From d966c7615f74abea52e6f12981f93f16c5b4d421 Mon Sep 17 00:00:00 2001 From: Jeff Roberson Date: Sun, 15 Dec 2019 02:02:27 +0000 Subject: [PATCH] Slightly optimize locking in vm_map_copy_swap_entry(). Anonymous objects require the object lock to synchronize collapse. Other swap objects such as tmpfs do not. Reported by: mjg Reviewed by: kib, markj Differential Revision: https://reviews.freebsd.org/D22747 --- sys/vm/vm_map.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c index 4c5441909ad8..74846e9a0fc7 100644 --- a/sys/vm/vm_map.c +++ b/sys/vm/vm_map.c @@ -3870,15 +3870,19 @@ vm_map_copy_swap_object(vm_map_entry_t src_entry, vm_map_entry_t dst_entry, int charged; src_object = src_entry->object.vm_object; - VM_OBJECT_WLOCK(src_object); charged = ENTRY_CHARGED(src_entry); - vm_object_collapse(src_object); - if ((src_object->flags & OBJ_ONEMAPPING) != 0) { - vm_object_split(src_entry); - src_object = src_entry->object.vm_object; - } - vm_object_reference_locked(src_object); - vm_object_clear_flag(src_object, OBJ_ONEMAPPING); + if ((src_object->flags & OBJ_ANON) != 0) { + VM_OBJECT_WLOCK(src_object); + vm_object_collapse(src_object); + if ((src_object->flags & OBJ_ONEMAPPING) != 0) { + vm_object_split(src_entry); + src_object = src_entry->object.vm_object; + } + vm_object_reference_locked(src_object); + vm_object_clear_flag(src_object, OBJ_ONEMAPPING); + VM_OBJECT_WUNLOCK(src_object); + } else + vm_object_reference(src_object); if (src_entry->cred != NULL && !(src_entry->eflags & MAP_ENTRY_NEEDS_COPY)) { KASSERT(src_object->cred == NULL, @@ -3887,7 +3891,6 @@ vm_map_copy_swap_object(vm_map_entry_t src_entry, vm_map_entry_t dst_entry, src_object->cred = src_entry->cred; src_object->charge = size; } - VM_OBJECT_WUNLOCK(src_object); dst_entry->object.vm_object = src_object; if (charged) { cred = curthread->td_ucred;