svn commit: r327468 - head/sys/vm

[Konstantin Belousov]

Author: kib
Date: Mon Jan  1 19:27:33 2018
New Revision: 327468
URL: https://svnweb.freebsd.org/changeset/base/327468

Log:
  Do not let vm_daemon run unbounded.
  
  On a load where single anonymous object consumes almost all memory on
  the large system, swapout code executes the iteration over the
  corresponding object page queue for long time, owning the map and
  object locks.  This blocks pagedaemon which tries to lock the object,
  and blocks other threads in the process in vm_fault() waiting for the
  map lock.
  
  Handle the issue by terminating the deactivation loop if we executed
  too long and by yielding at the top level in vm_daemon.
  
  Reported by:	peterj, pho
  Reviewed by:	alc
  Tested by:	pho (as part of the larger patch)
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week
  Differential revision:	https://reviews.freebsd.org/D13671

Modified:
  head/sys/vm/vm_swapout.c

Modified: head/sys/vm/vm_swapout.c
==============================================================================
--- head/sys/vm/vm_swapout.c	Mon Jan  1 19:04:40 2018	(r327467)
+++ head/sys/vm/vm_swapout.c	Mon Jan  1 19:27:33 2018	(r327468)
@@ -203,6 +203,8 @@ vm_swapout_object_deactivate_pages(pmap_t pmap, vm_obj
 		TAILQ_FOREACH(p, &object->memq, listq) {
 			if (pmap_resident_count(pmap) <= desired)
 				goto unlock_return;
+			if (should_yield())
+				goto unlock_return;
 			if (vm_page_busied(p))
 				continue;
 			VM_CNT_INC(v_pdpages);
@@ -516,8 +518,10 @@ again:
 			PRELE(p);
 		}
 		sx_sunlock(&allproc_lock);
-		if (tryagain != 0 && attempts <= 10)
+		if (tryagain != 0 && attempts <= 10) {
+			maybe_yield();
 			goto again;
+		}
 	}
 }