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+ Current setup will likely not last long, just a stopgap until I figure
out how I want to build each testcase etc.
Probably dir based, but I'll probably add some scripts that generate
the build rules for each test case (or binary?). Also, should probably
put ouput files in a build directory and keep the source clean, but
again, good enough for now.
Will have to start implementing more extensive tests, and probably
come up with some way to compare textual output etc.
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+ A reserved area is an area at the start of the region that should not
be used unless explicitly asked for, for example null pages.
As such, a small correction to my previous commit message: There's no
danger in not locking req_mem() etc, as a null page will only be
allocated when explicitly asked for.
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+ User has to 'free' the 0 page before it becomes accessible to mapping.
Probably worth noting that this is likely VERY niche and mainly
concerns stuff like certain kinds of emulators that I'm still
eons from implementing, but still.
Unbacked pages can also be useful for some kinds of notifications,
like 'if someone writes to this page, please report it to me with this
ID' or whatever, I remember seeing some discussion about it somewhere
but that's also not really relevant for the moment.
Most significantly, at least with the current design,
after the null page is freed it becomes available for use to regular req_mem()
calls, so users should probably using locks around memory requests.
That's probably a good idea anyway as internally the kernal has to
lock the virtual memory, and without a scheduler it might cause
threads to spin for a while in the kernel which is rather bad.
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+ Can be used to pass contiguous memory regions to things like virtio
block devices for implementing disk drivers etc.
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+ Effectively means that all executables can be called into, but if an
exe doesn't want to deal with anyone else it should just set a flag
like `not_really_a_server` or whatever
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+ Had some minor issues with a wraparound of size_t that effectively
meant that some regions were allocated twice. Also, booting should be
a bit more reliable now, turned out that the previous iteration of the
booting was just accidentally working due to the kernel being placed
'close enough' in RAM to where it was linked to. Fixed by allocating a
vmem of O1 that maps the kernel to a 2MiB boundary at boot, pretty
nifty.
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+ Slightly more overhead but will help track down possible memory leaks
in the future. Could also add in a flag for turning off/on but I don't
think the difference in performance is that significant.
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+ The system is now a bit simpler and hopefully easier to understand, while also
extending the shared memory to be 1:N, where there is one owner who
may become a zombie while waiting for the N to die.
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+ Still largely untested, should really try to come up with a proper
testsuite, at the moment it's mostly me trying things out in the (as
of yet unreleased) kmx repo
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+ Terminology is still a bit poor, and will still have to write
documentation + implement ipis properly
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+ The number of allowed threads running at the same time is limited to
num_tids, but each thread's ID can be any larger than that. This
should make ID reuse a lot more rare, and probably makes certain kinds
of time-of-check-to-time-of-use attacks more difficult
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+ Found it in newlib. This allows the compiler to more effectively
optimize away unnecessary register operations. Applied to both kernel
and init.c for a slight speed increase.
I really should move init.c to some other repository though, the
binary files are starting to get annoying
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+ Try to write arguments to memory as fast as possible to free up some
registers that the compiler can then play with.
Qemu runs ~1 700 000 rpc's per second, visionfive2 @1GHz (I think) ~800 000.
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+ Now 10M alloc/frees succeed, which totals more memory than the virtual
machine has, so no too obvious leaks are occuring. For future
debugging speed, changed 10M to 1M.
+ Also quick fix to rpcs, stacks are now assigned. Not entirely sure why
they worked before this, but good that I found it.
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+ Both easier to look at and now the userspace doesn't play as big of a
role in the 'benchmarking' with optimizations turned on.
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+ Not strictly done yet, but we can swap between two processes :D
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+ Not actually working (at least fully), need to continue debugging when
I have time.
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+ In total, a syscall is built up of 6 values, with the first being the
syscall number. Symmetrically, the first value is now a status and the
following five values return "values". This allows us to cram in more
info into the ipc_* functions. The performance difference is
absolutely minimal, at least from my testing in qemu.
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