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From: Alexey Dobriyan <adobriyan@gmail.com>
To: x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH 1/5] x86_64: use REP MOVSB in copy_page()
Date: Wed, 26 Apr 2017 21:23:19 +0300	[thread overview]
Message-ID: <20170426182318.GA5069@avx2> (raw)

On my Broadwell-era Xeon copying page with REP MOVSB is ~7.8% faster
than with REP MOVSQ. Choose REP MOVSB copy_page() at runtime
with alternatives.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 arch/x86/lib/copy_page_64.S |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/arch/x86/lib/copy_page_64.S
+++ b/arch/x86/lib/copy_page_64.S
@@ -13,13 +13,21 @@
  */
 	ALIGN
 ENTRY(copy_page)
-	ALTERNATIVE "jmp copy_page_regs", "", X86_FEATURE_REP_GOOD
+	ALTERNATIVE_2 "jmp copy_page_regs",	\
+		"", X86_FEATURE_REP_GOOD,	\
+		"jmp copy_page_rep_movsb", X86_FEATURE_ERMS
 	movl	$4096/8, %ecx
 	rep	movsq
 	ret
 ENDPROC(copy_page)
 EXPORT_SYMBOL(copy_page)
 
+ENTRY(copy_page_rep_movsb)
+	mov	$4096, %ecx
+	rep movsb
+	ret
+ENDPROC(copy_page_rep_movsb)
+
 ENTRY(copy_page_regs)
 	subq	$2*8,	%rsp
 	movq	%rbx,	(%rsp)

             reply	other threads:[~2017-04-26 18:24 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-26 18:23 Alexey Dobriyan [this message]
2017-04-26 18:28 ` [PATCH 2/5] x86_64: inline copy_page() at call site Alexey Dobriyan
2017-04-26 18:30   ` [PATCH 3/5] x86_64: rename clear_page() and copy_user() variants Alexey Dobriyan
2017-04-26 18:34     ` [PATCH 4/5] x86_64: clobber "cc" in inlined clear_page() Alexey Dobriyan
2017-04-26 18:35       ` [PATCH 5/5] x86_64: garbage collect headers in clear_page.S Alexey Dobriyan
2017-05-05 16:58     ` [PATCH 3/5] x86_64: rename clear_page() and copy_user() variants Borislav Petkov
2017-04-28 21:04   ` [PATCH 2/5] x86_64: inline copy_page() at call site Borislav Petkov
2017-05-02 11:49     ` Alexey Dobriyan
2017-05-02 11:59       ` Borislav Petkov

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