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%%CreationDate: 14 August 1990 11:32
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%%EndProlog
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15 /Helvetica-Bold AF
22678 14054 MT
(The Mach cpu_server:)SH
15217 15963 MT
(An Implementation of Processor Allocation)SH
10 /Helvetica AF
27543 20922 MT
(David L.Black)SH
23180 23774 MT
(Department of Computer Science)SH
24599 25200 MT
(Carnegie-Mellon University)SH
25875 26626 MT
(Pittsburgh, PA 15213)SH
/Helvetica-Bold SF
27988 28052 MT
(Version of:)SH
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27097 29478 MT
(14 August 1990)SH
13 /Helvetica-Bold AF
27963 46816 MT
(Abstract)SH
10 /Helvetica AF
7200 49349 MT
(The CPU-Server is a user-mode server that)
9 W( performs processor allocation for the Mach operating system.)8 W
7200 50492 MT
(This document describes the server and it's user interfaces.)SH
8312 61929 MT
(This research was sponsored by the Defense)
199 W( Advanced Research Projects Agency \050DOD\051, ARPA)200 W
7200 63072 MT
(Order No. 4864, monitored by the Space and)
347 W( Naval Warfare Systems Command under contract)346 W
7200 64215 MT
(N00039-84-C-0467.)SH
8312 66499 MT
(The views and conclusions contained in this document are those of the authors and should)
156 W( not be)157 W
7200 67642 MT
(interpreted as)
316 W( representing official policies, either expressed or implied, of the Defense Advanced)315 W
7200 68785 MT
(Research Projects Agency or of the U.S.  Government.)SH
ES
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(1)SH
12 SS 
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(1. Introduction)SH
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(This document describes the cpu_server, a user-mode server that performs)
SH( processor allocation for the)1 W
7200 10927 MT
(Mach operating system, and)
29 W( its library interfaces.  The server implements processor allocation policy; the)28 W
7200 12353 MT
(actual mechanisms are contained in the Mach kernel \050see related document\051.)
37 W( The)
353 W( library interfaces hide)38 W
7200 13779 MT
(the details of server interaction)
53 W( from applications with simple scheduling requirements.  This server is an)52 W
7200 15205 MT
(example implementation of processor allocation policy; many)
4 W( other policies can be implemented using the)5 W
7200 16631 MT
(mechanisms provided by the kernel.)SH
8312 19198 MT
(Not all releases of Mach)
15 W( support this server. It is mainly interesting on multi-processor machines, so no)14 W
7200 20624 MT
(major effort has been made to support it on)
76 W( the standard uni-processor versions of Mach. However, the)77 W
7200 22050 MT
(new releases of Mach support it on all machines. On systems that support it, this software \050MiG)
33 W( interface)32 W
7200 23476 MT
(to server and library interfaces\051 is available in the cpu library \050/usr/mach/lib/libcpu.a, -lcpu command to ld\051.)SH
12 /Helvetica-Bold AF
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(2. Concepts)SH
10 /Helvetica AF
8312 28657 MT
(The server performs processor)
145 W( allocation by assigning processors to processor sets provided by its)146 W
7200 30083 MT
(clients. This)
362 W( allows the clients to use and manage the processors without giving clients)
42 W( complete control)41 W
7200 31509 MT
(over them; only the server)
62 W( has the port capabilities required to reassign processors.  Processor sets are)63 W
7200 32935 MT
(entities exported by)
64 W( the Mach kernel; threads assigned to a processor set run exclusively on processors)63 W
8 SS 
37325 34010 MT
(tm)SH
10 SS 
7200 34361 MT
(assigned to that set and vice versa \050with the exception of some Unix)SH
38491 XM
(system calls\051.)SH
8312 36928 MT
(The server interface is designed around a class of objects)
78 W( called requests.  A request consists of the)79 W
7200 38354 MT
(following components:)SH
/Symbol SF
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(\267)SH
/Helvetica SF
9980 XM
(A run duration,)SH
/Symbol SF
9242 41641 MT
(\267)SH
/Helvetica SF
9980 XM
(A sequence of <processor set, number of processor> pairs.)SH
7200 43067 MT
(A request is satisfied by assigning each processor set its corresponding number of processors for the run)21 W
7200 44493 MT
(duration specified.  The server enforces)
10 W( internal limits on the number of processors and the maximum run)11 W
7200 45919 MT
(time. Current)
278 W( limits are 15 minutes and 75% or less of the processors on the system.)SH
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(3. Implementation)SH
10 /Helvetica AF
8312 51100 MT
(The server satisfies requests in a greedy fashion with strict adherence to)
92 W( the order in which they are)91 W
7200 52526 MT
(received. For)
326 W( example,)
24 W( if the server has 10 processors and receives requests for 4, 7, and 2 processors,)25 W
7200 53952 MT
(it will satisfy the request for 4 first, and then the requests for 7 and 2 together.  This algorithm was)
8 W( chosen)7 W
7200 55378 MT
(for its simplicity and lack of starvation; more)
285 W( sophisticated algorithms that make better use of the)286 W
7200 56804 MT
(processors by satisfying requests out of order could be used.)SH
8312 59371 MT
(The server implementation was based on the cthreads library and the Mach Interface Generator\050MiG\051.)43 W
7200 60797 MT
(Two threads are used internally; one manages the assignment of processors)
226 W( to requests, the other)227 W
7200 62223 MT
(manages all interactions with clients.)
232 W( Clients)
741 W( communicate with the server via rpcs; MiG-generated)231 W
7200 63649 MT
(interfaces hide the details of the message formats.  In addition the server can optionally generate)263 W
7200 65075 MT
(notification messages to)
100 W( indicate that processors have been allocated to a request and that processors)99 W
7200 66501 MT
(are about to be removed from a request; these messages can)
142 W( be used for internal synchronization of)143 W
7200 67927 MT
(applications that require multiple processors for proper execution.)SH
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(2)SH
12 SS 
7200 8075 MT
(4. Interface)SH
10 /Helvetica AF
8312 9501 MT
(The server's interface to its clients uses remote procedure calls to implement the following primitives:)SH
/Symbol SF
9242 10973 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(cpu_request_create)SH
/Helvetica SF
(\050server, total_processors, run_time, *delay, *request\051)
509 W( -- create a)508 W
9980 12116 MT
(request for)180 W
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15398 XM
(total_processors)SH
/Helvetica SF
23192 XM
(processors for)180 W
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30165 XM
(run_time)SH
/Helvetica SF
34514 XM
(seconds. The)
640 W( request object and a)181 W
9980 13259 MT
(delay estimate are returned.)
149 W( The)
575 W( initial server port \050)148 W
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(server)SH
/Helvetica SF
(\051 is obtained by looking up the)148 W
9980 14402 MT
(name "cpu_server" with the local name service.)SH
/Symbol SF
9242 16217 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(cpu_request_add)SH
/Helvetica SF
(\050request, processor_set, processors, *processors_left\051 --)
262 W( Add the tuple)263 W
9980 17360 MT
(<)SH
/Helvetica-Oblique SF
(processor_set)SH
/Helvetica SF
(,)SH
/Helvetica-Oblique SF
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(processors)SH
/Helvetica SF
(> to the specified request.)
253 W( Return)
783 W( the number of processor)252 W
9980 18503 MT
(remaining in the request \050i.e. that can be used in future)SH
/Helvetica-Bold SF
34493 XM
(cpu_request_add)SH
/Helvetica SF
43051 XM
(calls\051.)SH
/Symbol SF
9242 20318 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(cpu_request_set_notify)SH
/Helvetica SF
(\050request, notify_port\051 - Ask the server to send a notification)451 W
9980 21461 MT
(message to)43 W
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(notify_port)SH
/Helvetica SF
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(after the processors are allocated)
43 W( and 1 second before removing the)42 W
9980 22604 MT
(processors. Applications)
714 W( that receive these messages can use them to make sure that)218 W
9980 23747 MT
(execution only takes place while all of the processors are allocated;)
15 W( the end message can be)14 W
9980 24890 MT
(used to initiate a barrier synchronization to stop cleanly, and the start message can be used)48 W
9980 26033 MT
(to exit the barrier.)SH
/Symbol SF
9242 27848 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(cpu_request_activate)SH
/Helvetica SF
(\050request, options, total_time,)
376 W( *delay\051 -- Activate the request \050i.e.)375 W
9980 28991 MT
(request the server to)
155 W( satisfy it\051.  A maximum delay until the requested processors will be)156 W
9980 30134 MT
(allocated is returned.  No further)52 W
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24854 XM
(cpu_request_add)SH
/Helvetica SF
33464 XM
(calls are permitted)
52 W( on the request.  The)51 W
9980 31277 MT
(following options are supported:)SH
7 /Symbol AF
12160 32528 MT
(\267)SH
10 /Helvetica AF
12760 32678 MT
(Destroy - Destroy the processor)
39 W( sets when the request is completed.  This is intended)40 W
3445 50 12760 32878 UL
12760 33821 MT
(to support naive users by)
116 W( preventing a program that overruns its request from going)115 W
12760 34964 MT
(into suspended animation; destroying)
80 W( its processor sets forces the program back into)81 W
12760 36107 MT
(the default processor set where it will continue to run.)SH
7 /Symbol AF
12160 37772 MT
(\267)SH
10 /Helvetica AF
12760 37922 MT
(Repeat - Repeat the request for)52 W
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27413 XM
(total_time)SH
/Helvetica SF
(. The)
382 W( time)
52 W( for each instance of the request)51 W
3224 50 12760 38122 UL
12760 39065 MT
(is specified by the run_time argument of the)294 W
/Helvetica-Bold SF
34789 XM
(cpu_request_create)SH
/Helvetica SF
44810 XM
(operation that)295 W
12760 40208 MT
(created the request.)SH
/Symbol SF
9242 42023 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(cpu_request_activate_task)SH
/Helvetica SF
(\050request, options, total_time, task, *delay\051 --)
572 W( Identical to)571 W
/Helvetica-Bold SF
9980 43166 MT
(cpu_request_activate)SH
/Helvetica SF
(, but informs the server that the application using the processor sets is)SH
9980 44309 MT
(a task; this allows the server to optimize assignment and removal of processors by using)151 W
/Helvetica-Bold SF
9980 45452 MT
(task_suspend)SH
/Helvetica SF
16978 XM
(and)SH
/Helvetica-Bold SF
18975 XM
(task_resume)SH
/Helvetica SF
25418 XM
(-- processor assignment is much faster if the)
51 W( processor is)52 W
9980 46595 MT
(idle.)SH
/Symbol SF
9242 48410 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(cpu_request_destroy)SH
/Helvetica SF
(\050request\051 - Destroy the)
75 W( specified request, freeing any processors that)74 W
9980 49553 MT
(were allocated to it.  If the Notify end option)
61 W( applies, an end notification will be sent and the)62 W
2556 50 22080 49753 UL
1668 50 24975 49753 UL
9980 50696 MT
(freeing of the processors will be delayed by 1 second.)SH
/Symbol SF
9242 52511 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(cpu_request_status)SH
/Helvetica SF
(\050request, *reserved_processors,)
1206 W( *assigned_processors, *active,)1205 W
9980 53654 MT
(*options, *time\051 - Find out information about a request including whether it has processors)124 W
9980 54797 MT
(assigned to it, and how long until the assigned)
45 W( processors will be removed, or the maximum)44 W
9980 55940 MT
(delay until processors will be assigned to it.)SH
/Symbol SF
9242 57755 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(cpu_server_info)SH
/Helvetica SF
(\050server, *max_time, *max_total_time, *max_processors, *delay\051 -- Obtain)214 W
9980 58898 MT
(information about the server.)310 W
/Helvetica-Oblique SF
24814 XM
(max_time)SH
/Helvetica SF
29736 XM
(is the maximum time for a single)
310 W( request in)309 W
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9980 60041 MT
(cpu_request_create)SH
/Helvetica SF
(.)SH
/Helvetica-Oblique SF
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(max_total_time)SH
/Helvetica SF
27926 XM
(is the maximum total time for)
202 W( a repeating request)203 W
9980 61184 MT
(created by the Repeat option to)285 W
/Helvetica-Bold SF
25920 XM
(cpu_request_activate)SH
/Helvetica SF
36708 XM
(or)SH
/Helvetica-Bold SF
38159 XM
(cpu_request_activate_task)SH
/Helvetica SF
(.)SH
3224 50 17450 61384 UL
/Helvetica-Oblique SF
9980 62327 MT
(max_processors)SH
/Helvetica SF
17625 XM
(is the maximum number of processors for any request.)32 W
/Helvetica-Oblique SF
42676 XM
(delay)SH
/Helvetica SF
45376 XM
(is the current)32 W
9980 63470 MT
(maximum delay until a new request can be satisfied.  The)49 W
/Helvetica-Bold SF
36252 XM
(cpuinfo)SH
/Helvetica SF
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(program uses)
49 W( this call to)48 W
9980 64613 MT
(determine if the cpu_server is available and what its current situation is.)SH
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(3)SH
12 SS 
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(5. Library Interfaces)SH
10 /Helvetica AF
8312 9501 MT
(The above server interface along with the kernel interface will be used directly by programs)
7 W( that require)8 W
7200 10927 MT
(explicit control over which threads are executing on which processors at which time.)
4 W( For)
285 W( applications with)3 W
7200 12353 MT
(less stringent processor allocation requirements, simple library interfaces which hide all of the)
150 W( internal)151 W
7200 13779 MT
(details of interaction with the kernel and)
323 W( server may be appropriate.  Four interfaces have been)322 W
7200 15205 MT
(developed, the allocate, task, hook, and task-hook interfaces.)SH
3446 50 14038 15405 UL
1834 50 18040 15405 UL
2168 50 20430 15405 UL
4335 50 25100 15405 UL
8312 17772 MT
(The allocate interface supports a)
45 W( single allocation of a pool of processors.  It exports the following two)46 W
3446 50 10358 17972 UL
7200 19198 MT
(calls:)SH
/Symbol SF
9242 20670 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(allocate_processors)SH
/Helvetica SF
(\050num_processors, time, interactive\051 - Allocate)768 W
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43829 XM
(num_processors)SH
/Helvetica SF
9980 21813 MT
(processors for)
48 W( the specified time.  If the time is larger than the server's maximum slice time,)49 W
9980 22956 MT
(then a repeating request is)
82 W( automatically submitted.  If)81 W
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(interactive)SH
/Helvetica SF
39863 XM
(is TRUE, errors generate)81 W
9980 24099 MT
(printfs, and the user is asked whether the)
316 W( server's maximum delay is acceptable; no)317 W
9980 25242 MT
(allocation is performed if the answer is no.)SH
/Symbol SF
9242 27057 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(deallocate_processors)SH
/Helvetica SF
(\050\051 - Free the processors)
186 W( allocated by)185 W
/Helvetica-Bold SF
38456 XM
(allocate_processors)SH
/Helvetica SF
(. This)648 W
9980 28200 MT
(must be called by a thread in the same task as the thread that did the allocation.)SH
/Helvetica-Bold SF
7200 29626 MT
(allocate_processors)SH
/Helvetica SF
17474 XM
(does not return until the allocation of processors has started; it performs a)325 W
/Helvetica-Bold SF
7200 31052 MT
(task_assign)SH
/Helvetica SF
13240 XM
(internally so that the initial thread and all threads and tasks subsequently created share)
37 W( the)36 W
7200 32478 MT
(allocated processors.  If a program)
267 W( overruns its time allocation, it will continue to run, but without)268 W
7200 33904 MT
(dedicated processors.)SH
8312 36471 MT
(The task interface is identical to the allocate interface, but is restricted to applications)
94 W( consisting of a)93 W
1834 50 10407 36671 UL
7200 37897 MT
(single task so that the server can exploit efficiencies available in this case)
104 W( \050suspending the task before)105 W
7200 39323 MT
(removing processors\051.)
5 W( The)
287 W( server will perform its own)4 W
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31521 XM
(task_suspend)SH
/Helvetica SF
38472 XM
(and)SH
/Helvetica-Bold SF
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(task_resume)SH
/Helvetica SF
46818 XM
(calls on the task)4 W
7200 40749 MT
(in this case.  The task interface exports the following two calls:)SH
/Symbol SF
9242 42221 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(task_allocate_processors)SH
/Helvetica SF
(\050num_processors, num_seconds, interactive\051 - Identical)
667 W( to)668 W
/Helvetica-Bold SF
9980 43364 MT
(allocate_processors)SH
/Helvetica SF
(, but also promises the server)
371 W( that all or the threads using the)370 W
9980 44507 MT
(processors will be in the current task.)SH
/Symbol SF
9242 46322 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(task_deallocate_processors)SH
/Helvetica SF
(\050\051 - Deallocate the processors)
1519 W( allocated by)1520 W
/Helvetica-Bold SF
9980 47465 MT
(task_allocate_processors)SH
/Helvetica SF
(.)SH
8312 50032 MT
(The hook interface supports allocation of a pool of processors,)
56 W( with user scheduling hooks.  It exports)55 W
2168 50 10369 50232 UL
7200 51458 MT
(the following two calls:)SH
/Symbol SF
9242 52930 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(allocate_processors_with_hooks)SH
/Helvetica SF
(\050num_processors, num_seconds, start_hook,)
185 W( end_hook,)186 W
9980 54073 MT
(interactive\051 - Allocate the specified number of processors for the specified number)
329 W( of)328 W
9980 55216 MT
(seconds. If)
730 W( the number of seconds is greater than the server's maximum slice)
226 W( time, a)227 W
9980 56359 MT
(repeating request is automatically submitted.)315 W
/Helvetica-Oblique SF
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(start_hook)SH
/Helvetica SF
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(is called each time after)
315 W( the)314 W
9980 57502 MT
(processors are allocated.  Similarly,)88 W
/Helvetica-Oblique SF
26480 XM
(end_hook)SH
/Helvetica SF
31238 XM
(is called approximately 1 second before)
88 W( any)89 W
9980 58645 MT
(processor deallocation.)SH
/Helvetica-Oblique SF
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(interactive)SH
/Helvetica SF
25653 XM
(functions identically to the previous interfaces.)SH
/Symbol SF
9242 60460 MT
(\267)SH
/Helvetica-Bold SF
9980 XM
(deallocate_processors_with_hooks)SH
/Helvetica SF
(\050\051 - Free the processors)
1381 W( allocated by)1380 W
/Helvetica-Bold SF
9980 61603 MT
(allocate_processors_with_hooks)SH
/Helvetica SF
(. The)530 W
/Helvetica-Oblique SF
28921 XM
(end_hook)SH
/Helvetica SF
33717 XM
(will not be called, but users)
126 W( should be)127 W
9980 62746 MT
(aware of the race between this deallocate call and the server ending a time slice.)SH
7200 64172 MT
(A thread must be dedicated to the)8 W
/Helvetica-Bold SF
22543 XM
(allocate_processors_with_hooks)SH
/Helvetica SF
38557 XM
(call; i.e. the calling thread)
8 W( does not)7 W
7200 65598 MT
(return until the allocation request is finished)
180 W( or terminated.  This dedicated thread is assigned to the)181 W
7200 67024 MT
(allocated processors \050this can)
29 W( be reversed by performing a)28 W
/Helvetica-Bold SF
33743 XM
(thread_assign_default)SH
/Helvetica SF
44663 XM
(or)SH
/Helvetica-Bold SF
45858 XM
(thread_assign)SH
/Helvetica SF
52944 XM
(as)SH
7200 68450 MT
(part of the first invocation of)101 W
/Helvetica-Oblique SF
20368 XM
(start_hook)SH
/Helvetica SF
(. All)
480 W( threads within its)
101 W( task and subsequently created tasks are)102 W
7200 69876 MT
(also assigned \050c.f.)SH
/Helvetica-Bold SF
15537 XM
(task_assign)SH
/Helvetica SF
(\051. Both)278 W
/Helvetica-Oblique SF
24764 XM
(start_hook)SH
/Helvetica SF
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(and)SH
/Helvetica-Oblique SF
31657 XM
(end_hook)SH
/Helvetica SF
36327 XM
(must return.)SH
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(Finally, there is the task-hook interface, which combines the functionality of the hook)
41 W( interface with the)40 W
4335 50 17146 8129 UL
7200 9355 MT
(server optimization of the task interface; the calls in this interface are the hook interface calls with)
72 W( task_)73 W
7200 10781 MT
(prefixed. Users)
308 W( should note that the interfaces are independent; processors must)
15 W( be deallocated with the)14 W
7200 12207 MT
(deallocate call from the same interface that was used to allocate them.)SH
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(6. Extensions)SH
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(The cpu_server could be extended in a number of ways:)SH
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(Time Sensitivity - Allow more of the machine to be allocated during off peak periods.)SH
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(\267)SH
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(Request Size Sensitivity - Use)
179 W( a declining priority system instead of absolute ordering to)180 W
9980 21818 MT
(speed throughput.  This is a standard technique from schedulers for)
292 W( physical memory)291 W
9980 22961 MT
(machines; other similar techniques are also applicable \050the current processor allocation)267 W
9980 24104 MT
(problem for multiprocessors is essentially similar to the memory)
299 W( allocation problem for)298 W
9980 25247 MT
(schedulers for physical memory machines\051.)SH
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(\267)SH
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(User Sensitivity)
384 W( - Reserve some portion of the machine for certain users based on)385 W
9980 28205 MT
(administrative decisions \050e.g.)
206 W( they paid for some portion of the machine, so they should)205 W
9980 29348 MT
(always be able to get at least that portion\051.)SH
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(\267)SH
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(Non-Uniform Topologies)
15 W( - For NUMA \050Non Uniform Memory Access\051, all topology knowledge)16 W
9980 32306 MT
(and policy is located in the server.)
11 W( Techniques)
299 W( such as first-fit and best-fit may be applicable)10 W
9980 33449 MT
(to the processor)
89 W( allocation server for such a machine \050e.g. the clustered Gigamax machine)90 W
9980 34592 MT
(being built by Encore\051.)SH
7200 36018 MT
(In addition the server and the)
84 W( kernel interface \050thread assignment\051 could be used directly in a language)83 W
7200 37444 MT
(runtime that is sophisticated enough to control and allocate processors to its threads.)SH
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(Table of Contents)SH
11 SS 
9036 9319 MT
(1. Introduction)SH
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(1)SH
9036 10563 MT
(2. Concepts)SH
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(1)SH
9036 11807 MT
(3. Implementation)SH
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(1)SH
9036 13051 MT
(4. Interface)SH
53388 XM
(2)SH
9036 14295 MT
(5. Library Interfaces)SH
53388 XM
(3)SH
9036 15539 MT
(6. Extensions)SH
53388 XM
(4)SH
ES
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