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+[[!meta copyright="Copyright © 2010, 2011, 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]]."]]"""]]
+
+[[!tag open_issue_hurd]]
+
+Hurd servers / VFS libraries are multithreaded.
+
+
+# Implementation
+
+  * well-known threading libraries
+
+      * [[hurd/libthreads]]
+
+      * [[hurd/libpthread]]
+
+
+# Design
+
+See [[hurd/libports]]: roughly using one thread per
+incoming request.  This is not the best approach: it doesn't really make sense
+to scale the number of worker threads with the number of incoming requests, but
+instead they should be scaled according to the backends' characteristics.
+
+The [[hurd/Critique]] should have some more on this.
+
+[*Event-based Concurrency
+Control*](http://soft.vub.ac.be/~tvcutsem/talks/presentations/T37_nobackground.pdf),
+Tom Van Cutsem, 2009.
+
+
+## IRC, freenode, #hurd, 2012-07-08
+
+    <youpi> braunr: about limiting number of threads, IIRC the problem is that
+      for some threads, completing their work means triggering some action in
+      the server itself, and waiting for it (with, unfortunately, some lock
+      held), which never terminates when we can't create new threads any more
+    <braunr> youpi: the number of threads should be limited, but not globally
+      by libports
+    <braunr> pagers should throttle their writeback requests
+    <youpi> right
+
+
+# Alternative approaches:
+
+  * <http://www.concurrencykit.org/>
+
+  * Continuation-passing style
+
+      * [[microkernel/Mach]] internally [[uses
+        continuations|microkernel/mach/continuation]], too.
+
+  * [[Erlang-style_parallelism]]
+
+      * [[!wikipedia Actor_model]]; also see overlap with
+        {{$capability#wikipedia_object-capability_model}}.
+
+  * [libtcr - Threaded Coroutine Library](http://oss.linbit.com/libtcr/)
+
+  * <http://monkey.org/~provos/libevent/>
+
+---
+
+See also: [[multiprocessing]].