From 9fb7c918ef5229490f91aaa1aa979f4bcd023be9 Mon Sep 17 00:00:00 2001
From: Mark Johnston <markj@FreeBSD.org>
Date: Wed, 21 Aug 2019 20:01:52 +0000
Subject: [PATCH] Remove manual wire_count adjustments from the unmapped mbuf
 code.

The original code came from a desire to minimize the number of updates
to v_wire_count, which prior to r329187 was updated using atomics.
However, there is no significant benefit to batching today, so simply
allocate pages using VM_ALLOC_WIRED and rely on system accounting.

Reviewed by:	jhb
Differential Revision:	https://reviews.freebsd.org/D21323
---
 sys/kern/uipc_mbuf.c | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index 4b97c15856ba..c9f7e4ca01b0 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -1616,22 +1616,18 @@ mb_free_mext_pgs(struct mbuf *m)
 {
 	struct mbuf_ext_pgs *ext_pgs;
 	vm_page_t pg;
-	int wire_adj;
 
 	MBUF_EXT_PGS_ASSERT(m);
 	ext_pgs = m->m_ext.ext_pgs;
-	wire_adj = 0;
 	for (int i = 0; i < ext_pgs->npgs; i++) {
 		pg = PHYS_TO_VM_PAGE(ext_pgs->pa[i]);
 		/*
 		 * Note: page is not locked, as it has no
 		 * object and is not on any queues.
 		 */
-		vm_page_free_toq(pg);
-		wire_adj++;
+		vm_page_unwire_noq(pg);
+		vm_page_free(pg);
 	}
-	if (wire_adj)
-		vm_wire_sub(wire_adj);
 }
 
 static struct mbuf *
@@ -1640,9 +1636,10 @@ m_uiotombuf_nomap(struct uio *uio, int how, int len, int maxseg, int flags)
 	struct mbuf *m, *mb, *prev;
 	struct mbuf_ext_pgs *pgs;
 	vm_page_t pg_array[MBUF_PEXT_MAX_PGS];
-	int error, length, i, needed, wire_adj = 0;
+	int error, length, i, needed;
 	ssize_t total;
-	int pflags = malloc2vm_flags(how) | VM_ALLOC_NOOBJ | VM_ALLOC_NODUMP;
+	int pflags = malloc2vm_flags(how) | VM_ALLOC_NOOBJ | VM_ALLOC_NODUMP |
+	    VM_ALLOC_WIRED;
 
 	/*
 	 * len can be zero or an arbitrary large value bound by
@@ -1676,9 +1673,6 @@ m_uiotombuf_nomap(struct uio *uio, int how, int len, int maxseg, int flags)
 retry_page:
 			pg_array[i] = vm_page_alloc(NULL, 0, pflags);
 			if (pg_array[i] == NULL) {
-				if (wire_adj)
-					vm_wire_add(wire_adj);
-				wire_adj = 0;
 				if (how & M_NOWAIT) {
 					goto failed;
 				} else {
@@ -1686,15 +1680,12 @@ m_uiotombuf_nomap(struct uio *uio, int how, int len, int maxseg, int flags)
 					goto retry_page;
 				}
 			}
-			wire_adj++;
 			pg_array[i]->flags &= ~PG_ZERO;
 			pgs->pa[i] = VM_PAGE_TO_PHYS(pg_array[i]);
 			pgs->npgs++;
 		}
 		pgs->last_pg_len = length - PAGE_SIZE * (pgs->npgs - 1);
 		MBUF_EXT_PGS_ASSERT_SANITY(pgs);
-		vm_wire_add(wire_adj);
-		wire_adj = 0;
 		total -= length;
 		error = uiomove_fromphys(pg_array, 0, length, uio);
 		if (error != 0)