From: Alexey Dobriyan <adobriyan@gmail.com>
To: x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/3] x86: support REP MOVSB copy_page()
Date: Tue, 23 Aug 2016 19:25:33 +0300 [thread overview]
Message-ID: <20160823162533.GB2286@p183.telecom.by> (raw)
In-Reply-To: <20160823161920.GA2286@p183.telecom.by>
Microbenchmark shows that "REP MOVSB" copy_page() is faster
than "REP MOVSQ" version on Intel i5-something Haswell
REP_GOOD/ERMS capable CPU.
N=1<<27
rep movsq: 6.758841901 ± 0.04%
rep movsb: 6.253927309 ± 0.02%
-----------------------------------
-7.5%
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
arch/x86/lib/copy_page_64.S | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/arch/x86/lib/copy_page_64.S
+++ b/arch/x86/lib/copy_page_64.S
@@ -12,12 +12,21 @@
*/
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)
+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)
next prev parent reply other threads:[~2016-08-23 16:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-22 20:52 [PATCH] x86: branchless clear_page() Alexey Dobriyan
2016-08-22 20:54 ` Alexey Dobriyan
2016-08-22 21:06 ` Borislav Petkov
2016-08-23 10:46 ` Alexey Dobriyan
2016-08-23 13:43 ` Brian Gerst
2016-08-23 16:15 ` Alexey Dobriyan
2016-08-23 16:19 ` [PATCH 1/3] " Alexey Dobriyan
2016-08-23 16:25 ` Alexey Dobriyan [this message]
2016-08-23 16:28 ` [PATCH 3/3] x86: branchless copy_page() Alexey Dobriyan
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