Commit graph

7 commits

Author SHA1 Message Date
Tomas Hruby
6aa26565e6 SMP - Big kernel lock (BKL)
- to isolate execution inside kernel we use a big kernel lock
  implemented as a spinlock

- the lock is acquired asap after entering kernel mode and released as
  late as possible. Only one CPU as a time can execute the core kernel
  code

- measurement son real hw show that the overhead of this lock is close
  to 0% of kernel time for the currnet system

- the overhead of this lock may be as high as 45% of kernel time in
  virtual machines depending on the ratio between physical CPUs
  available and emulated CPUs. The performance degradation is
  significant
2010-09-15 14:10:03 +00:00
Tomas Hruby
62c666566e SMP - We boot APs
- kernel detects CPUs by searching ACPI tables for local apic nodes

- each CPU has its own TSS that points to its own stack. All cpus boot
  on the same boot stack (in sequence) but switch to its private stack
  as soon as they can.

- final booting code in main() placed in bsp_finish_booting() which is
  executed only after the BSP switches to its final stack

- apic functions to send startup interrupts

- assembler functions to handle CPU features not needed for single cpu
  mode like memory barries, HT detection etc.

- new files kernel/smp.[ch], kernel/arch/i386/arch_smp.c and
  kernel/arch/i386/include/arch_smp.h

- 16-bit trampoline code for the APs. It is executed by each AP after
  receiving startup IPIs it brings up the CPUs to 32bit mode and let
  them spin in an infinite loop so they don't do any damage.

- implementation of kernel spinlock

- CONFIG_SMP and CONFIG_MAX_CPUS set by the build system
2010-09-15 14:09:52 +00:00
Kees van Reeuwijk
ed0b81c25c Removed some unused variables and functions. 2010-06-02 19:41:38 +00:00
Tomas Hruby
24764ff47a Fixed ms-based scheduling for legacy timer 2010-05-26 08:20:29 +00:00
Tomas Hruby
451a6890d6 scheduling - time quantum in miliseconds
- Currently the cpu time quantum is timer-ticks based. Thus the
  remaining quantum is decreased only if the processes is interrupted
  by a timer tick. As processes block a lot this typically does not
  happen for normal user processes. Also the quantum depends on the
  frequency of the timer.

- This change makes the quantum miliseconds based. Internally the
  miliseconds are translated into cpu cycles. Everytime userspace
  execution is interrupted by kernel the cycles just consumed by the
  current process are deducted from the remaining quantum.

- It makes the quantum system timer frequency independent.

- The boot processes quantum is loosely derived from the tick-based
  quantas and 60Hz timer and subject to future change

- the 64bit arithmetics is a little ugly, will be changes once we have
  compiler support for 64bit integers (soon)
2010-05-25 08:06:14 +00:00
Tomas Hruby
b90c2d7026 rename of mode/context switching functions
- this patch only renames schedcheck() to switch_to_user(),
  cycles_accounting_stop() to context_stop() and restart() to
  +restore_user_context()

- the motivation is that since the introduction of schedcheck() it has
  been abused for many things. It deserves a better name.  It should
  express the fact that from the moment we call the function we are in
  the process of switching to user.

- cycles_accounting_stop() was originally a single purpose function.
  As this function is called at were convenient places it is used in
  for other things too, e.g. (un)locking the kernel. Thus it deserves
  a better name too.

- using the old name, restart() does not call schedcheck(), however
  calls to restart are replaced by calls to schedcheck()
  [switch_to_user] and it calls restart() [restore_user_context]
2010-05-18 13:00:39 +00:00
Arun Thomas
4ed3a0cf3a Convert kernel over to bsdmake 2010-04-01 22:22:33 +00:00
Renamed from kernel/arch/i386/clock.c (Browse further)