Author: kib
Date: Mon Aug 25 21:21:29 2014
New Revision: 270630
URL: http://svnweb.freebsd.org/changeset/base/270630
Log:
MFC r270011:
Implement 'fast path' for the vm page fault handler.
MFC r270387 (by alc):
Relax one of the conditions for mapping a page on the fast path.
Approved by: re (gjb)
Modified:
stable/10/sys/vm/vm_fault.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/vm/vm_fault.c
==============================================================================
--- stable/10/sys/vm/vm_fault.c Mon Aug 25 21:19:08 2014 (r270629)
+++ stable/10/sys/vm/vm_fault.c Mon Aug 25 21:21:29 2014 (r270630)
@@ -237,6 +237,7 @@ vm_fault_hold(vm_map_t map, vm_offset_t
int hardfault;
struct faultstate fs;
struct vnode *vp;
+ vm_page_t m;
int locked, error;
hardfault = 0;
@@ -290,6 +291,56 @@ RetryFault:;
goto RetryFault;
}
+ if (wired)
+ fault_type = prot | (fault_type & VM_PROT_COPY);
+
+ if (fs.vp == NULL /* avoid locked vnode leak */ &&
+ (fault_flags & (VM_FAULT_CHANGE_WIRING | VM_FAULT_DIRTY)) == 0 &&
+ /* avoid calling vm_object_set_writeable_dirty() */
+ ((prot & VM_PROT_WRITE) == 0 ||
+ fs.first_object->type != OBJT_VNODE ||
+ (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
+ VM_OBJECT_RLOCK(fs.first_object);
+ if ((prot & VM_PROT_WRITE) != 0 &&
+ fs.first_object->type == OBJT_VNODE &&
+ (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0)
+ goto fast_failed;
+ m = vm_page_lookup(fs.first_object, fs.first_pindex);
+ /* A busy page can be mapped for read|execute access. */
+ if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
+ vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
+ goto fast_failed;
+ result = pmap_enter(fs.map->pmap, vaddr, m, prot,
+ fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED :
+ 0), 0);
+ if (result != KERN_SUCCESS)
+ goto fast_failed;
+ if (m_hold != NULL) {
+ *m_hold = m;
+ vm_page_lock(m);
+ vm_page_hold(m);
+ vm_page_unlock(m);
+ }
+ if ((fault_type & VM_PROT_WRITE) != 0 &&
+ (m->oflags & VPO_UNMANAGED) == 0) {
+ vm_page_dirty(m);
+ vm_pager_page_unswapped(m);
+ }
+ VM_OBJECT_RUNLOCK(fs.first_object);
+ if (!wired)
+ vm_fault_prefault(&fs, vaddr, 0, 0);
+ vm_map_lookup_done(fs.map, fs.entry);
+ curthread->td_ru.ru_minflt++;
+ return (KERN_SUCCESS);
+fast_failed:
+ if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
+ VM_OBJECT_RUNLOCK(fs.first_object);
+ VM_OBJECT_WLOCK(fs.first_object);
+ }
+ } else {
+ VM_OBJECT_WLOCK(fs.first_object);
+ }
+
/*
* Make a reference to this object to prevent its disposal while we
* are messing with it. Once we have the reference, the map is free
@@ -300,15 +351,11 @@ RetryFault:;
* truncation operations) during I/O. This must be done after
* obtaining the vnode lock in order to avoid possible deadlocks.
*/
- VM_OBJECT_WLOCK(fs.first_object);
vm_object_reference_locked(fs.first_object);
vm_object_pip_add(fs.first_object, 1);
fs.lookup_still_valid = TRUE;
- if (wired)
- fault_type = prot | (fault_type & VM_PROT_COPY);
-
fs.first_m = NULL;
/*
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