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authorThomas Schwinge <tschwinge@gnu.org>2012-03-17 12:31:07 +0100
committerThomas Schwinge <tschwinge@gnu.org>2012-03-17 12:31:07 +0100
commit3bf27c93ac4de57623809b71517116d51465f0e1 (patch)
treeec3edc96d8a3639651e722b401bf677bc9505c68 /microkernel/viengoos
parent88ade4a03928041ad710594f3281b883528bc8ec (diff)
IRC bits.
Diffstat (limited to 'microkernel/viengoos')
-rw-r--r--microkernel/viengoos/documentation.mdwn14
-rw-r--r--microkernel/viengoos/documentation/irc_2012-02-23.mdwn159
2 files changed, 169 insertions, 4 deletions
diff --git a/microkernel/viengoos/documentation.mdwn b/microkernel/viengoos/documentation.mdwn
index 52ff7a48..edcc79a7 100644
--- a/microkernel/viengoos/documentation.mdwn
+++ b/microkernel/viengoos/documentation.mdwn
@@ -1,12 +1,12 @@
-[[!meta copyright="Copyright © 2008 Free Software Foundation, Inc."]]
+[[!meta copyright="Copyright © 2008, 2012 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
document under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no Invariant
Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
-is included in the section entitled
-[[GNU Free Documentation License|/fdl]]."]]"""]]
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
The most up-to-date documentation is in the source code itself, see in
particular the header files in the hurd directory.
@@ -17,7 +17,8 @@ version of that is available [[here|reference-guide.pdf]]. It is
not, however, automatically regenerated, and thus may not be up to
date.
-Academic Papers:
+
+# Academic Papers
* [Viengoos: A Framework for Stakeholder-Directed Resource
Allocation](http://walfield.org/papers/2009-walfield-viengoos-a-framework-for-stakeholder-directed-resource-allocation.pdf).
@@ -54,3 +55,8 @@ Academic Papers:
argue that only a small static number of scheduling policies are
needed in practice and advocate hierarchical policy specification and
central realization.
+
+
+# Miscellaneous
+
+ * [[IRC_2012-02-23]]
diff --git a/microkernel/viengoos/documentation/irc_2012-02-23.mdwn b/microkernel/viengoos/documentation/irc_2012-02-23.mdwn
new file mode 100644
index 00000000..a3229be9
--- /dev/null
+++ b/microkernel/viengoos/documentation/irc_2012-02-23.mdwn
@@ -0,0 +1,159 @@
+[[!meta copyright="Copyright © 2012 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
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+[[!meta title="IRC, freenode, #hurd, 2012-02-23"]]
+
+[[!tag open_issue_documentation open_issue_viengoos]]
+
+ <braunr> neal: i've read a bit about current modern microkernel based
+ systems, and i'm wondering
+ <braunr> neal: can a capability be used for both request and replies, or
+ does messaging need something similar to reply ports ?
+ <neal> braunr: you want a reply port
+ <neal> think about a file server:
+ <neal> the file server publishes a capability to access something
+ <neal> and multiple entities use it
+ <neal> if you wanted just bidirectional caps
+ <braunr> that's the idea i had in mind, i just wondered if it was actually
+ still the case in practice
+ <neal> you'd need to create a new capability every time you delegated the
+ cap
+ <braunr> yes
+ <braunr> thanks
+ <braunr> what about send once rights ?
+ <neal> also, if you send on a cap and then start waiting on it you could
+ get your own reply :)
+ <neal> you can get around send-once rights by using a counter
+ <braunr> no i mean, is their behaviour still needed/useful ?
+ <neal> the counter is kernel implemented
+ <neal> yes
+ <neal> as an optimization
+ <braunr> so they're just a special case of capability
+ <neal> yes
+ <braunr> not a special capability type of their own
+ <neal> but they eliminate the constant create/destroy sequence
+ <braunr> (even if it was already the case at the implementation level in
+ mach, they were named separately which could confuse people)
+ <braunr> hm
+ <braunr> actually, send once rights were used for important notifications
+ such as dead port notifications
+ <braunr> is this still handled at the kernel level in modern ukernels ?
+ <neal> in viengoos, this is called the version field
+ <neal> see chapter 2
+ <neal>
+ http://www.gnu.org/software/hurd/microkernel/viengoos/documentation/reference-guide.pdf
+ <braunr> neal: btw, congratulations for viengoos, it really is a very
+ interesting project: )
+ <neal> thanks
+ <braunr> i don't see the point of rewriting a mach clone after reading
+ about it eh
+ <neal> I would definately do the messenger concept again
+ <neal> but I'd not do persistence
+ <braunr> i don't fully understand how messengers deal with blocking
+ <neal> did you read chapter 4?
+ <braunr> i read all of it but didn't understand everything :)
+ <braunr> it's quite abstract and i didn't make time to read some of the
+ source code
+ <neal> If you have specific questions, I can try to help
+ <braunr> i'll read those chapter again and formulate my questions after
+ <neal> I may have to read them as well :)
+ <braunr> i don't understand how you manage to separate IPC from threading
+ actually
+ <braunr> are messengers queues ?
+ <neal> messengers are super-buffers
+ <neal> they contain a reference to a thread object
+ <neal> to send a message, I use a messenger
+ <neal> I put the data in a buffer
+ <neal> and then I attach the messenger to the target messenger
+ <antrik> braunr: my stance is that we should try to incorporate the ideas
+ from Viengoos into Mach in an evolutionary process...
+ <neal> this causes an activation to be sent to the target messenger's
+ thread object
+ <braunr> neal: which activation ?
+ <neal> an activation is like a CPU interrupt
+ <braunr> neal: is it "allocated" at that moment, or taken from the sending
+ thread ?
+ <braunr> (i'm not sure my question really makes sense to you :/)
+ <antrik> braunr: not sure what you are asking exactly; but the basic idea
+ is that the receiving process preallocates message buffers
+ <braunr> antrik: maybe, i'm not sure
+ <antrik> when someone sends a message, it's stored in one of these buffers,
+ and the process gets a scheduler activation, so it can decide what to do
+ with it
+ <neal> antrik is right
+ <neal> the traget messenger designates a memory buffer
+ <braunr> i'm wondering about the details of this activation
+ <braunr> is it similar to thread migration ?
+ <neal> just before the activation, the data is copied to the messenger's
+ buffer
+ <neal> now someone needs to be notified
+ <neal> (that a message arrived)
+ <neal> that someone is the thread designated in the target messenger's
+ thread field
+ <neal> this is done by an activation
+ <neal> an activation is just an upcall
+ <neal> a thread is forced to a particular IP
+ <neal> an activation isn't a "what" it's a "how"
+ <neal> I never understood thread migration
+ <neal> as it's not really about threads
+ <neal> nor it is about migration
+ <antrik> neal: what happens if another message comes in before the
+ activation handling tread is done with the previous one?...
+ <neal> the messenger is enqueued on the thread object
+ <neal> it is delivered when the thread is in normal mode
+ <neal> part of delivering an activation is putting the thread is activation
+ mode
+ <neal> when in activation mode, it can't receive any activations
+ <braunr> i see
+ <braunr> but then, when a thread receives an activation, does it handle
+ several queued messengers at once (not to loose events/messages) ?
+ <neal> (unless it does a blocking receive on a particular messenger, which
+ is necessary to support memory allocation in activated mode)
+ <neal> it handles one at a time
+ <braunr> ah right
+ <neal> it can't lose events
+ <braunr> activations are sent per messengers/events
+ <neal> well, it can
+ <neal> but it is possible to prevent this
+ <braunr> neal: also, is message passing completely atomic ?
+ <neal> I'm not sure what you mean
+ <neal> which part
+ <braunr> well, all parts of a message :)
+ <braunr> in mach, a message can contain several parts
+ <braunr> data, rights, passing one of them may fail
+ <braunr> only the header is atomically processed
+ <neal> it's not atomic in the sense that a thread can observe the data copy
+ <braunr> that's not what i meant
+ <braunr> is a message completely transferred or not at all in case of
+ failure ?
+ <neal> it may be partially transferred
+ <braunr> or can it be partially transferred
+ <braunr> ok
+ <neal> for instance, if the target thread doesn't provide a memory buffer
+ <neal> then the data can't be copied
+ <neal> I don't recall off hand how I dealt with bad addresses
+ <neal> may be it is not possible
+ <neal> I don't remember
+ <neal> sorry
+ <braunr> but if i read the message structure correctly, there can be one
+ data block, and several capability addresses in a single message, right ?
+ <neal> yes
+ <braunr> ok
+ <braunr> have you considered passing only one object (either data or
+ capability) per message ?
+ <braunr> or is it too inefficient ?
+ <neal> you at least need a reply port
+ <neal> s/port/messenger/
+ <braunr> yes but can't it be passed separately ?
+ <neal> then you have server state
+ <neal> ik
+ <braunr> hm yes
+ <braunr> thanks for your answers: )
+ <neal> no problem