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From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	nathanl@linux.ibm.com, arnd@arndb.de, tglx@linutronix.de,
	vincenzo.frascino@arm.com, luto@kernel.org
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,
	x86@kernel.org
Subject: [RFC PATCH v4 06/11] powerpc/vdso: provide inline alternative to __get_datapage()
Date: Thu, 16 Jan 2020 17:58:30 +0000 (UTC)
Message-ID: <2e730f4e6ef77be2d5bfc38273d8a622e2cb4f97.1579196675.git.christophe.leroy@c-s.fr> (raw)
In-Reply-To: <cover.1579196675.git.christophe.leroy@c-s.fr>

__get_datapage() is only a few instructions to retrieve the
address of the page where the kernel stores data to the VDSO.

By inlining this function into its users, a bl/blr pair and
a mflr/mtlr pair is avoided, plus a few reg moves.

The improvement is noticeable (about 55 nsec/call on an 8xx)

With current __get_datapage() function:
gettimeofday:    vdso: 731 nsec/call
clock-gettime-realtime-coarse:    vdso: 668 nsec/call
clock-gettime-monotonic-coarse:    vdso: 745 nsec/call

Using the __get_datapage macro provided by this patch:
gettimeofday:    vdso: 677 nsec/call
clock-gettime-realtime-coarse:    vdso: 613 nsec/call
clock-gettime-monotonic-coarse:    vdso: 690 nsec/call

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/include/asm/vdso_datapage.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
index 4d7965bf369e..7342cc0c1ae4 100644
--- a/arch/powerpc/include/asm/vdso_datapage.h
+++ b/arch/powerpc/include/asm/vdso_datapage.h
@@ -105,6 +105,17 @@ struct vdso_arch_data {
 
 extern struct vdso_arch_data *vdso_data;
 
+#else /* __ASSEMBLY__ */
+
+.macro get_datapage ptr, offset=0
+	bcl	20, 31, .+4
+	mflr	\ptr
+#if CONFIG_PPC_PAGE_SHIFT > 14
+	addis	\ptr, \ptr, (_vdso_datapage + \offset - (.-4))@ha
+#endif
+	addi	\ptr, \ptr, (_vdso_datapage + \offset - (.-4))@l
+.endm
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __KERNEL__ */
-- 
2.13.3


  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16 17:58 [RFC PATCH v4 00/11] powerpc: switch VDSO to C implementation Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 01/11] powerpc/64: Don't provide time functions in compat VDSO32 Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 02/11] powerpc/vdso: Switch VDSO to generic C implementation Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 03/11] lib: vdso: only read hrtimer_res when needed in __cvdso_clock_getres() Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 04/11] powerpc/vdso: simplify __get_datapage() Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 05/11] lib: vdso: allow arches to provide vdso data pointer Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy [this message]
2020-01-16 17:58 ` [RFC PATCH v4 07/11] powerpc/vdso: provide vdso data pointer from the ASM caller Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 08/11] lib: vdso: allow fixed clock mode Christophe Leroy
2020-01-16 20:13   ` Thomas Gleixner
2020-01-16 20:19     ` Andy Lutomirski
2020-01-16 21:07       ` Thomas Gleixner
2020-01-16 17:58 ` [RFC PATCH v4 09/11] powerpc/vdso: override __arch_vdso_capable() Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 10/11] lib: vdso: Allow arches to override the ns shift operation Christophe Leroy
2020-01-16 19:47   ` Andy Lutomirski
2020-01-16 19:57     ` Thomas Gleixner
2020-01-16 20:20       ` Andy Lutomirski
2020-01-29  7:14         ` Thomas Gleixner
2020-01-29  7:26           ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 11/11] powerpc/32: provide vdso_shift_ns() Christophe Leroy
2020-01-17  8:58 ` [RFC PATCH v4 00/11] powerpc: switch VDSO to C implementation Segher Boessenkool
2020-01-17  9:26   ` Christophe Leroy
2020-01-20 14:56   ` Christophe Leroy
2020-01-20 15:19     ` Segher Boessenkool
2020-01-20 17:08       ` Christophe Leroy
2020-01-20 17:27         ` Segher Boessenkool

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