Module Name: src
Committed By: maxv
Date: Sun Nov 13 12:58:40 UTC 2016
Modified Files:
src/sys/arch/x86/x86: pmap_tlb.c
Log Message:
Explain why this is the right value, otherwise someone (like me) could be
tempted to increase it. The invlpg part is from rmind, the statistical from
me.
To generate a diff of this commit:
cvs rdiff -u -r1.7 -r1.8 src/sys/arch/x86/x86/pmap_tlb.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/x86/x86/pmap_tlb.c
diff -u src/sys/arch/x86/x86/pmap_tlb.c:1.7 src/sys/arch/x86/x86/pmap_tlb.c:1.8
--- src/sys/arch/x86/x86/pmap_tlb.c:1.7 Fri Jul 24 15:20:37 2015
+++ src/sys/arch/x86/x86/pmap_tlb.c Sun Nov 13 12:58:40 2016
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap_tlb.c,v 1.7 2015/07/24 15:20:37 hannken Exp $ */
+/* $NetBSD: pmap_tlb.c,v 1.8 2016/11/13 12:58:40 maxv Exp $ */
/*-
* Copyright (c) 2008-2012 The NetBSD Foundation, Inc.
@@ -40,7 +40,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap_tlb.c,v 1.7 2015/07/24 15:20:37 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap_tlb.c,v 1.8 2016/11/13 12:58:40 maxv Exp $");
#include <sys/param.h>
#include <sys/kernel.h>
@@ -74,7 +74,14 @@ typedef struct {
kcpuset_t * tp_cpumask;
} pmap_tlb_packet_t;
-/* No more than N seperate invlpg. */
+/*
+ * No more than N separate invlpg.
+ *
+ * Statistically, a value of six is big enough to cover the requested number
+ * of pages in ~ 95% of the TLB shootdowns we are getting. We therefore rarely
+ * reach the limit, and increasing it can actually reduce the performance due
+ * to the high cost of invlpg.
+ */
#define TP_MAXVA 6
/*
