Title: Nanokernel Footprint Measurement
Description:
This project is designed to characterize the memory requirements of a
nanokernel-only image running on an Atom target.
The project can be built using several configurations:
minimal (a "do nothing" image that has support for few kernel capabilities)
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- Background task is only task in system; no fibers are utilized.
- Background task simply runs an endless loop that increments a global variable.
- No system timer support.
- ISR for the spurious interrupt handling is present.
- IDT and stack memory sizes are very limited.
regular (a "typical" image that has support for some kernel capabilities)
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- As for "minimal" configuration, except as noted below.
- Supports larger IDT and utilizes larger stacks.
- A statically linked dummy ISR is present.
- Background task also starts a fiber.
- Fiber prints a message to the console via printk().
- Supports system timer, along with NANO_TIMER objects.
- Links in support for NANO_SEM objects.
maximal (a "complex" image that has support for many kernel capabilities)
-------
- As for "regular" configuration, except as noted below.
- Supports full IDT and utilizes even larger stacks.
- Background task dynamically links in the dummy ISR, rather than having
it statically linked.
- Fiber prints a message to the console via printf(), rather than printk().
- Links in support for NANO_LIFO, NANO_STACK, and NANO_FIFO objects.
- Adds floating point support (for x87 FPU, including SSE).
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Building and Running Project:
This nanokernel project does not generate any output in the default case
(TEST=min). In the regular case (TEST=reg) and the maximal case (TEST=max),
it outputs to the console. It can be built and executed on QEMU as follows:
make TEST=min qemu (minimal configuration)
make TEST=reg qemu (regular configuration)
make TEST=max qemu (maximal configuration)
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Troubleshooting:
Problems caused by out-dated project information can be addressed by
issuing one of the following commands then rebuilding the project:
make clean # discard results of previous builds
# but keep existing configuration info
or
make pristine # discard results of previous builds
# and restore pre-defined configuration info
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Sample Output:
The resulting image is bootable for all configurations, but produces different
output in each case.
minimal
-------
This configuration does NOT produce any output. To observe its operation,
invoke it using gdb and observe that:
- main() increments "i" each time it loops
- the kernel's timer ISR increments "nanoTicks" on a regular basis
regular
-------
This configuration prints the following message to the console:
Running regular nanokernel configuration
maximal
-------
This configuration prints the following message to the console:
Running maximal nanokernel configuration
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Additional notes:
Various host utilities (such as the Unix "size" utility) can be used to
determine the footprint of the resulting zephyr.elf image.
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