Significantly simplify the fault clustering code. After some analysis by
David Greenman, it has been determined that the more sophisticated code only made a very minor difference in fault performance. Therefore, this code eliminates some of the complication of the fault code, decreasing the amount of CPU used to scan shadow chains.
This commit is contained in:
John Dyson
parent
aca3622c3f
commit
22ba64e870
@ -66,7 +66,7 @@
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*
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* $Id: vm_fault.c,v 1.30 1995/09/11 00:45:15 dyson Exp $
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* $Id: vm_fault.c,v 1.31 1995/09/14 13:42:52 dyson Exp $
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*/
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/*
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@ -88,7 +88,7 @@
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#include <vm/vm_pager.h>
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#include <vm/vnode_pager.h>
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int vm_fault_additional_pages __P((vm_object_t, vm_offset_t, vm_page_t, int, int, vm_page_t *, int *));
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int vm_fault_additional_pages __P((vm_page_t, int, int, vm_page_t *, int *));
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#define VM_FAULT_READ_AHEAD 4
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#define VM_FAULT_READ_BEHIND 3
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@ -184,8 +184,9 @@ RetryFault:;
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* search.
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*/
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if ((result = vm_map_lookup(&map, vaddr, fault_type, &entry, &first_object,
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&first_offset, &prot, &wired, &su)) != KERN_SUCCESS) {
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if ((result = vm_map_lookup(&map, vaddr,
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fault_type, &entry, &first_object,
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&first_offset, &prot, &wired, &su)) != KERN_SUCCESS) {
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return (result);
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}
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@ -269,17 +270,18 @@ RetryFault:;
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goto RetryFault;
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}
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if ((m->flags & PG_CACHE) &&
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(cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_reserved) {
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UNLOCK_AND_DEALLOCATE;
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VM_WAIT;
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goto RetryFault;
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}
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/*
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* Mark page busy for other processes, and the pagedaemon.
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*/
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m->flags |= PG_BUSY;
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if ((m->flags & PG_CACHE) &&
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(cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_reserved) {
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UNLOCK_AND_DEALLOCATE;
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VM_WAIT;
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PAGE_WAKEUP(m);
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goto RetryFault;
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}
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if (m->valid && ((m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) &&
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m->object != kernel_object && m->object != kmem_object) {
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goto readrest;
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@ -293,20 +295,7 @@ RetryFault:;
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UNLOCK_AND_DEALLOCATE;
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return (KERN_PROTECTION_FAILURE);
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}
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#if 0 /* XXX is this really necessary? */
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if (swap_pager_full && !object->backing_object &&
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(object->type == OBJT_DEFAULT ||
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(object->type == OBJT_SWAP &&
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!vm_pager_has_page(object, offset + object->paging_offset, NULL, NULL)))) {
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if (vaddr < VM_MAXUSER_ADDRESS && curproc && curproc->p_pid >= 48) { /* XXX */
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printf("Process %lu killed by vm_fault -- out of swap\n", (u_long) curproc->p_pid);
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psignal(curproc, SIGKILL);
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curproc->p_estcpu = 0;
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curproc->p_nice = PRIO_MIN;
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resetpriority(curproc);
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}
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}
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#endif
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/*
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* Allocate a new page for this object/offset pair.
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*/
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@ -338,7 +327,6 @@ RetryFault:;
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* vm_page_t passed to the routine.
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*/
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faultcount = vm_fault_additional_pages(
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first_object, first_offset,
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m, VM_FAULT_READ_BEHIND, VM_FAULT_READ_AHEAD,
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marray, &reqpage);
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@ -351,6 +339,7 @@ RetryFault:;
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rv = faultcount ?
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vm_pager_get_pages(object, marray, faultcount,
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reqpage) : VM_PAGER_FAIL;
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if (rv == VM_PAGER_OK) {
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/*
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* Found the page. Leave it busy while we play
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@ -370,6 +359,7 @@ RetryFault:;
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pmap_clear_modify(VM_PAGE_TO_PHYS(m));
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m->valid = VM_PAGE_BITS_ALL;
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m->flags |= PG_BUSY;
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hardfault++;
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break;
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}
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@ -669,6 +659,8 @@ RetryFault:;
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}
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}
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if ((m->flags & PG_BUSY) == 0)
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printf("page not busy: %d\n", m->offset);
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/*
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* Unlock everything, and return
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*/
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@ -860,49 +852,13 @@ vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry)
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}
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/*
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* looks page up in shadow chain
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*/
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int
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vm_fault_page_lookup(object, offset, rtobject, rtoffset, rtm)
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vm_object_t object;
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vm_offset_t offset;
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vm_object_t *rtobject;
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vm_offset_t *rtoffset;
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vm_page_t *rtm;
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{
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vm_page_t m;
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*rtm = 0;
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*rtoffset = 0;
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while (!(m = vm_page_lookup(object, offset))) {
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if (vm_pager_has_page(object,
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object->paging_offset + offset, NULL, NULL)) {
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*rtobject = object;
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*rtoffset = offset;
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return 1;
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}
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if (!object->backing_object || (object == *rtobject))
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return 0;
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else {
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offset += object->backing_object_offset;
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object = object->backing_object;
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}
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}
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*rtobject = object;
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*rtoffset = offset;
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*rtm = m;
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return 1;
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}
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/*
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* This routine checks around the requested page for other pages that
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* might be able to be faulted in.
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* might be able to be faulted in. This routine brackets the viable
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* pages for the pages to be paged in.
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*
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* Inputs:
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* first_object, first_offset, m, rbehind, rahead
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* m, rbehind, rahead
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*
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* Outputs:
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* marray (array of vm_page_t), reqpage (index of requested page)
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@ -911,31 +867,23 @@ vm_fault_page_lookup(object, offset, rtobject, rtoffset, rtm)
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* number of pages in marray
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*/
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int
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vm_fault_additional_pages(first_object, first_offset, m, rbehind, raheada, marray, reqpage)
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vm_object_t first_object;
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vm_offset_t first_offset;
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vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
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vm_page_t m;
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int rbehind;
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int raheada;
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int rahead;
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vm_page_t *marray;
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int *reqpage;
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{
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int i;
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vm_object_t object;
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vm_offset_t offset, startoffset, endoffset, toffset, size;
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vm_object_t rtobject;
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vm_page_t rtm;
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vm_offset_t rtoffset;
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vm_offset_t offsetdiff;
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int rahead;
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int treqpage;
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int cbehind, cahead;
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object = m->object;
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offset = m->offset;
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offsetdiff = offset - first_offset;
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/*
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* if the requested page is not available, then give up now
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*/
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@ -944,55 +892,48 @@ vm_fault_additional_pages(first_object, first_offset, m, rbehind, raheada, marra
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object->paging_offset + offset, &cbehind, &cahead))
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return 0;
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if (object->backing_object == NULL) {
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if (raheada > cahead) {
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raheada = cahead;
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}
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if (rbehind > cbehind) {
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rbehind = cbehind;
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}
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if ((cbehind == 0) && (cahead == 0)) {
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*reqpage = 0;
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marray[0] = m;
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return 1;
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}
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if (rahead > cahead) {
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rahead = cahead;
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}
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if (rbehind > cbehind) {
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rbehind = cbehind;
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}
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/*
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* try to do any readahead that we might have free pages for.
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*/
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rahead = raheada;
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if ((rahead + rbehind) >
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((cnt.v_free_count + cnt.v_cache_count) - 2*cnt.v_free_reserved)) {
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rahead = ((cnt.v_free_count + cnt.v_cache_count) -
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2*cnt.v_free_reserved) / 2;
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rbehind = rahead;
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if (!rahead)
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pagedaemon_wakeup();
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}
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/*
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* if we don't have any free pages, then just read one page.
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*/
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if (rahead <= 0) {
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((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) {
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pagedaemon_wakeup();
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*reqpage = 0;
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marray[0] = m;
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return 1;
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}
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/*
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* scan backward for the read behind pages -- in memory or on disk not
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* in same object
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*/
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toffset = offset - NBPG;
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toffset = offset - PAGE_SIZE;
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if (toffset < offset) {
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if (rbehind * NBPG > offset)
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rbehind = offset / NBPG;
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startoffset = offset - rbehind * NBPG;
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if (rbehind * PAGE_SIZE > offset)
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rbehind = offset / PAGE_SIZE;
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startoffset = offset - rbehind * PAGE_SIZE;
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while (toffset >= startoffset) {
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rtobject = object;
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if (!vm_fault_page_lookup(first_object,
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toffset - offsetdiff, &rtobject, &rtoffset, &rtm) ||
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rtm != 0 || rtobject != object) {
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startoffset = toffset + NBPG;
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if (vm_page_lookup( object, toffset)) {
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startoffset = toffset + PAGE_SIZE;
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break;
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}
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if (toffset == 0)
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break;
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toffset -= NBPG;
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toffset -= PAGE_SIZE;
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}
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} else {
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startoffset = offset;
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@ -1002,34 +943,35 @@ vm_fault_additional_pages(first_object, first_offset, m, rbehind, raheada, marra
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* scan forward for the read ahead pages -- in memory or on disk not
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* in same object
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*/
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toffset = offset + NBPG;
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endoffset = offset + (rahead + 1) * NBPG;
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while (toffset < object->size && toffset < endoffset) {
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rtobject = object;
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if (!vm_fault_page_lookup(first_object,
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toffset - offsetdiff, &rtobject, &rtoffset, &rtm) ||
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rtm != 0 || rtobject != object) {
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toffset = offset + PAGE_SIZE;
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endoffset = offset + (rahead + 1) * PAGE_SIZE;
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if (endoffset > object->size)
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endoffset = object->size;
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while (toffset < endoffset) {
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if ( vm_page_lookup(object, toffset)) {
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break;
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}
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toffset += NBPG;
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}
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toffset += PAGE_SIZE;
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}
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endoffset = toffset;
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/* calculate number of bytes of pages */
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size = (endoffset - startoffset) / NBPG;
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size = (endoffset - startoffset) / PAGE_SIZE;
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/* calculate the page offset of the required page */
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treqpage = (offset - startoffset) / NBPG;
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treqpage = (offset - startoffset) / PAGE_SIZE;
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/* see if we have space (again) */
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if ((cnt.v_free_count + cnt.v_cache_count) > (cnt.v_free_reserved + size)) {
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if ((cnt.v_free_count + cnt.v_cache_count) >
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(cnt.v_free_reserved + size)) {
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/*
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* get our pages and don't block for them
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*/
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for (i = 0; i < size; i++) {
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if (i != treqpage) {
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rtm = vm_page_alloc(object,
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startoffset + i * NBPG, VM_ALLOC_NORMAL);
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startoffset + i * PAGE_SIZE,
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VM_ALLOC_NORMAL);
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if (rtm == NULL) {
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if (i < treqpage) {
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int j;
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