Author: kib Date: Sun Apr 29 12:43:08 2018 New Revision: 333091 URL: https://svnweb.freebsd.org/changeset/base/333091
Log: Eliminate some vm object relocks in vm fault. 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 Modified: head/sys/vm/vm_fault.c Modified: head/sys/vm/vm_fault.c ============================================================================== --- head/sys/vm/vm_fault.c Sun Apr 29 11:46:20 2018 (r333090) +++ head/sys/vm/vm_fault.c Sun Apr 29 12:43:08 2018 (r333091) @@ -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 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 @@ readrest: 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_offs */ 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_offs 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_offs 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); } } _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
