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Eliminate some vm object relocks in vm fault.

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For the vm_fault_prefault() call from vm_fault_soft_fast(), extend the
scope of the object rlock to avoid re-taking it inside
vm_fault_prefault(). It causes pmap_enter_quick() sometimes called
with shadow object lock as well as the page lock, but this looks
innocent.

Noted and measured by:	mjg
Reviewed by:	alc, markj (as part of the larger patch)
Tested by:	pho (as part of the larger patch)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D15122
This commit is contained in:
Konstantin Belousov 2018-04-29 12:43:08 +00:00
parent 41adbaa596
commit a7163bb962
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=333091
1 changed files with 13 additions and 9 deletions
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22
sys/vm/vm_fault.c
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@ -132,7 +132,7 @@ struct faultstate {
static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
int ahead);
static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
int backward, int forward);
int backward, int forward, bool obj_locked);
static inline void
release_page(struct faultstate *fs)
@ -320,9 +320,9 @@ vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
return (rv);
vm_fault_fill_hold(m_hold, m);
vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false);
VM_OBJECT_RUNLOCK(fs->first_object);
if (psind == 0 && !wired)
vm_fault_prefault(fs, vaddr, PFBAK, PFFOR);
vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true);
VM_OBJECT_RUNLOCK(fs->first_object);
vm_map_lookup_done(fs->map, fs->entry);
curthread->td_ru.ru_minflt++;
return (KERN_SUCCESS);
@ -1262,7 +1262,7 @@ RetryFault:;
wired == 0)
vm_fault_prefault(&fs, vaddr,
faultcount > 0 ? behind : PFBAK,
faultcount > 0 ? ahead : PFFOR);
faultcount > 0 ? ahead : PFFOR, false);
VM_OBJECT_WLOCK(fs.object);
vm_page_lock(fs.m);
@ -1395,7 +1395,7 @@ vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
*/
static void
vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
int backward, int forward)
int backward, int forward, bool obj_locked)
{
pmap_t pmap;
vm_map_entry_t entry;
@ -1441,7 +1441,8 @@ vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
lobject = entry->object.vm_object;
VM_OBJECT_RLOCK(lobject);
if (!obj_locked)
VM_OBJECT_RLOCK(lobject);
while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
lobject->type == OBJT_DEFAULT &&
(backing_object = lobject->backing_object) != NULL) {
@ -1449,17 +1450,20 @@ vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
0, ("vm_fault_prefault: unaligned object offset"));
pindex += lobject->backing_object_offset >> PAGE_SHIFT;
VM_OBJECT_RLOCK(backing_object);
VM_OBJECT_RUNLOCK(lobject);
if (!obj_locked || lobject != entry->object.vm_object)
VM_OBJECT_RUNLOCK(lobject);
lobject = backing_object;
}
if (m == NULL) {
VM_OBJECT_RUNLOCK(lobject);
if (!obj_locked || lobject != entry->object.vm_object)
VM_OBJECT_RUNLOCK(lobject);
break;
}
if (m->valid == VM_PAGE_BITS_ALL &&
(m->flags & PG_FICTITIOUS) == 0)
pmap_enter_quick(pmap, addr, m, entry->protection);
VM_OBJECT_RUNLOCK(lobject);
if (!obj_locked || lobject != entry->object.vm_object)
VM_OBJECT_RUNLOCK(lobject);
}
}