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-[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]]
+[[!meta copyright="Copyright © 2011, 2013 Free Software Foundation, Inc."]]
[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
id="license" text="Permission is granted to copy, distribute and/or modify this
@@ -15,3 +15,89 @@ License|/fdl]]."]]"""]]
* [[microkernel/mach/memory_object/discussion]]
* [[resource_management_problems]]
+# IRC, freenode, #hurd, 2013-08-13
+In context of [[resource_management_problems]].
+ <braunr> and thread migration itself is something very confusing
+ <braunr> it's better to think of it as scheduling context inheritance
+ <teythoon> braunr: I read the paper I mentioned and then I wanted to find
+ the sources they modified
+ <teythoon> I failed
+ <teythoon> I hate scientific paper about software that fail to provide the
+ source code
+ <teythoon> that's not science imho b/c it's not reproducible
+ <braunr> i have some osf source code here
+ <braunr> i'll send it if you want
+ <teythoon> ah interesting
+ <braunr> but really, when you dive into it, thread migration is merely
+ scheduling context inheritance with kernel upcalls
+ <braunr> it's good
+ <teythoon> I searched for osf mach but google didn't turned up anything
+ <braunr> but it has nothing to do with resource accounting
+ <braunr> (well, it may hepl better account for cpu time actually)
+ <braunr> help*
+ <braunr> but that's all
+ <teythoon> why is that all? wouldn't that be transitive and could also be
+ used for i/o accounting?
+ <teythoon> also I tried to find alternative mach implementations
+ <teythoon> I wasn't terribly successful, and some sites are gone or
+ unmaintained for years :/
+ <braunr> we don't need that for io accountin
+ <braunr> g
+ <braunr> thread migration is a kernel property
+ <braunr> on mach with userspace drivers, io isn't
+ <braunr> mach should only control cpu and memory
+ <braunr> and you though you can account physical memory, you can't transfer
+ virtual memory accounting from one task to another
+ <teythoon> yes, but once all of those resources can be accounted to the
+ thread initiating whatever it needs doing, shouldn't that be much easier?
+ <braunr> teythoon: it's not required for that
+ <braunr> teythoon: keep in mind userspace sees activations
+ <braunr> in a thread migration enabled kernel, activations are what we
+ usually call threads, and threads are scheduling contexts
+ <teythoon> braunr: ok, so TM is not required for accounting, but surely
+ it's a good thing to have, no?
+ <braunr> teythoon: it's required for cpu accounting only
+ <braunr> which is very important :)
+ <braunr> if you look carefully, you'll see hurd servers are what use most
+ cpu
+ <braunr> there is now easy way to know which application actually uses the
+ server
+ <braunr> i personally tend to think more and more that servers *should*
+ impersonate clients
+ <braunr> TM (or rather, scheduling context inheritance) is one step
+ <braunr> it's not enough exactly because it doesn't help with resource
+ accounting
+ <braunr> teythoon:
+# IRC, freenode, #hurd, 2013-09-02
+[[!taglink open_issue_documentation]]: move information to
+ <teythoon> braunr: btw, I just noticed lot's of #ifdef MIGRATING_THREADS in
+ gnumach, so there was some work being done in that direction?
+ <braunr> gnumach is a fork of mach4
+ <braunr> at a stage whre migration was being worked on, yes
+ <teythoon> from what I've gathered, gnumach is the only surviving mach4
+ fork, right?
+ <braunr> yes
+ <braunr> well
+ <braunr> the macos x version is probably one too
+ <braunr> i don't know
+ <teythoon> oh? I read that it was based on mach3
+ <braunr> it is
+ <braunr> i can't tell how much of mach3 versus mach4 it has, and if it's
+ relevant at all
+ <teythoon> and the osfmach, was that also based on mach4?
+ <braunr> yes
+ <teythoon> ok, fair enough
+ <braunr> that's why i think macos x is based on it too
+ <braunr> i initially downloaded osfmach sources to see an example of how
+ thread migration was used from userspace
+ <braunr> and they do have a special threading library for that