void
allocate_page(void)
{
int req_pageno = vmem->adm.req_pageno;
int frame = VOID_IDX;
int page_removed_idx = VOID_IDX;
if(vmem->pt.entries[req_pageno].flags & PTF_PRESENT)
{
// no page fault!
return;
}
/* find free page */
frame = search_bitmap();
#ifdef DEBUG_MESSAGES
printf("bitmap: frame %d\n", frame);
#endif // DEBUG_MESSAGES
if(frame != VOID_IDX)
{
fprintf(stderr, "Found free frame no %d, allocation page\n", frame);
update_pt(frame);
fetch_page(vmem->adm.req_pageno);
} else {
frame = find_remove_frame();
}
/* TODO: impl stuff*/
page_removed_idx = vmem->pt.framepage[frame];
/* TODO: impl stuff*/
/* Store page to be removed and clear present-bit */
if(vmem->pt.entries[page_removed_idx].flags & PTF_DIRTY) {
store_page(page_removed_idx);
}
vmem->pt.entries[page_removed_idx].flags &= ~PTF_PRESENT;
/* Load new page */
update_pt(frame);
fetch_page(vmem->adm.req_pageno);
/* Update page fault counter */
vmem->adm.pf_count++;
// log allocation
struct logevent le;
le.req_pageno = vmem->adm.req_pageno;
le.replaced_page = page_removed_idx;
le.alloc_frame = frame;
le.pf_count = vmem->adm.pf_count;
le.g_count = vmem->adm.g_count;
logger(le);
// unblock application
sem_post(&(vmem->adm.sema));
}
static int toss_page()
{
int page;
int frame;
page = get_removal_page();
if (!pg_table[page].valid) {
fprintf(stderr, "toss_page: tossing invalid page\n");
return -1;
}
if (page < 0) {
fprintf(stderr, "toss_page: all valid pages in use. Increase page size or physical memory.\n");
return -1;
}
store_page(page);
pg_table[page].valid = 0;
frame = pg_table[page].frame_addr / sys_pager.pg_size;
free_frames[frame] = 1;
return 0;
}
void update_pt(int frame) {
int mBit; //mod bit
int pagenumb = vmem->adm.req_pageno;
// alte Seite aus dem Frame löschen
int oldPage = vmem->pt.framepage[frame];
event.replaced_page=oldPage;
if(oldPage != VOID_IDX){
vmem->pt.entries[oldPage].frame = VOID_IDX;
}
// die Seite in File schreiben, wenn notwendig
mBit = vmem->pt.entries[oldPage].flags & PTF_DIRTY;
if (oldPage != VOID_IDX && mBit == PTF_DIRTY) {
store_page(oldPage);
vmem->pt.entries[oldPage].flags -= PTF_DIRTY;
}
//neue Seite laden
fetch_page(pagenumb);
vmem->pt.entries[pagenumb].frame = frame;
vmem->pt.entries[pagenumb].age=DEF_AGE;
vmem->pt.framepage[frame] = pagenumb;
}
void page_fault() {
int page_unloaded = VOID_IDX;
int new_frame = VOID_IDX;
int req_page = vmem->adm.req_pageno;
// Page fault aufgetreten
DEBUG(fprintf(stderr, "Pagefault: Requested Page: %d\n", req_page));
vmem->adm.pf_count++;
new_frame = find_remove_frame();
page_unloaded = vmem->pt.framepage[new_frame];
if( vmem_is_full() ) {
store_page(page_unloaded);
}
update_pt(new_frame);
fetch_page(req_page);
// make Logs
struct logevent le;
le.req_pageno = vmem->adm.req_pageno;
le.replaced_page = page_unloaded;
le.alloc_frame = new_frame;
le.pf_count = vmem->adm.pf_count;
le.g_count = vmem->adm.pf_count;
logger(le);
DEBUG(fprintf(stderr, "Page loaded. pf_count=%d\n", vmem->adm.pf_count));
// Den aufrufenden Freigeben
sem_post(&vmem->adm.sema);
}
