Now that operations on amaps are serialized using a per-map rwlock
the KERNEL_LOCK() shouldn't be necessary to call amap_unref(). The
diff below allows the reaper to do this operation before grabbing it.
I haven't seen any relevant contention on the reaper in my profilings,
so I don't expect any visible change related to this change. However
this reflects the current state of locking in UVM and helps me shrink
my diff.
ok?
Index: uvm/uvm_map.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_map.c,v
retrieving revision 1.275
diff -u -p -r1.275 uvm_map.c
--- uvm/uvm_map.c 22 May 2021 08:38:29 -0000 1.275
+++ uvm/uvm_map.c 14 Jun 2021 09:32:04 -0000
@@ -1571,10 +1571,16 @@ uvm_unmap_detach(struct uvm_map_deadq *d
TAILQ_FOREACH_SAFE(entry, deadq, dfree.deadq, tmp) {
/* Skip entries for which we have to grab the kernel lock. */
- if (entry->aref.ar_amap || UVM_ET_ISSUBMAP(entry) ||
- UVM_ET_ISOBJ(entry))
+ if (UVM_ET_ISSUBMAP(entry) || UVM_ET_ISOBJ(entry))
continue;
+ /* Drop reference to amap, if we've got one. */
+ if (entry->aref.ar_amap)
+ amap_unref(entry->aref.ar_amap,
+ entry->aref.ar_pageoff,
+ atop(entry->end - entry->start),
+ flags & AMAP_REFALL);
+
TAILQ_REMOVE(deadq, entry, dfree.deadq);
uvm_mapent_free(entry);
}
@@ -1586,12 +1592,6 @@ uvm_unmap_detach(struct uvm_map_deadq *d
while ((entry = TAILQ_FIRST(deadq)) != NULL) {
if (waitok)
uvm_pause();
- /* Drop reference to amap, if we've got one. */
- if (entry->aref.ar_amap)
- amap_unref(entry->aref.ar_amap,
- entry->aref.ar_pageoff,
- atop(entry->end - entry->start),
- flags & AMAP_REFALL);
/* Drop reference to our backing object, if we've got one. */
if (UVM_ET_ISSUBMAP(entry)) {
