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Scheduler: fundamentals of capacity classification

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Workers asking for the next task are classified as belonging
to some fraction of the free capacity, based on the distance
to the closest next Activity known to the scheduler
This commit is contained in:
Fischlurch 2023-10-23 04:07:38 +02:00
parent b61ca94ee5
commit 84ca2460c1
4 changed files with 236 additions and 15 deletions
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70
src/vault/gear/load-controller.hpp
View file

@ -31,6 +31,39 @@
** are designed to withstand a short-term imbalance, expecting that general
** engine parametrisation will be adjusted based on moving averages.
**
** # Principles for Engine Load Control
**
** Scheduling and dispatch of Activities are driven by active workers invoking
** the Scheduler-Service to retrieve the next piece of work. While this scheme
** ensures that the scarce resource (computation or IO capacity) is directed
** towards the most urgent next task, achieving a smooth operation of the engine
** without wasted capacity requires additionally to control the request cycles
** of the workers, possibly removing excess capacity. Whenever a worker pulls
** the next task, an assessment of the timing situation is conducted, and the
** worker is placed into some partition of the overall available capacity,
** to reflect the current load and demand. Workers are thus moved between
** the segments, preferring to assign work to workers already in the active
** segment, thereby allowing idle workers to be shut down after some time.
**
** The key element to decide upon the classification of a worker is the current
** scheduling situation: are some Activities overdue? does the next Activity
** to be considered reach far into the future? If there is immediately imminent
** work, then capacity is kept around; otherwise the capacity can be considered
** to be in excess for now. A worker not required right now can be sent into a
** targeted sleep delay, in order to shift its capacity into a zone where it
** will more likely be required. It is essential to apply some randomisation
** on such capacity shifts, in order to achieve an even distribution of free
** capacity and avoid contention between workers asking for new assignments.
**
** When a worker becomes available and is not needed at the moment, the first
** thing to check is the time of the next approaching Activity; this worker
** can then be directed close to this next task, which thereby has been tended
** for and can be marked accordingly. Any further worker appearing meanwhile
** can then be directed into the time zone _after_ the next approaching task.
** Workers immediately returning from active work are always preferred for
** assigning new tasks, while workers returning from idle state are typically
** sent back into idle state, unless there is direct need for more capacity.
**
** @see scheduler.hpp
** @see SchedulerStress_test
**
@ -59,7 +92,27 @@ namespace gear {
// using util::isnil;
// using std::string;
using std::chrono::microseconds;
using lib::time::Time;
using lib::time::FSecs;
using lib::time::Offset;
using lib::time::Duration;
using std::chrono_literals::operator ""ms;
using std::chrono_literals::operator ""us;
namespace { // Scheduler default config
inline TimeValue
_uTicks (std::chrono::microseconds us)
{
return TimeValue{us.count()};
}
Duration SLEEP_HORIZON{_uTicks (20ms)};
Duration WORK_HORIZON {_uTicks ( 5ms)};
Duration NOW_HORIZON {_uTicks (50us)};
}
/**
@ -104,15 +157,20 @@ namespace gear {
,IDLETIME ///< time to go to sleep
};
Capacity
classifyCapacity() const
/** classification of time horizon for scheduling */
static Capacity
classifyCapacity (Offset off)
{
UNIMPLEMENTED ("establish a categorisation for available capacity");
if (off > SLEEP_HORIZON) return IDLETIME;
if (off > WORK_HORIZON) return WORKTIME;
if (off > NOW_HORIZON) return NEARTIME;
if (off > Time::ZERO) return SPINTIME;
else return DISPATCH;
}
microseconds
scatteredDelayTime()
Time
scatteredDelayTime (Capacity capacity)
{
UNIMPLEMENTED ("establish a randomised targeted delay time");
}

4
src/vault/gear/scheduler.hpp
View file

@ -64,6 +64,10 @@ namespace gear {
// using util::isnil;
// using std::string;
using std::move;
using lib::time::Time;
using lib::time::FSecs;
using lib::time::Offset;
using lib::time::Duration;
namespace { // Scheduler default config

45
tests/vault/gear/scheduler-load-control-test.cpp
View file

@ -45,6 +45,7 @@ namespace test {
// using lib::time::FrameRate;
// using lib::time::Offset;
// using lib::time::Time;
using Capacity = LoadController::Capacity;
@ -63,19 +64,59 @@ namespace test {
run (Arg)
{
simpleUsage();
classifyTimings();
walkingDeadline();
setupLalup();
}
/** @test TODO demonstrate a simple usage scenario
* @todo WIP 10/23 ✔ define ⟶ 🔁 implement
* @todo WIP 10/23 🔁 define ⟶ 🔁 implement
*/
void
simpleUsage()
{
BlockFlowAlloc bFlow;
LoadController lcontrl{bFlow};
LoadController ctrl{bFlow};
}
/** @test verify classification of time horizon for scheduling.
* - if the next planned Activity lies beyond the SLEEP_HORIZON,
* then the current thread can be considered part of the _idle capacity_
* - in a similar way, WORK_HORIZON delineates the zone of repeated incoming
* Activities from the zone considered part of current active operation
* - Activities within the NOW_HORIZON can be awaited by yield-spinning
* - and any event from current into the past will be scheduled right away
* @todo WIP 10/23 ✔ define ⟶ ✔ implement
*/
void
classifyTimings()
{
BlockFlowAlloc bFlow;
LoadController ctrl{bFlow};
Time next{0,10};
Time ut{1,0};
Time t1{0,9};
Time t2{next - SLEEP_HORIZON};
Time t21{t2 + ut};
Time t3{next - WORK_HORIZON};
Time t31{t3 + ut};
Time t4{next - NOW_HORIZON};
CHECK (Capacity::IDLETIME == LoadController::classifyCapacity (Offset{next - ut }));
CHECK (Capacity::IDLETIME == LoadController::classifyCapacity (Offset{next - t1 }));
CHECK (Capacity::WORKTIME == LoadController::classifyCapacity (Offset{next - t2 }));
CHECK (Capacity::WORKTIME == LoadController::classifyCapacity (Offset{next - t21}));
CHECK (Capacity::NEARTIME == LoadController::classifyCapacity (Offset{next - t3 }));
CHECK (Capacity::NEARTIME == LoadController::classifyCapacity (Offset{next - t31}));
CHECK (Capacity::SPINTIME == LoadController::classifyCapacity (Offset{next - t4 }));
CHECK (Capacity::DISPATCH == LoadController::classifyCapacity (Offset::ZERO ));
CHECK (Capacity::DISPATCH == LoadController::classifyCapacity (Offset{t4 - next }));
}

132
wiki/thinkPad.ichthyo.mm
View file

@ -81970,6 +81970,9 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
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@ -81991,6 +81994,11 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
<node BACKGROUND_COLOR="#d2beaf" COLOR="#5c4d6e" CREATED="1697810722994" HGAP="47" ID="ID_720864528" MODIFIED="1697810766219" TEXT="sp&#xe4;ter wird hier eine globale Engine-Parametrisierung einflie&#xdf;en" VSHIFT="-6">
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@ -82436,6 +82444,30 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
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<node CREATED="1698020524734" ID="ID_1985773186" MODIFIED="1698020550679" TEXT="hier hilft eine probabilistische Betrachtung &#x27f6; Flow">
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<node CREATED="1698020696047" ID="ID_540079176" MODIFIED="1698020717690" TEXT="man extrahiert einen gewissen Anteil der Sleep-Phase"/>
<node CREATED="1698020770133" ID="ID_1232823328" MODIFIED="1698020783240" TEXT="und verteilt sie um auf die aktiv-Phase hinter dem n&#xe4;chsten Termin"/>
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<head/>
<body>
<p>
....denn dann kommen die periodischen Worker sofort zum Zug
</p>
</body>
</html></richcontent>
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</node>
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<font NAME="SansSerif" SIZE="14"/>
<icon BUILTIN="yes"/>
@ -82483,13 +82515,95 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
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</node>
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<head>
</head>
<body>
<p>
sent to work
</p>
</body>
</html>
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<head>
</head>
<body>
<p>
reserved for next task
</p>
</body>
</html>
</richcontent>
</node>
<node CREATED="1697985096625" ID="ID_1387570892" MODIFIED="1698019077986" TEXT="SPINTIME">
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<head>
</head>
<body>
<p>
awaiting imminent activities
</p>
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</richcontent>
</node>
<node CREATED="1697985096625" ID="ID_1218749290" MODIFIED="1698019089902" TEXT="NEARTIME">
<richcontent TYPE="NOTE"><html>
<head>
</head>
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<p>
capacity for active processing required
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<head>
</head>
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<p>
typical stable work task rhythm expected
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<head>
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<p>
time to go to sleep
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@ -82517,6 +82631,10 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
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