Invalidations are not done if mapping or unmapping previously unmapped
page. TLB invalidate IPIs are now ignored if they don't affect the
currently mapped address space
This was causing some kernel panic because processors ran out of smp
message storage when reserving large areas.
Also most of the time there is no need to actually send the SMP message.
If process is mapping something to just its own address space, there is
no need for a TLB shootdown. Maybe this should be only limited to kernel
memory and threads across the same process. I'm not sure what the best
approach here and it is better to send too many invalidations that too
few!
Before I assumed that bootloaders loaded the kernel at physical address
0, but this patch kinda allows loading to different addresses. This
still doesn't fully work as kernel bootstrap paging relies on kernel
being loaded at 0
Change Semaphore -> ThreadBlocker
This was not a semaphore, I just named it one because I didn't know
what semaphore was. I have meant to change this sooner, but it was in
no way urgent :D
Implement SMP events. Processors can now be sent SMP events through
IPIs. SMP events can be sent either to a single processor or broadcasted
to every processor.
PageTable::{map_page,map_range,unmap_page,unmap_range}() now send SMP
event to invalidate TLB caches for the changed pages.
Scheduler no longer uses a global run queue. Each processor has its own
scheduler that keeps track of the load on the processor. Once every
second schedulers do load balancing. Schedulers have no access to other
processors' schedulers, they just see approximate loads. If scheduler
decides that it has too much load, it will send a thread to another
processor through a SMP event.
Schedulers are currently run using the timer interrupt on BSB. This
should be not the case, and each processor should use its LAPIC timer
for interrupts. There is no reason to broadcast SMP event to all
processors when BSB gets timer interrupt.
Old scheduler only achieved 20% idle load on qemu. That was probably a
very inefficient implementation. This new scheduler seems to average
around 1% idle load. This is much closer to what I would expect. On my
own laptop idle load seems to be only around 0.5% on each processor.
Add "fast page" to KERNEL_OFFSET. This is always present in page
tables and only requires changing the page table entry to map. This
requires no interrupts since it should only be for very operations
like memcpy.
I used to map all temporary mappings to vaddr 0, but this is much
better. C++ standard always says that nullptr access is undefined
and this gets rid of it.
Fixed some bugs I found along the way
Allocations bigger than PAGE_SIZE and those not forced to be identity
mapped are now done on a GeneralAllocator. This allows us to use kmalloc
for big allocations; bigger than the fixed 1 MiB storage.
This is still a hack and the whole kmalloc will have to be rewritten at
some point, but for now this does the job :D
