7 Nokia Corporation - initial contribution. |
7 Nokia Corporation - initial contribution. |
8 Contributors: |
8 Contributors: |
9 --> |
9 --> |
10 <!DOCTYPE concept |
10 <!DOCTYPE concept |
11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
12 <concept id="GUID-7B173E02-9697-51F4-A7E8-795AEF547109" xml:lang="en"><title>Thread |
12 <concept id="GUID-7B173E02-9697-51F4-A7E8-795AEF547109" xml:lang="en"><title>Thread Priority Scheme</title><shortdesc>Explains the factors involved in allocating thread priority.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
13 Priority Scheme</title><shortdesc>Explains the factors involved in allocating thread priority.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
13 <p>At any given time, the thread running on Symbian platform is the |
14 <p>At any given time, the thread running on Symbian platform is the one with |
14 one with the highest priority that is ready to run. The priority of |
15 the highest priority that is ready to run. The priority of a thread is simply |
15 a thread is simply a number; the value determines the priority; the |
16 a number; the value determines the priority; the greater the number, the higher |
16 greater the number, the higher the priority. We call this the <i>true</i> or <i>absolute</i> priority of the thread. </p> |
17 the priority. We call this the <i>true</i> or <i>absolute</i> priority of |
17 <p>The Kernel schedules a fixed amount of time called a <i>quantum</i> for a thread to run on the CPU, and the scheduler chooses the highest |
18 the thread. </p> |
18 priority thread that is ready to run. Threads of equal priority are |
19 <p>The Kernel schedules a fixed amount of time called a <i>quantum</i> for |
19 executed on a <i>round robin basis</i>. </p> |
20 a thread to run on the CPU, and the scheduler chooses the highest priority |
|
21 thread that is ready to run. Threads of equal priority are executed on a <i>round |
|
22 robin basis</i>. </p> |
|
23 <p>The <i>true</i> priority values range from 0 (lowest) to 63 (highest). </p> |
20 <p>The <i>true</i> priority values range from 0 (lowest) to 63 (highest). </p> |
24 <p>The priority range divides into four broad categories: </p> |
21 <p>The priority range divides into four broad categories: </p> |
25 <table id="GUID-1EAC04DE-B68F-5F95-887C-39E9926F2500"> |
22 <table id="GUID-1EAC04DE-B68F-5F95-887C-39E9926F2500"> |
26 <tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/> |
23 <tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/> |
27 <tbody> |
24 <tbody> |
28 <row> |
25 <row> |
29 <entry><p>0</p> </entry> |
26 <entry><p>0</p> </entry> |
30 <entry><p>This is reserved for the <i>null thread</i>, which puts the processor |
27 <entry><p>This is reserved for the <i>null thread</i>, which puts |
31 into idle mode to save power when no other threads are ready to run. </p> </entry> |
28 the processor into idle mode to save power when no other threads are |
|
29 ready to run. </p> </entry> |
32 </row> |
30 </row> |
33 <row> |
31 <row> |
34 <entry><p>1 - 23 </p> </entry> |
32 <entry><p>1 - 23 </p> </entry> |
35 <entry><p>Used by kernel side threads and user-side applications and servers </p> </entry> |
33 <entry><p>Used by kernel side threads and user-side applications and |
|
34 servers </p> </entry> |
36 </row> |
35 </row> |
37 <row> |
36 <row> |
38 <entry><p>24 -31 </p> </entry> |
37 <entry><p>24 -31 </p> </entry> |
39 <entry><p>Used by kernel side threads and protected system servers, i.e. servers |
38 <entry><p>Used by kernel side threads and protected system servers, |
40 with the <codeph>ProtServ</codeph> capability. </p> </entry> |
39 i.e. servers with the <codeph>ProtServ</codeph> capability. </p> </entry> |
41 </row> |
40 </row> |
42 <row> |
41 <row> |
43 <entry><p>32 - 63 </p> </entry> |
42 <entry><p>32 - 63 </p> </entry> |
44 <entry><p>Reserved for real-time threads running on the kernel side. </p> </entry> |
43 <entry><p>Reserved for real-time threads running on the kernel side. </p> </entry> |
45 </row> |
44 </row> |
46 </tbody> |
45 </tbody> |
47 </tgroup> |
46 </tgroup> |
48 </table> |
47 </table> |
49 <fig id="GUID-5FFD4994-B20D-5095-8F6E-FB1151A4FF79"> |
48 <fig id="GUID-5FFD4994-B20D-5095-8F6E-FB1151A4FF79"> |
50 <image href="GUID-A95FEDD4-106A-5E14-8B64-3E2882C76666_d0e246388_href.png" placement="inline"/> |
49 <image href="GUID-A95FEDD4-106A-5E14-8B64-3E2882C76666_d0e251347_href.png" placement="inline"/> |
51 </fig> |
50 </fig> |
52 <ul> |
51 <ul> |
53 <li id="GUID-2BCF03FE-C23E-5CCA-87CF-4AE9A91FD0D8"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-0194B574-806B-5BA3-B65C-6DC5A80CAB86">Priority scheme for general user-side threads</xref> </p> </li> |
52 <li id="GUID-2BCF03FE-C23E-5CCA-87CF-4AE9A91FD0D8"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-0194B574-806B-5BA3-B65C-6DC5A80CAB86">Priority scheme for general user-side threads</xref> </p> </li> |
54 <li id="GUID-000499D5-EE19-5838-90CD-8C13AC468A52"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-23801A52-4E62-56F4-8D81-E0A417517FDA">Priority scheme for real-time user-side threads</xref> </p> </li> |
53 <li id="GUID-000499D5-EE19-5838-90CD-8C13AC468A52"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-23801A52-4E62-56F4-8D81-E0A417517FDA">Priority scheme for real-time user-side threads</xref> </p> </li> |
55 <li id="GUID-1BA97FE4-F817-50E4-A6DA-6B0B64819811"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">Thread priority value mapping table</xref> </p> </li> |
54 <li id="GUID-1BA97FE4-F817-50E4-A6DA-6B0B64819811"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">Thread priority value mapping table</xref> </p> </li> |
56 <li id="GUID-2BB44CDE-B566-52C0-869C-C60FB8D6AD94"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-E9AFB6A3-ED3E-5110-82C8-E5E15E0AF899">Platform security notes</xref> </p> </li> |
55 <li id="GUID-2BB44CDE-B566-52C0-869C-C60FB8D6AD94"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-E9AFB6A3-ED3E-5110-82C8-E5E15E0AF899">Platform security notes</xref> </p> </li> |
57 </ul> |
56 </ul> |
58 <section id="GUID-0194B574-806B-5BA3-B65C-6DC5A80CAB86"><title>Priority scheme |
57 <section id="GUID-0194B574-806B-5BA3-B65C-6DC5A80CAB86"><title>Priority |
59 for general user-side threads</title> <p>User-side threads do not allocate <i>true</i> priority |
58 scheme for general user-side threads</title> <p>User-side threads |
60 values directly. Instead, they allocate priorities using symbolic values defined |
59 do not allocate <i>true</i> priority values directly. Instead, they |
61 by enums. Symbian platform maps these values to the <i>true</i> value. </p> <p>There |
60 allocate priorities using symbolic values defined by enums. Symbian |
|
61 platform maps these values to the <i>true</i> value. </p> <p>There |
62 are two priority allocation schemes: </p> <ul> |
62 are two priority allocation schemes: </p> <ul> |
63 <li id="GUID-6BE65AEC-DC54-5350-8704-538B5E425352"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-B9022468-F4E7-536B-B1D4-58DAA9EA5914">Process-relative scheme</xref> </p> </li> |
63 <li id="GUID-6BE65AEC-DC54-5350-8704-538B5E425352"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-B9022468-F4E7-536B-B1D4-58DAA9EA5914">Process-relative scheme</xref> </p> </li> |
64 <li id="GUID-BBB502EA-950C-5F8C-8CA2-F5F339000A10"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-7A38EE63-E955-5432-84E1-F35CB45C931E">Process-independent scheme for general user threads</xref> </p> </li> |
64 <li id="GUID-BBB502EA-950C-5F8C-8CA2-F5F339000A10"><p> <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-7A38EE63-E955-5432-84E1-F35CB45C931E">Process-independent scheme for general user threads</xref> </p> </li> |
65 </ul> <p id="GUID-B9022468-F4E7-536B-B1D4-58DAA9EA5914"><b>Process-relative scheme</b> </p> <p>This |
65 </ul> <p id="GUID-B9022468-F4E7-536B-B1D4-58DAA9EA5914"><b>Process-relative |
66 scheme bases the <i>true</i> priority of a thread on the priority of its owning |
66 scheme</b> </p> <p>This scheme bases the <i>true</i> priority of a |
67 process and the priority of the thread relative to the process. This means |
67 thread on the priority of its owning process and the priority of the |
68 that changing the process priority results in a change to the <i>true</i> priority |
68 thread relative to the process. This means that changing the process |
69 of the thread. </p> <p>A process can be assigned one of eight discrete priorities |
69 priority results in a change to the <i>true</i> priority of the thread. </p> <p>A process can be assigned one of eight discrete priorities represented |
70 represented by the individual enumerators of <xref href="GUID-5D289F30-2C88-396D-9748-798055F0AF56.dita"><apiname>TProcessPriority</apiname></xref>, |
70 by the individual enumerators of <xref href="GUID-5D289F30-2C88-396D-9748-798055F0AF56.dita"><apiname>TProcessPriority</apiname></xref>, and range from <xref href="GUID-9B7922A7-6098-3BBD-9ADE-BC21AD6381C3.dita"><apiname>EPriorityLow</apiname></xref>, the lowest, to <xref href="GUID-A35268D0-7EFC-3D58-8C79-E4E619F762F5.dita"><apiname>EPrioritySupervisor</apiname></xref>, the highest. </p> <p>In practice, <i>user processes</i> can only be assigned priorities that are one of |
71 and range from <xref href="GUID-9B7922A7-6098-3BBD-9ADE-BC21AD6381C3.dita"><apiname>EPriorityLow</apiname></xref>, the lowest, to <xref href="GUID-A35268D0-7EFC-3D58-8C79-E4E619F762F5.dita"><apiname>EPrioritySupervisor</apiname></xref>, |
71 the values: </p> <ul> |
72 the highest. </p> <p>In practice, <i>user processes</i> can only be assigned |
|
73 priorities that are one of the values: </p> <ul> |
|
74 <li id="GUID-85AA4A1D-A168-5AEF-9D4C-DC14C28686B2"><p> <xref href="GUID-9B7922A7-6098-3BBD-9ADE-BC21AD6381C3.dita"><apiname>EPriorityLow</apiname></xref> <codeph/> </p> </li> |
72 <li id="GUID-85AA4A1D-A168-5AEF-9D4C-DC14C28686B2"><p> <xref href="GUID-9B7922A7-6098-3BBD-9ADE-BC21AD6381C3.dita"><apiname>EPriorityLow</apiname></xref> <codeph/> </p> </li> |
75 <li id="GUID-45B720BB-3696-545F-B966-A2EA4B37AE5D"><p> <xref href="GUID-8778A277-DA7F-34A0-8472-29226DEC2CCE.dita"><apiname>EPriorityBackground</apiname></xref> </p> </li> |
73 <li id="GUID-45B720BB-3696-545F-B966-A2EA4B37AE5D"><p> <xref href="GUID-8778A277-DA7F-34A0-8472-29226DEC2CCE.dita"><apiname>EPriorityBackground</apiname></xref> </p> </li> |
76 <li id="GUID-DF2708D4-B670-5B15-B587-CB71EAC99045"><p> <xref href="GUID-A62CF9B2-63E3-31E0-A51E-E04F2E2EB38F.dita"><apiname>EPriorityForeGround</apiname></xref> </p> </li> |
74 <li id="GUID-DF2708D4-B670-5B15-B587-CB71EAC99045"><p> <xref href="GUID-A62CF9B2-63E3-31E0-A51E-E04F2E2EB38F.dita"><apiname>EPriorityForeGround</apiname></xref> </p> </li> |
77 <li id="GUID-9C68DD95-2AB6-57D0-9966-D83144788458"><p> <xref href="GUID-8995D880-69B7-3C31-891B-7A2C57E372FE.dita"><apiname>EPriorityHigh</apiname></xref> </p> </li> |
75 <li id="GUID-9C68DD95-2AB6-57D0-9966-D83144788458"><p> <xref href="GUID-8995D880-69B7-3C31-891B-7A2C57E372FE.dita"><apiname>EPriorityHigh</apiname></xref> </p> </li> |
78 </ul> <p>There are a further four process priorities that a user process is |
76 </ul> <p>There are a further four process priorities that a user process |
79 not permitted to set: <codeph>EPriorityWindowServer</codeph>, <codeph>EPriorityFileServer</codeph>, <codeph>EPriorityRealTimeServer</codeph> and <codeph>EPrioritySupervisor</codeph>. </p> <p>A process priority can be assigned: </p> <ul> |
77 is not permitted to set: <codeph>EPriorityWindowServer</codeph>, <codeph>EPriorityFileServer</codeph>, <codeph>EPriorityRealTimeServer</codeph> and <codeph>EPrioritySupervisor</codeph>. </p> <p>A process priority |
80 <li id="GUID-CC4FA12C-BFDD-5F75-BC18-B742BCACEECF"><p>when the associated <filepath>.exe</filepath> is |
78 can be assigned: </p> <ul> |
81 built; this is done by specifying the value in the <filepath>.mmp</filepath> file |
79 <li id="GUID-CC4FA12C-BFDD-5F75-BC18-B742BCACEECF"><p>when the associated <filepath>.exe</filepath> is built; this is done by specifying the value in |
82 that defines the project. </p> </li> |
80 the <filepath>.mmp</filepath> file that defines the project. </p> </li> |
83 <li id="GUID-B86220D9-B10D-5506-AD90-73E7F8D7A089"><p>by calling <xref href="GUID-9DD1EA2B-DC59-315C-8E9C-CE6D9461B695.dita#GUID-9DD1EA2B-DC59-315C-8E9C-CE6D9461B695/GUID-189A64CB-F2EA-3C8F-A7A7-01CBF8FDE67A"><apiname>RProcess::SetPriority()</apiname></xref> and |
81 <li id="GUID-B86220D9-B10D-5506-AD90-73E7F8D7A089"><p>by calling <xref href="GUID-9DD1EA2B-DC59-315C-8E9C-CE6D9461B695.dita#GUID-9DD1EA2B-DC59-315C-8E9C-CE6D9461B695/GUID-189A64CB-F2EA-3C8F-A7A7-01CBF8FDE67A"><apiname>RProcess::SetPriority()</apiname></xref> and passing one of the <xref href="GUID-5D289F30-2C88-396D-9748-798055F0AF56.dita"><apiname>TProcessPriority</apiname></xref> enum values. </p> </li> |
84 passing one of the <xref href="GUID-5D289F30-2C88-396D-9748-798055F0AF56.dita"><apiname>TProcessPriority</apiname></xref> enum values. </p> </li> |
82 </ul> <p>The priority of a thread <i>relative</i> to |
85 </ul> <p>See also : <xref href="GUID-8DB5E558-9774-5CC3-AF8C-6C50D9FE0496.dita">Using |
83 a process is assigned by calling <xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita#GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5/GUID-8E412361-AE54-3585-AF2A-45D4A53F8B03"><apiname>RThread::SetPriority()</apiname></xref> and passing one of the five <xref href="GUID-8708AFB7-92CC-34FC-9FBB-E6B16472B99D.dita"><apiname>TThreadPriority</apiname></xref> enum |
86 Makmake</xref> in the <xref href="GUID-B21141D4-3BFE-59C9-8D5F-147A93BE1C95.dita">Build |
84 values: </p> <ul> |
87 Tools Guide</xref>. </p> <p>The priority of a thread <i>relative</i> to a |
|
88 process is assigned by calling <xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita#GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5/GUID-8E412361-AE54-3585-AF2A-45D4A53F8B03"><apiname>RThread::SetPriority()</apiname></xref> and |
|
89 passing one of the five <xref href="GUID-8708AFB7-92CC-34FC-9FBB-E6B16472B99D.dita"><apiname>TThreadPriority</apiname></xref> enum values: </p> <ul> |
|
90 <li id="GUID-BCFFB27F-5CEB-58E8-A859-C82273CB7FDC"><p> <xref href="GUID-DF41A24C-6873-37E6-834A-98CDFC8D54FB.dita"><apiname>EPriorityMuchLess</apiname></xref> </p> </li> |
85 <li id="GUID-BCFFB27F-5CEB-58E8-A859-C82273CB7FDC"><p> <xref href="GUID-DF41A24C-6873-37E6-834A-98CDFC8D54FB.dita"><apiname>EPriorityMuchLess</apiname></xref> </p> </li> |
91 <li id="GUID-21C1A24C-483D-579B-BA56-31B3694215CE"><p> <xref href="GUID-0429DE71-44B4-3764-A62B-AD937E6AD355.dita"><apiname> EPriorityLess</apiname></xref> </p> </li> |
86 <li id="GUID-21C1A24C-483D-579B-BA56-31B3694215CE"><p> <xref href="GUID-0429DE71-44B4-3764-A62B-AD937E6AD355.dita"><apiname> EPriorityLess</apiname></xref> </p> </li> |
92 <li id="GUID-48747F5D-8F0E-5C57-8858-35D8881B1DB7"><p> <xref href="GUID-2ACE5CF0-7E8B-35FF-8ABC-6917B2F68BB1.dita"><apiname>EPriorityNormal</apiname></xref> </p> </li> |
87 <li id="GUID-48747F5D-8F0E-5C57-8858-35D8881B1DB7"><p> <xref href="GUID-2ACE5CF0-7E8B-35FF-8ABC-6917B2F68BB1.dita"><apiname>EPriorityNormal</apiname></xref> </p> </li> |
93 <li id="GUID-78DEBC15-DFD8-5384-8358-3744E2C1DDBE"><p> <xref href="GUID-34B6B121-2E45-36FE-B0FA-E8272E2F1D10.dita"><apiname>EPriorityMore</apiname></xref> </p> </li> |
88 <li id="GUID-78DEBC15-DFD8-5384-8358-3744E2C1DDBE"><p> <xref href="GUID-34B6B121-2E45-36FE-B0FA-E8272E2F1D10.dita"><apiname>EPriorityMore</apiname></xref> </p> </li> |
94 <li id="GUID-AE42DA32-09CA-5C8B-B9AF-2A68E66E6218"><p> <xref href="GUID-4F19A64D-FBBE-34F2-8387-1449E49DC923.dita"><apiname> EPriorityMuchMore</apiname></xref> </p> </li> |
89 <li id="GUID-AE42DA32-09CA-5C8B-B9AF-2A68E66E6218"><p> <xref href="GUID-4F19A64D-FBBE-34F2-8387-1449E49DC923.dita"><apiname> EPriorityMuchMore</apiname></xref> </p> </li> |
95 </ul> <p>The <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">thread |
90 </ul> <p>The <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">thread priority value mapping table</xref> shows the <i>true</i> priority |
96 priority value mapping table</xref> shows the <i>true</i> priority of a thread |
91 of a thread based on the combination of process priority and process-relative |
97 based on the combination of process priority and process-relative thread priority </p> <p id="GUID-7A38EE63-E955-5432-84E1-F35CB45C931E"><b>Process-independent scheme |
92 thread priority </p> <p id="GUID-7A38EE63-E955-5432-84E1-F35CB45C931E"><b>Process-independent |
98 for general user threads</b> </p> <p>In this scheme, the <i>true</i> priority |
93 scheme for general user threads</b> </p> <p>In this scheme, the <i>true</i> priority of a thread is independent of the priority of its |
99 of a thread is independent of the priority of its owning process. Changing |
94 owning process. Changing the priority of the underlying process has |
100 the priority of the underlying process has no effect on the <i>true</i> priority |
95 no effect on the <i>true</i> priority of the thread. </p> <p>The priority |
101 of the thread. </p> <p>The priority of a thread is assigned by calling <xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita#GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5/GUID-8E412361-AE54-3585-AF2A-45D4A53F8B03"><apiname>RThread::SetPriority()</apiname></xref> and |
96 of a thread is assigned by calling <xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita#GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5/GUID-8E412361-AE54-3585-AF2A-45D4A53F8B03"><apiname>RThread::SetPriority()</apiname></xref> and passing one of the <xref href="GUID-8708AFB7-92CC-34FC-9FBB-E6B16472B99D.dita"><apiname>TThreadPriority</apiname></xref> enum values |
102 passing one of the <xref href="GUID-8708AFB7-92CC-34FC-9FBB-E6B16472B99D.dita"><apiname>TThreadPriority</apiname></xref> enum values listed below. |
97 listed below. Note that the set of enum values splits into two logical |
103 Note that the set of enum values splits into two logical groupings based on |
98 groupings based on their equivalence to process-relative values. See |
104 their equivalence to process-relative values. See the <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">thread priority value mapping table</xref>. </p> <table id="GUID-A0397BB8-AAC7-5F79-B94F-68103B66132C"> |
99 the <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">thread priority value mapping table</xref>. </p> <table id="GUID-A0397BB8-AAC7-5F79-B94F-68103B66132C"> |
105 <tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/> |
100 <tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/> |
106 <tbody> |
101 <tbody> |
107 <row> |
102 <row> |
108 <entry><p> <b> Group 1 </b> </p> </entry> |
103 <entry><p> <b> Group 1 </b> </p> </entry> |
109 <entry><p> <b> Group 2 </b> </p> </entry> |
104 <entry><p> <b> Group 2 </b> </p> </entry> |
123 <li id="GUID-E41572FD-0C50-54BC-98C6-857A8D86CCD7"><p> <xref href="GUID-E49C7DFA-4604-310C-915C-F278382A796A.dita"><apiname>EPriorityAbsoluteHighNormal</apiname></xref> </p> </li> |
118 <li id="GUID-E41572FD-0C50-54BC-98C6-857A8D86CCD7"><p> <xref href="GUID-E49C7DFA-4604-310C-915C-F278382A796A.dita"><apiname>EPriorityAbsoluteHighNormal</apiname></xref> </p> </li> |
124 </ul> </entry> |
119 </ul> </entry> |
125 </row> |
120 </row> |
126 </tbody> |
121 </tbody> |
127 </tgroup> |
122 </tgroup> |
128 </table> <p>The <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">thread |
123 </table> <p>The <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">thread priority value mapping table</xref> shows the resulting <i>true</i> priority of the thread. </p> </section> |
129 priority value mapping table</xref> shows the resulting <i>true</i> priority |
124 <section id="GUID-23801A52-4E62-56F4-8D81-E0A417517FDA"><title>Priority |
130 of the thread. </p> </section> |
125 scheme for real-time user-side threads</title> <p>This scheme is the |
131 <section id="GUID-23801A52-4E62-56F4-8D81-E0A417517FDA"><title>Priority scheme |
126 same as the <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-7A38EE63-E955-5432-84E1-F35CB45C931E">process-independent scheme for general user threads</xref>, but with |
132 for real-time user-side threads</title> <p>This scheme is the same as the <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-7A38EE63-E955-5432-84E1-F35CB45C931E">process-independent |
127 one essential difference - the range of <xref href="GUID-8708AFB7-92CC-34FC-9FBB-E6B16472B99D.dita"><apiname>TThreadPriority</apiname></xref> enum values to be passed to <xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita#GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5/GUID-8E412361-AE54-3585-AF2A-45D4A53F8B03"><apiname>RThread::SetPriority()</apiname></xref> is as shown below. These priorities map to the <i>true</i> priority |
133 scheme for general user threads</xref>, but with one essential difference |
128 values in the range 24 -31, and can only be set by executables having |
134 - the range of <xref href="GUID-8708AFB7-92CC-34FC-9FBB-E6B16472B99D.dita"><apiname>TThreadPriority</apiname></xref> enum values to be passed |
129 the <codeph>ProtServ</codeph> capability. This range is referred to |
135 to <xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita#GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5/GUID-8E412361-AE54-3585-AF2A-45D4A53F8B03"><apiname>RThread::SetPriority()</apiname></xref> is as shown below. These priorities |
130 as the real time range. </p> <ul> |
136 map to the <i>true</i> priority values in the range 24 -31, and can only be |
|
137 set by executables having the <codeph>ProtServ</codeph> capability. This range |
|
138 is referred to as the real time range. </p> <ul> |
|
139 <li id="GUID-78ACFC22-4FB7-5E90-B6E2-9EF39EA9A3F5"><p> <xref href="GUID-7574A754-ED28-3FE1-85BB-93F110DE8E50.dita"><apiname>EPriorityAbsoluteRealTime1</apiname></xref> </p> </li> |
131 <li id="GUID-78ACFC22-4FB7-5E90-B6E2-9EF39EA9A3F5"><p> <xref href="GUID-7574A754-ED28-3FE1-85BB-93F110DE8E50.dita"><apiname>EPriorityAbsoluteRealTime1</apiname></xref> </p> </li> |
140 <li id="GUID-3ADBFE8D-E7D9-5316-B06E-E3C514F4221E"><p> <xref href="GUID-2561145A-9506-31F5-A0EA-24609EC71412.dita"><apiname>EPriorityAbsoluteRealTime2</apiname></xref> </p> </li> |
132 <li id="GUID-3ADBFE8D-E7D9-5316-B06E-E3C514F4221E"><p> <xref href="GUID-2561145A-9506-31F5-A0EA-24609EC71412.dita"><apiname>EPriorityAbsoluteRealTime2</apiname></xref> </p> </li> |
141 <li id="GUID-90F0E400-AB37-52CC-B01E-2D7C3E589111"><p> <xref href="GUID-39A7F794-B7B1-3C0C-AFFF-956C71CE529F.dita"><apiname>EPriorityAbsoluteRealTime3</apiname></xref> </p> </li> |
133 <li id="GUID-90F0E400-AB37-52CC-B01E-2D7C3E589111"><p> <xref href="GUID-39A7F794-B7B1-3C0C-AFFF-956C71CE529F.dita"><apiname>EPriorityAbsoluteRealTime3</apiname></xref> </p> </li> |
142 <li id="GUID-DDB4B69C-9BBD-5E4B-B87C-CF52B4BDAA85"><p> <xref href="GUID-DCDD7812-10F8-35A1-9DAD-EFDAC6EA874B.dita"><apiname> EPriorityAbsoluteRealTime4</apiname></xref> </p> </li> |
134 <li id="GUID-DDB4B69C-9BBD-5E4B-B87C-CF52B4BDAA85"><p> <xref href="GUID-DCDD7812-10F8-35A1-9DAD-EFDAC6EA874B.dita"><apiname> EPriorityAbsoluteRealTime4</apiname></xref> </p> </li> |
143 <li id="GUID-91DEE716-6F45-51C2-8139-B9CB1AE5065B"><p> <xref href="GUID-F3872848-57CA-3682-80E2-39E87B7B3656.dita"><apiname>EPriorityAbsoluteRealTime5</apiname></xref> </p> </li> |
135 <li id="GUID-91DEE716-6F45-51C2-8139-B9CB1AE5065B"><p> <xref href="GUID-F3872848-57CA-3682-80E2-39E87B7B3656.dita"><apiname>EPriorityAbsoluteRealTime5</apiname></xref> </p> </li> |
144 <li id="GUID-01B2B0B9-4242-5D8E-83B2-2658CF68548F"><p> <xref href="GUID-D3FE9747-0CD8-3E0A-829E-3D7184AE8431.dita"><apiname>EPriorityAbsoluteRealTime6</apiname></xref> </p> </li> |
136 <li id="GUID-01B2B0B9-4242-5D8E-83B2-2658CF68548F"><p> <xref href="GUID-D3FE9747-0CD8-3E0A-829E-3D7184AE8431.dita"><apiname>EPriorityAbsoluteRealTime6</apiname></xref> </p> </li> |
145 <li id="GUID-6581842F-C83C-53A5-A567-F1D4BE97488C"><p> <xref href="GUID-A6BF84AA-2421-3DB0-A30D-B9D3B7E70B21.dita"><apiname>EPriorityAbsoluteRealTime7</apiname></xref> </p> </li> |
137 <li id="GUID-6581842F-C83C-53A5-A567-F1D4BE97488C"><p> <xref href="GUID-A6BF84AA-2421-3DB0-A30D-B9D3B7E70B21.dita"><apiname>EPriorityAbsoluteRealTime7</apiname></xref> </p> </li> |
146 <li id="GUID-C7AB328B-B910-51D2-ADB0-5E8A33AFCD69"><p> <xref href="GUID-84C4AED5-8AA8-31F0-9E77-6BBACE192763.dita"><apiname>EPriorityAbsoluteRealTime8</apiname></xref> </p> </li> |
138 <li id="GUID-C7AB328B-B910-51D2-ADB0-5E8A33AFCD69"><p> <xref href="GUID-84C4AED5-8AA8-31F0-9E77-6BBACE192763.dita"><apiname>EPriorityAbsoluteRealTime8</apiname></xref> </p> </li> |
147 </ul> <p>The <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">thread |
139 </ul> <p>The <xref href="GUID-7B173E02-9697-51F4-A7E8-795AEF547109.dita#GUID-7B173E02-9697-51F4-A7E8-795AEF547109/GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF">thread priority value mapping table</xref> shows the resulting <i>true</i> priority of the thread. </p> </section> |
148 priority value mapping table</xref> shows the resulting <i>true</i> priority |
140 <section id="GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF"><title>Thread |
149 of the thread. </p> </section> |
141 priority value mapping table</title> <p>This table shows the effect |
150 <section id="GUID-F5B98A28-EEDA-58BD-A6CC-62C1621D44DF"><title>Thread priority |
142 of setting priorities, and the resulting <i>true</i> priority values. |
151 value mapping table</title> <p>This table shows the effect of setting priorities, |
143 You need to be aware that this may change in the future, and you should |
152 and the resulting <i>true</i> priority values. You need to be aware that this |
144 never synchronise threads on the basis of thread priorities. If you |
153 may change in the future, and you should never synchronise threads on the |
145 need to synchronise threads, use mutexes or semaphores. </p> <p>Notes </p> <ul> |
154 basis of thread priorities. If you need to synchronise threads, use mutexes |
146 <li id="GUID-CBC69A23-E3EF-56BC-A915-2770EBFB76C4"><p>True priority |
155 or semaphores. </p> <p>Notes </p> <ul> |
147 values in the shaded region can only be accessed by threads running |
156 <li id="GUID-CBC69A23-E3EF-56BC-A915-2770EBFB76C4"><p>True priority values |
148 in processes with the <codeph>ProtServ</codeph> capability. </p> </li> |
157 in the shaded region can only be accessed by threads running in processes |
|
158 with the <codeph>ProtServ</codeph> capability. </p> </li> |
|
159 <li id="GUID-1F8FC263-3C39-5E3C-A186-6D5D4DF7D6D3"><p>The process-priority |
149 <li id="GUID-1F8FC263-3C39-5E3C-A186-6D5D4DF7D6D3"><p>The process-priority |
160 values : <xref href="GUID-972ADC0C-546E-3D24-9071-02B074DC1540.dita"><apiname>EPriorityWindowServer</apiname></xref>, <xref href="GUID-A19C5464-A1DA-3EEC-B81B-41690EBB3DB2.dita"><apiname>EPriorityFileServer</apiname></xref> and <xref href="GUID-A35268D0-7EFC-3D58-8C79-E4E619F762F5.dita"><apiname>EPrioritySupervisor</apiname></xref> all |
150 values : <xref href="GUID-972ADC0C-546E-3D24-9071-02B074DC1540.dita"><apiname>EPriorityWindowServer</apiname></xref>, <xref href="GUID-A19C5464-A1DA-3EEC-B81B-41690EBB3DB2.dita"><apiname>EPriorityFileServer</apiname></xref> and <xref href="GUID-A35268D0-7EFC-3D58-8C79-E4E619F762F5.dita"><apiname>EPrioritySupervisor</apiname></xref> all map to the same range |
161 map to the same range of priorities. Along with <xref href="GUID-AAA610A8-48D8-3642-94E8-6C9747170DA9.dita"><apiname>EPriorityRealTimeServer</apiname></xref>, |
151 of priorities. Along with <xref href="GUID-AAA610A8-48D8-3642-94E8-6C9747170DA9.dita"><apiname>EPriorityRealTimeServer</apiname></xref>, these have historically been used for system servers and other |
162 these have historically been used for system servers and other processes needing |
152 processes needing access to high priorities suitable for real-time |
163 access to high priorities suitable for real-time tasks, and their use requires <codeph>ProtServ</codeph> capability. </p> </li> |
153 tasks, and their use requires <codeph>ProtServ</codeph> capability. </p> </li> |
164 <li id="GUID-3256F08A-AD30-5378-BFA9-140688B1CDB6"><p>Note that <codeph>ProtServ</codeph> capability |
154 <li id="GUID-3256F08A-AD30-5378-BFA9-140688B1CDB6"><p>Note that <codeph>ProtServ</codeph> capability will not be granted to general applications |
165 will not be granted to general applications for the purpose of gaining access |
155 for the purpose of gaining access to the very high thread priorities. |
166 to the very high thread priorities. This risks breaking important system functionality. </p> </li> |
156 This risks breaking important system functionality. </p> </li> |
167 </ul> <fig id="GUID-6BF93712-F8AA-5D08-A5D4-FEB6B22592D8"> |
157 </ul> <fig id="GUID-6BF93712-F8AA-5D08-A5D4-FEB6B22592D8"> |
168 <image href="GUID-B9306D01-1DE5-511A-AC1A-6E3E9749BA89_d0e246991_href.png" placement="inline"/> |
158 <image href="GUID-B9306D01-1DE5-511A-AC1A-6E3E9749BA89_d0e251942_href.png" placement="inline"/> |
169 </fig> <p>Note that we have used <i>E'</i> as an abbreviation for <i>EPriority</i> in |
159 </fig> <p>Note that we have used <i>E'</i> as an abbreviation for <i>EPriority</i> in this diagram. </p> </section> |
170 this diagram. </p> </section> |
160 <section id="GUID-E9AFB6A3-ED3E-5110-82C8-E5E15E0AF899"><title>Platform |
171 <section id="GUID-E9AFB6A3-ED3E-5110-82C8-E5E15E0AF899"><title>Platform security |
161 security notes</title> <p>Platform security restrictions prevent thread |
172 notes</title> <p>Platform security restrictions prevent thread and process |
162 and process priorities from being modified by another user process. |
173 priorities from being modified by another user process. There is one exception: |
163 There is one exception: by default, applications have “Priority Control” |
174 by default, applications have “Priority Control” enabled for them which allows |
164 enabled for them which allows the window server to switch them between |
175 the window server to switch them between foreground and background process |
165 foreground and background process priorities depending on which has |
176 priorities depending on which has foreground focus. </p> </section> |
166 foreground focus. </p> </section> |
177 </conbody></concept> |
167 </conbody></concept> |