generic build system,but it is Modula-3's build system, and that m3core is really special. The result btw, would likely be no change at all to any *.i3 or *.m3 file. I still think function pointers are the way to go.Even with function pointers, the changes to *.i3 and *.m3 would be very minor.Just the export list would vary.And new *.i3 files introduced.  - Jay

From: hosking at cs.purdue.eduTo: jay.krell at cornell.eduDate: Wed, 14 Jan 2009 21:31:22 +1100CC: m3devel at elegosoft.comSubject: Re: [M3devel] how to switch between user and kernel threads..I don't want dynamic switching.  A link-time switch is just fine.

Also, please don't go messing about with this right now -- I have changes pending for the threads system that will be harder to integrate if you change with it further.





On 14 Jan 2009, at 20:14, Jay wrote:

Are people really against using function pointers for this?Either changing the interface to have function pointer variables (I'm not sure Modula-3 allows this, but in C you can fairly transparently replace functions with function pointers; client code just keeps working; it breaks down in C++ with overloading), or having a set of functions that just call/jump through function pointers? There would be no if, no conditional branches. Dynamic linking on Windows always goes through function pointers already. So while yes it adds another instruction, it is already never getting inlined.Don't other platforms do that too?Or they patch every call site? I'm not sure otherwise of a simple method.Easiest might be to have a parallel directory structure to m3core, with just m3core files.That would wastefully rebuild all of m3core a second time, for just a small amount of variation. I think function pointers are the way to go here.  - Jay
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