All of lore.kernel.org
 help / color / mirror / Atom feed
From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH] powerpc/32: Don't use lmw/stmw for saving/restoring non volatile regs
Date: Mon, 23 Aug 2021 15:29:12 +0000 (UTC)	[thread overview]
Message-ID: <316c543b8906712c108985c8463eec09c8db577b.1629732542.git.christophe.leroy@csgroup.eu> (raw)

Instructions lmw/stmw are interesting for functions that are rarely
used and not in the cache, because only one instruction is to be
copied into the instruction cache instead of 19. However those
instruction are less performant than 19x raw lwz/stw as they require
synchronisation plus one additional cycle.

SAVE_NVGPRS / REST_NVGPRS are used in only a few places which are
mostly in interrupts entries/exits and in task switch so they are
likely already in the cache.

Using standard lwz improves null_syscall selftest by:
- 10 cycles on mpc832x.
- 2 cycles on mpc8xx.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/ppc_asm.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index ffe712307e11..349fc0ec0dbb 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -28,8 +28,8 @@
 #else
 #define SAVE_GPR(n, base)	stw	n,GPR0+4*(n)(base)
 #define REST_GPR(n, base)	lwz	n,GPR0+4*(n)(base)
-#define SAVE_NVGPRS(base)	stmw	13, GPR0+4*13(base)
-#define REST_NVGPRS(base)	lmw	13, GPR0+4*13(base)
+#define SAVE_NVGPRS(base)	SAVE_GPR(13, base); SAVE_8GPRS(14, base); SAVE_10GPRS(22, base)
+#define REST_NVGPRS(base)	REST_GPR(13, base); REST_8GPRS(14, base); REST_10GPRS(22, base)
 #endif
 
 #define SAVE_2GPRS(n, base)	SAVE_GPR(n, base); SAVE_GPR(n+1, base)
-- 
2.25.0


WARNING: multiple messages have this Message-ID (diff)
From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: [PATCH] powerpc/32: Don't use lmw/stmw for saving/restoring non volatile regs
Date: Mon, 23 Aug 2021 15:29:12 +0000 (UTC)	[thread overview]
Message-ID: <316c543b8906712c108985c8463eec09c8db577b.1629732542.git.christophe.leroy@csgroup.eu> (raw)

Instructions lmw/stmw are interesting for functions that are rarely
used and not in the cache, because only one instruction is to be
copied into the instruction cache instead of 19. However those
instruction are less performant than 19x raw lwz/stw as they require
synchronisation plus one additional cycle.

SAVE_NVGPRS / REST_NVGPRS are used in only a few places which are
mostly in interrupts entries/exits and in task switch so they are
likely already in the cache.

Using standard lwz improves null_syscall selftest by:
- 10 cycles on mpc832x.
- 2 cycles on mpc8xx.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/ppc_asm.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index ffe712307e11..349fc0ec0dbb 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -28,8 +28,8 @@
 #else
 #define SAVE_GPR(n, base)	stw	n,GPR0+4*(n)(base)
 #define REST_GPR(n, base)	lwz	n,GPR0+4*(n)(base)
-#define SAVE_NVGPRS(base)	stmw	13, GPR0+4*13(base)
-#define REST_NVGPRS(base)	lmw	13, GPR0+4*13(base)
+#define SAVE_NVGPRS(base)	SAVE_GPR(13, base); SAVE_8GPRS(14, base); SAVE_10GPRS(22, base)
+#define REST_NVGPRS(base)	REST_GPR(13, base); REST_8GPRS(14, base); REST_10GPRS(22, base)
 #endif
 
 #define SAVE_2GPRS(n, base)	SAVE_GPR(n, base); SAVE_GPR(n+1, base)
-- 
2.25.0


             reply	other threads:[~2021-08-23 15:29 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-23 15:29 Christophe Leroy [this message]
2021-08-23 15:29 ` [PATCH] powerpc/32: Don't use lmw/stmw for saving/restoring non volatile regs Christophe Leroy
2021-08-23 18:46 ` Segher Boessenkool
2021-08-23 18:46   ` Segher Boessenkool
2021-08-24  5:54   ` Christophe Leroy
2021-08-24  5:54     ` Christophe Leroy
2021-08-24 13:16     ` Segher Boessenkool
2021-08-24 13:16       ` Segher Boessenkool
2021-08-24 15:28       ` Segher Boessenkool
2021-08-24 15:28         ` Segher Boessenkool
2021-08-25  8:42         ` David Laight
2021-08-25  8:42           ` David Laight
2021-08-25  9:39       ` Christophe Leroy
2021-08-25  9:39         ` Christophe Leroy
2021-11-02 10:11 ` Michael Ellerman
2021-11-02 10:11   ` Michael Ellerman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=316c543b8906712c108985c8463eec09c8db577b.1629732542.git.christophe.leroy@csgroup.eu \
    --to=christophe.leroy@csgroup.eu \
    --cc=benh@kernel.crashing.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mpe@ellerman.id.au \
    --cc=paulus@samba.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.