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physmem.c: align memory to word and page size

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- physmem.c (align_sbrk): align the end of the data segment
- physmem.c (calloc_phys_vec): align the line pointer vector to a machine
  word, just in case
- physmem.c (calloc_phys_vec): crudely align the line buffers within
  pages, to avoid page-crossing within a line (yes, this does reduce
  noise)
This commit is contained in:
Werner Almesberger 2011-04-29 13:58:02 -03:00
parent 2cee702ff4
commit debe9cc351
1 changed files with 12 additions and 0 deletions
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12
ubb-vga/physmem.c
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@ -21,13 +21,25 @@
*/ */
static void align_brk(int alignment)
{
unsigned long addr;
addr = (unsigned long) sbrk(0);
sbrk(alignment-(addr % alignment));
}
void **calloc_phys_vec(size_t n, size_t size) void **calloc_phys_vec(size_t n, size_t size)
{ {
void **vec; void **vec;
int i; int i;
align_brk(sizeof(void *));
vec = sbrk(sizeof(void *)*n); vec = sbrk(sizeof(void *)*n);
for (i = 0; i != n; i++) { for (i = 0; i != n; i++) {
align_brk(512); /* crude page alignment */
vec[i] = sbrk(size); vec[i] = sbrk(size);
memset(vec[i], 0, size); memset(vec[i], 0, size);
} }