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Date:      Tue, 2 Jul 2019 19:51:41 +0000 (UTC)
From:      Mark Johnston <markj@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r349612 - head/sys/vm
Message-ID:  <201907021951.x62JpfAl018483@repo.freebsd.org>
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Author: markj
Date: Tue Jul  2 19:51:40 2019
New Revision: 349612
URL: https://svnweb.freebsd.org/changeset/base/349612

Log:
  Mark pages allocated from the per-CPU cache.
  
  Only free pages to the cache when they were allocated from that cache.
  This mitigates rapid fragmentation of physical memory seen during
  poudriere's dependency calculation phase.  In particular, pages
  belonging to broken reservations are no longer freed to the per-CPU
  cache, so they get a chance to coalesce with freed pages during the
  break.  Otherwise, the optimized CoW handler may create object
  chains in which multiple objects contain pages from the same
  reservation, and the order in which we do object termination means
  that the reservation is broken before all of those pages are freed,
  so some of them end up in the per-CPU cache and thus permanently
  fragment physical memory.
  
  The flag may also be useful for eliding calls to vm_reserv_free_page(),
  thus avoiding memory accesses for data that is likely not present
  in the CPU caches.
  
  Reviewed by:	alc
  Discussed with:	jeff
  MFC after:	1 week
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D20763

Modified:
  head/sys/vm/vm_page.c
  head/sys/vm/vm_page.h

Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c	Tue Jul  2 19:32:48 2019	(r349611)
+++ head/sys/vm/vm_page.c	Tue Jul  2 19:51:40 2019	(r349612)
@@ -1812,8 +1812,9 @@ vm_page_alloc_domain_after(vm_object_t object, vm_pind
 	if (object != NULL)
 		VM_OBJECT_ASSERT_WLOCKED(object);
 
-again:
+	flags = 0;
 	m = NULL;
+again:
 #if VM_NRESERVLEVEL > 0
 	/*
 	 * Can we allocate the page from a reservation?
@@ -1829,8 +1830,10 @@ again:
 	vmd = VM_DOMAIN(domain);
 	if (object != NULL && vmd->vmd_pgcache != NULL) {
 		m = uma_zalloc(vmd->vmd_pgcache, M_NOWAIT);
-		if (m != NULL)
+		if (m != NULL) {
+			flags |= PG_PCPU_CACHE;
 			goto found;
+		}
 	}
 	if (vm_domain_allocate(vmd, req, 1)) {
 		/*
@@ -1858,10 +1861,8 @@ again:
 	}
 
 	/*
-	 *  At this point we had better have found a good page.
+	 * At this point we had better have found a good page.
 	 */
-	KASSERT(m != NULL, ("missing page"));
-
 found:
 	vm_page_dequeue(m);
 	vm_page_alloc_check(m);
@@ -1869,10 +1870,8 @@ found:
 	/*
 	 * Initialize the page.  Only the PG_ZERO flag is inherited.
 	 */
-	flags = 0;
 	if ((req & VM_ALLOC_ZERO) != 0)
-		flags = PG_ZERO;
-	flags &= m->flags;
+		flags |= (m->flags & PG_ZERO);
 	if ((req & VM_ALLOC_NODUMP) != 0)
 		flags |= PG_NODUMP;
 	m->flags = flags;
@@ -2018,6 +2017,7 @@ vm_page_alloc_contig_domain(vm_object_t object, vm_pin
 	 * Can we allocate the pages without the number of free pages falling
 	 * below the lower bound for the allocation class?
 	 */
+	m_ret = NULL;
 again:
 #if VM_NRESERVLEVEL > 0
 	/*
@@ -2031,7 +2031,6 @@ again:
 		goto found;
 	}
 #endif
-	m_ret = NULL;
 	vmd = VM_DOMAIN(domain);
 	if (vm_domain_allocate(vmd, req, npages)) {
 		/*
@@ -3506,7 +3505,7 @@ vm_page_free_toq(vm_page_t m)
 		return;
 
 	vmd = vm_pagequeue_domain(m);
-	if (m->pool == VM_FREEPOOL_DEFAULT && vmd->vmd_pgcache != NULL) {
+	if ((m->flags & PG_PCPU_CACHE) != 0 && vmd->vmd_pgcache != NULL) {
 		uma_zfree(vmd->vmd_pgcache, m);
 		return;
 	}

Modified: head/sys/vm/vm_page.h
==============================================================================
--- head/sys/vm/vm_page.h	Tue Jul  2 19:32:48 2019	(r349611)
+++ head/sys/vm/vm_page.h	Tue Jul  2 19:51:40 2019	(r349612)
@@ -379,6 +379,7 @@ extern struct mtx_padalign pa_lock[];
  * Page flags.  If changed at any other time than page allocation or
  * freeing, the modification must be protected by the vm_page lock.
  */
+#define	PG_PCPU_CACHE	0x0001		/* was allocated from per-CPU caches */
 #define	PG_FICTITIOUS	0x0004		/* physical page doesn't exist */
 #define	PG_ZERO		0x0008		/* page is zeroed */
 #define	PG_MARKER	0x0010		/* special queue marker page */

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