Software architecture design

Architecture

Producer / Consumer

• One Producer instance per CPU
• One Consumer instance per CPU

Client / Server

• One server daemon process
• Many client processes

Instructions

• Producer
  One kernel thread bound to a CPU id.
  Cycle_<ArchName>() functions defined in intelfreq.c

• Consumer
  One user-space thread bound to the same CPU id.
  Core_Cycle() function defined in intelfreq.c

• Time division
  A single timer which periodically notifies the kernel threads to start execution.
  Cycle_Timer() function defined in intelfreq.c

• Priority
  1- kernel thread executes first,
  2- user-space thread executes next.

Data

• Producer
  One private data allocated memory per kernel thread.
  KPRIVATE{} structure defined in intelfreq.h

  One public data allocated memory per kernel thread, shared between the kernel thread and the server thread.
  KPUBLIC{} structure defined in intelfreq.h

  A global data allocated memory shared between the kernel process and the server process.
  PROC{} structure defined in intelapi.h

• Consumer
  One public data allocated memory per server thread shared with the client processes.
  CPU_STRUCT{} structure defined in corefreq.h

  A global data allocated memory shared between the server and the client processes.
  PROC_STRUCT{} structure defined in corefreq.h

• Server & Clients A data memory space of shared pointers between the server and the client processes.
  SHM_STRUCT{} structure defined in corefreq.h

Algorithm:

1- Kernel thread waits for a completion synchronization in Cycle_<ArchName>() functions.

Cycle_<ArchName>() { wait_for_completion_timeout(&KPrivate->Join[cpu]->Elapsed) }

2- timer wakes all kernel threads up through their private completion variable
hrtimer_restart() { /* for all CPU */ complete(&KPrivate->Join[cpu]->Elapsed) /* then rearm the timer for a future interruption */ hrtimer_forward() }

3- each kernel thread reads some Core data, such as:
counters state.
Counters_<ArchName>()
temperature
Core_Thermal()

• updates the public kernel data structure.
  CORE{} structure defined in intelapi.h
• synchronizes with the user-space thread.
  BITSET(Core->Sync.V, 0)

4. each server thread waits to start execution in Core_Cycle()

• sleeps and periodically watches for a kernel synchronization change.
  while(!BITWISEAND(Core->Sync.V, 0x1)) usleep(Proc->msleep * 100)
• resets the kernel synchronization variable.
  BITCLR(Core->Sync.V, 0)
• checks if the server thread associated room bit is set
  ---> if yes then selects an alternated flip-flop data memory.
  Cpu->Toggle =! Cpu->Toggle
  then clear the room bit.
  BITCLR(Proc->Room, cpu)
  ---> if no, so keeps the current flip-flop data memory.
• computes some CPU ratios from the public kernel thread data structure.
  CORE{}
• fills the selected flip-flop data structure with the computed ratios.
  FLIP_FLOP{} sub-structure of CPU_STRUCT{} defined in corefreq.h
• loops back to the waiting point.

5. server thread waits to start execution in Proc_Cycle()

• sleeps until all room bits are cleared. while(BITWISEAND(Shm->Proc.Room,roomSeed)) usleep(Shm->Proc.msleep * 100);
• for each CPU alternate flip-flop data structure, sums the ratios.
• sets all room bits to one.
• computes the average ratios.
• synchronize with the client processes.
  BITSET(Shm->Proc.Sync, 0)
• loops back to the waiting point.

6. client process waits to start execution in corefreq-cli.c

• sleeps and periodically watches for a server synchronization change.
  while(!BITWISEAND(Shm->Proc.Sync, 0x1) && !Shutdown) usleep(Shm->Proc.msleep * 100); BITCLR(Shm->Proc.Sync, 0);
• displays per CPU ratios and Processor average ratios
• loops back to the waiting point.