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implement a interface that change query process priority (nice value in linux), and add a column to PROCESSLIST
–
maybe we could implement a new token inside queries?
SELECT /* NICE_VALUE=-20 */ * FROM table WHERE ....
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UPDATE /* NICE_VALUE=-20 */ table SET xxxx .....
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and a process control interface
RENICE <query id> <new nice value>
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–
after query done (end of query), the server should go back to a normal priority (windows) or a nice value (linux)
set a global variable @@system_thread_default_priority (default = 0) to set default process priority
in windows we have this priorities:
IDLE_PRIORITY_CLASS
BELOW_NORMAL_PRIORITY_CLASS
NORMAL_PRIORITY_CLASS
ABOVE_NORMAL_PRIORITY_CLASS
HIGH_PRIORITY_CLASS
REALTIME_PRIORITY_CLASS
http://msdn.microsoft.com/en-us/library/windows/desktop/ms685100(v=vs.85).aspx
in linux we have a value from -20 (high priority) to 20 (low priority), it's the nice value, we can renice via console or execute mysql with nice -n 999 mysqld .... command
i think that mysqld should not use realtime priority but i don't know if we can use it, it's something that automation control systems use, control a GPIO for example, not a general process schedule feature
the point is... when using windows we have a priority value, when using linux (posix) we have another priority value, maybe we should have a linux nice value/windows class priority interface ? maybe:
| linux |
windows |
| from -20 to -11 |
HIGH_PRIORITY_CLASS |
| from -10 to -1 |
ABOVE_NORMAL_PRIORITY_CLASS |
| 0 |
NORMAL_PRIORITY_CLASS |
| from 1 to 10 |
BELOW_NORMAL_PRIORITY_CLASS |
| from 11 to 20 |
IDLE_PRIORITY_CLASS |
maybe use the microsoft 'nice values' (base priority) starting from 1 to 31
or use the cygwin version of nice_to_winprio and winprio_to_nice:
http://cygwin.com/cgi-bin/cvsweb.cgi/src/winsup/cygwin/miscfuncs.cc?rev=1.98&content-type=text/x-cvsweb-markup&cvsroot=src
/* Get a default value for the nice factor. When changing these values,
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have a look into the below function nice_to_winprio. The values must
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match the layout of the static "priority" array. */
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int
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winprio_to_nice (DWORD prio)
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{
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switch (prio)
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{
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case REALTIME_PRIORITY_CLASS:
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return -20;
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case HIGH_PRIORITY_CLASS:
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return -16;
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case ABOVE_NORMAL_PRIORITY_CLASS:
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return -8;
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case NORMAL_PRIORITY_CLASS:
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return 0;
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case BELOW_NORMAL_PRIORITY_CLASS:
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return 8;
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case IDLE_PRIORITY_CLASS:
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return 16;
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}
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return 0;
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}
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/* Get a Win32 priority matching the incoming nice factor. The incoming
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nice is limited to the interval [-NZERO,NZERO-1]. */
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DWORD
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nice_to_winprio (int &nice)
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{
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static const DWORD priority[] =
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{
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REALTIME_PRIORITY_CLASS, /* 0 */
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HIGH_PRIORITY_CLASS, /* 1 */
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HIGH_PRIORITY_CLASS,
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HIGH_PRIORITY_CLASS,
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HIGH_PRIORITY_CLASS,
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HIGH_PRIORITY_CLASS,
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HIGH_PRIORITY_CLASS,
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HIGH_PRIORITY_CLASS, /* 7 */
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ABOVE_NORMAL_PRIORITY_CLASS, /* 8 */
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ABOVE_NORMAL_PRIORITY_CLASS,
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ABOVE_NORMAL_PRIORITY_CLASS,
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ABOVE_NORMAL_PRIORITY_CLASS,
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ABOVE_NORMAL_PRIORITY_CLASS,
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ABOVE_NORMAL_PRIORITY_CLASS,
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ABOVE_NORMAL_PRIORITY_CLASS,
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ABOVE_NORMAL_PRIORITY_CLASS, /* 15 */
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NORMAL_PRIORITY_CLASS, /* 16 */
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NORMAL_PRIORITY_CLASS,
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NORMAL_PRIORITY_CLASS,
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NORMAL_PRIORITY_CLASS,
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NORMAL_PRIORITY_CLASS,
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NORMAL_PRIORITY_CLASS,
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NORMAL_PRIORITY_CLASS,
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NORMAL_PRIORITY_CLASS, /* 23 */
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BELOW_NORMAL_PRIORITY_CLASS, /* 24 */
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BELOW_NORMAL_PRIORITY_CLASS,
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BELOW_NORMAL_PRIORITY_CLASS,
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BELOW_NORMAL_PRIORITY_CLASS,
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BELOW_NORMAL_PRIORITY_CLASS,
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BELOW_NORMAL_PRIORITY_CLASS,
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BELOW_NORMAL_PRIORITY_CLASS,
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BELOW_NORMAL_PRIORITY_CLASS, /* 31 */
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IDLE_PRIORITY_CLASS, /* 32 */
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IDLE_PRIORITY_CLASS,
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IDLE_PRIORITY_CLASS,
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IDLE_PRIORITY_CLASS,
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IDLE_PRIORITY_CLASS,
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IDLE_PRIORITY_CLASS,
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IDLE_PRIORITY_CLASS,
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IDLE_PRIORITY_CLASS /* 39 */
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};
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if (nice < -NZERO)
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nice = -NZERO;
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else if (nice > NZERO - 1)
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nice = NZERO - 1;
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DWORD prio = priority[nice + NZERO];
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return prio;
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}
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