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From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Sat, 31 Dec 2016 13:23:28 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r310975 - stable/10/sys/amd64/amd64
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Author: mjg
Date: Sat Dec 31 13:23:28 2016
New Revision: 310975
URL: https://svnweb.freebsd.org/changeset/base/310975

Log:
  MFC r303583:
  
      amd64: implement pagezero using rep stos
  
      The current implementation uses non-temporal writes. This turns out to
      be detrimental to performance if the page is used shortly after, which
      is the typical case with page faults.
  
      Switch to rep stos.

Modified:
  stable/10/sys/amd64/amd64/support.S
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/amd64/amd64/support.S
==============================================================================
--- stable/10/sys/amd64/amd64/support.S	Sat Dec 31 13:15:52 2016	(r310974)
+++ stable/10/sys/amd64/amd64/support.S	Sat Dec 31 13:23:28 2016	(r310975)
@@ -65,17 +65,10 @@ END(bzero)
 /* Address: %rdi */
 ENTRY(pagezero)
 	PUSH_FRAME_POINTER
-	movq	$-PAGE_SIZE,%rdx
-	subq	%rdx,%rdi
+	movq	$PAGE_SIZE/8,%rcx
 	xorl	%eax,%eax
-1:
-	movnti	%rax,(%rdi,%rdx)
-	movnti	%rax,8(%rdi,%rdx)
-	movnti	%rax,16(%rdi,%rdx)
-	movnti	%rax,24(%rdi,%rdx)
-	addq	$32,%rdx
-	jne	1b
-	sfence
+	rep
+	stosq
 	POP_FRAME_POINTER
 	ret
 END(pagezero)