Hardware Reference
In-Depth Information
Table 5.13
Components of HIGHMEM framework
Physical page allocation
Allocates a physical page at the kernel call
HIGHMEM area allocation
Allocates a virtual address for HIGHMEM
Memory access
Accesses a virtual address allocated in a previous access
Update PTE
Registers the combination of a virtual address and
physical address to a PTE
Resolve TLB miss
When a memory access violation has occurred, it
obtains the combination of the virtual address
(missed address) and physical address from the
PTE, and updates the TLB
PTE (page table entry)
Software table for translation between the physical
address and the virtual address
TLB (translation look-aside buffer)
Hardware table for translation between the physical
address and the virtual address
Table 5.14
Software version
Version number
miss resolver calls the physical page allocator and calculates the physical address
from the TLB-missed virtual address and the PTE in step (4). In step (6), the TLB
miss resolver registers the combination of the virtual address and physical address
to the TLB.
As just described, the HIGHMEM feature implemented by the Linux kernel
saves the combination of the physical address (over 32 bits) and the virtual address
(under 32 bits) as the PTE, and the TLB is updated when a memory access violation
occurs (Table 5.13 ).
Our HIGHMEM framework was evaluated to determine whether the existing appli-
cations and driver could be run without any modifications. The Linux version on
which we have extended the HIGHMEM framework is shown in the following table
(Table 5.14 ).
To evaluate the application's compatibility, LMBench and IOzone [ 9 ] are used
for testing. Both benchmarks are suitable for verifying that Linux runs correctly.
Development tools like the cross compiler and cross linker are also tested using
these benchmarks.
To maintain compatibility between drivers, none of the devices for RP-X needed
changes in their drivers' source code except for the serial-ATA driver, which needed
a change in the DMA access function. This is because the RP-X's serial-ATA device
Search WWH ::

Custom Search