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[kernel] Give scheduler better history tracking

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The scheduler again tracks remaining timeslice. Timeslices are bigger,
but once a process uses all of its timeslice, it's demoted and
replenished at the next priority. The scheduler also tracks the last
time a process ran, and promotes it if it's been starved for twice its
full timeslice.

TODO: replenish a small amount of timeslice each time a process is run,
so that more interactive processes keep their priorities.
This commit is contained in:
Justin C. Miller
2020-06-05 00:15:03 -07:00
parent a10aca573d
commit b4adc29d7f
5 changed files with 58 additions and 30 deletions
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12
src/kernel/scheduler.h
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@@ -18,12 +18,20 @@ extern "C" void task_fork(process *child);
class scheduler
{
public:
/// Total number of priority levels
static const uint8_t num_priorities = 8;
/// Maximum (least urgent/interactive) priority
static const uint8_t max_priority = num_priorities - 1;
static const uint8_t default_priority = num_priorities / 2;
/// Default priority on process creation
static const uint8_t default_priority = 1;
/// Loest (most urgent) priority achieved via promotion
static const uint8_t promote_limit = 1;
/// How long the base timer quantum is, in us
static const uint64_t quantum_micros = 5000;
static const uint64_t quantum_micros = 500;
/// How many quanta a process gets before being rescheduled
static const uint16_t process_quanta = 10;