Module Name: src
Committed By: martin
Date: Tue Aug 1 16:21:07 UTC 2023
Modified Files:
src/lib/libpthread [netbsd-10]: pthread_int.h pthread_spin.c
src/lib/libpthread/arch/aarch64 [netbsd-10]: pthread_md.h
src/lib/libpthread/arch/arm [netbsd-10]: pthread_md.h
src/lib/libpthread/arch/i386 [netbsd-10]: pthread_md.h
src/lib/libpthread/arch/x86_64 [netbsd-10]: pthread_md.h
Log Message:
Pull up following revision(s) (requested by riastradh in ticket #296):
lib/libpthread/arch/x86_64/pthread_md.h: revision 1.13
lib/libpthread/pthread_int.h: revision 1.110
lib/libpthread/pthread_int.h: revision 1.111
lib/libpthread/arch/i386/pthread_md.h: revision 1.21
lib/libpthread/arch/arm/pthread_md.h: revision 1.12
lib/libpthread/arch/arm/pthread_md.h: revision 1.13
lib/libpthread/pthread_spin.c: revision 1.11
lib/libpthread/arch/aarch64/pthread_md.h: revision 1.2
libpthread: Use __nothing, not /* nothing */, for empty macros.
No functional change intended -- just safer to do it this way in case
the macros are used in if branches or comma expressions.
PR port-arm/57437 (pthread__smt_pause/wake issue)
libpthread: New pthread__smt_wait to put CPU in low power for spin.
This is now distinct from pthread__smt_pause, which is for spin lock
backoff with no paired wakeup.
On Arm, there is a single-bit event register per CPU, and there are two
instructions to manage it:
- wfe, wait for event -- if event register is clear, enter low power
mode and wait until event register is set; then exit low power mode
and clear event register
- sev, signal event -- sets event register on all CPUs (other
circumstances like interrupts also set the event register and cause
wfe to wake)
These can be used to reduce the power consumption of spinning for a
lock, but only if they are actually paired -- if there's no sev, wfe
might hang indefinitely. Currently only pthread_spin(3) actually
pairs them; the other lock primitives (internal lock, mutex, rwlock)
do not -- they have spin lock backoff loops, but no corresponding
wakeup to cancel a wfe.
It may be worthwhile to teach the other lock primitives to pair
wfe/sev, but that requires some performance measurement to verify
it's actually worthwhile. So for now, we just make sure not to use
wfe when there's no sev, and keep everything else the same -- this
should fix severe performance degredation in libpthread on Arm
without hurting anything else.
No change in the generated code on amd64 and i386. No change in the
generated code for pthread_spin.c on arm and aarch64 -- changes only
the generated code for pthread_lock.c, pthread_mutex.c, and
pthread_rwlock.c, as intended.
PR port-arm/57437
To generate a diff of this commit:
cvs rdiff -u -r1.109 -r1.109.2.1 src/lib/libpthread/pthread_int.h
cvs rdiff -u -r1.10 -r1.10.2.1 src/lib/libpthread/pthread_spin.c
cvs rdiff -u -r1.1 -r1.1.36.1 src/lib/libpthread/arch/aarch64/pthread_md.h
cvs rdiff -u -r1.11 -r1.11.10.1 src/lib/libpthread/arch/arm/pthread_md.h
cvs rdiff -u -r1.20 -r1.20.42.1 src/lib/libpthread/arch/i386/pthread_md.h
cvs rdiff -u -r1.12 -r1.12.54.1 src/lib/libpthread/arch/x86_64/pthread_md.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/lib/libpthread/pthread_int.h
diff -u src/lib/libpthread/pthread_int.h:1.109 src/lib/libpthread/pthread_int.h:1.109.2.1
--- src/lib/libpthread/pthread_int.h:1.109 Tue Apr 19 20:32:17 2022
+++ src/lib/libpthread/pthread_int.h Tue Aug 1 16:21:07 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: pthread_int.h,v 1.109 2022/04/19 20:32:17 rillig Exp $ */
+/* $NetBSD: pthread_int.h,v 1.109.2.1 2023/08/01 16:21:07 martin Exp $ */
/*-
* Copyright (c) 2001, 2002, 2003, 2006, 2007, 2008, 2020
@@ -301,10 +301,13 @@ int pthread__checkpri(int) PTHREAD_HIDE;
int pthread__add_specific(pthread_t, pthread_key_t, const void *) PTHREAD_HIDE;
#ifndef pthread__smt_pause
-#define pthread__smt_pause() /* nothing */
+#define pthread__smt_pause() __nothing
+#endif
+#ifndef pthread__smt_wait
+#define pthread__smt_wait() __nothing
#endif
#ifndef pthread__smt_wake
-#define pthread__smt_wake() /* nothing */
+#define pthread__smt_wake() __nothing
#endif
/*
Index: src/lib/libpthread/pthread_spin.c
diff -u src/lib/libpthread/pthread_spin.c:1.10 src/lib/libpthread/pthread_spin.c:1.10.2.1
--- src/lib/libpthread/pthread_spin.c:1.10 Sun Apr 10 10:38:33 2022
+++ src/lib/libpthread/pthread_spin.c Tue Aug 1 16:21:07 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: pthread_spin.c,v 1.10 2022/04/10 10:38:33 riastradh Exp $ */
+/* $NetBSD: pthread_spin.c,v 1.10.2.1 2023/08/01 16:21:07 martin Exp $ */
/*-
* Copyright (c) 2001, 2006, 2007 The NetBSD Foundation, Inc.
@@ -34,7 +34,7 @@
*/
#include <sys/cdefs.h>
-__RCSID("$NetBSD: pthread_spin.c,v 1.10 2022/04/10 10:38:33 riastradh Exp $");
+__RCSID("$NetBSD: pthread_spin.c,v 1.10.2.1 2023/08/01 16:21:07 martin Exp $");
/* Need to use libc-private names for atomic operations. */
#include "../../common/lib/libc/atomic/atomic_op_namespace.h"
@@ -98,7 +98,7 @@ pthread_spin_lock(pthread_spinlock_t *lo
self = pthread__self();
while (pthread__spintrylock(self, &lock->pts_spin) == 0) {
- pthread__smt_pause();
+ pthread__smt_wait();
}
return 0;
Index: src/lib/libpthread/arch/aarch64/pthread_md.h
diff -u src/lib/libpthread/arch/aarch64/pthread_md.h:1.1 src/lib/libpthread/arch/aarch64/pthread_md.h:1.1.36.1
--- src/lib/libpthread/arch/aarch64/pthread_md.h:1.1 Sun Aug 10 05:47:37 2014
+++ src/lib/libpthread/arch/aarch64/pthread_md.h Tue Aug 1 16:21:07 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: pthread_md.h,v 1.1 2014/08/10 05:47:37 matt Exp $ */
+/* $NetBSD: pthread_md.h,v 1.1.36.1 2023/08/01 16:21:07 martin Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -42,7 +42,7 @@ pthread__sp(void)
return ret;
}
-#define pthread__smt_pause() __asm __volatile("wfe") /* wfe */
+#define pthread__smt_wait() __asm __volatile("wfe") /* wfe */
#define pthread__smt_wake() __asm __volatile("sev") /* sev */
#define pthread__uc_sp(ucp) ((ucp)->uc_mcontext.__gregs[_REG_SP])
Index: src/lib/libpthread/arch/arm/pthread_md.h
diff -u src/lib/libpthread/arch/arm/pthread_md.h:1.11 src/lib/libpthread/arch/arm/pthread_md.h:1.11.10.1
--- src/lib/libpthread/arch/arm/pthread_md.h:1.11 Thu Nov 22 20:38:59 2018
+++ src/lib/libpthread/arch/arm/pthread_md.h Tue Aug 1 16:21:07 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: pthread_md.h,v 1.11 2018/11/22 20:38:59 skrll Exp $ */
+/* $NetBSD: pthread_md.h,v 1.11.10.1 2023/08/01 16:21:07 martin Exp $ */
/*
* Copyright (c) 2001 Wasabi Systems, Inc.
@@ -50,14 +50,14 @@ pthread__sp(void)
}
#if defined(__thumb__) && defined(_ARM_ARCH_6)
-#define pthread__smt_pause() __asm __volatile(".inst.n 0xbf20") /* wfe */
+#define pthread__smt_wait() __asm __volatile(".inst.n 0xbf20") /* wfe */
#define pthread__smt_wake() __asm __volatile(".inst.n 0xbf40") /* sev */
#elif !defined(__thumb__)
-#define pthread__smt_pause() __asm __volatile(".inst 0xe320f002") /* wfe */
+#define pthread__smt_wait() __asm __volatile(".inst 0xe320f002") /* wfe */
#define pthread__smt_wake() __asm __volatile(".inst 0xe320f004") /* sev */
#else
-#define pthread__smt_pause()
-#define pthread__smt_wake()
+#define pthread__smt_wait() __nothing
+#define pthread__smt_wake() __nothing
#endif
#define pthread__uc_sp(ucp) ((ucp)->uc_mcontext.__gregs[_REG_SP])
Index: src/lib/libpthread/arch/i386/pthread_md.h
diff -u src/lib/libpthread/arch/i386/pthread_md.h:1.20 src/lib/libpthread/arch/i386/pthread_md.h:1.20.42.1
--- src/lib/libpthread/arch/i386/pthread_md.h:1.20 Fri Mar 2 23:19:47 2012
+++ src/lib/libpthread/arch/i386/pthread_md.h Tue Aug 1 16:21:07 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: pthread_md.h,v 1.20 2012/03/02 23:19:47 joerg Exp $ */
+/* $NetBSD: pthread_md.h,v 1.20.42.1 2023/08/01 16:21:07 martin Exp $ */
/*-
* Copyright (c) 2001, 2007, 2008 The NetBSD Foundation, Inc.
@@ -61,6 +61,7 @@ _initcontext_u_md(ucontext_t *ucp)
#define _INITCONTEXT_U_MD(ucp) _initcontext_u_md(ucp);
#define pthread__smt_pause() __asm __volatile("rep; nop" ::: "memory")
+#define pthread__smt_wait() __asm __volatile("rep; nop" ::: "memory")
/* Don't need additional memory barriers. */
#define PTHREAD__ATOMIC_IS_MEMBAR
Index: src/lib/libpthread/arch/x86_64/pthread_md.h
diff -u src/lib/libpthread/arch/x86_64/pthread_md.h:1.12 src/lib/libpthread/arch/x86_64/pthread_md.h:1.12.54.1
--- src/lib/libpthread/arch/x86_64/pthread_md.h:1.12 Tue Jan 25 19:12:06 2011
+++ src/lib/libpthread/arch/x86_64/pthread_md.h Tue Aug 1 16:21:07 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: pthread_md.h,v 1.12 2011/01/25 19:12:06 christos Exp $ */
+/* $NetBSD: pthread_md.h,v 1.12.54.1 2023/08/01 16:21:07 martin Exp $ */
/*-
* Copyright (c) 2001, 2007, 2008 The NetBSD Foundation, Inc.
@@ -64,6 +64,7 @@ pthread__sp(void)
(ucp)->uc_mcontext.__gregs[_REG_RFL] = 0x202;
#define pthread__smt_pause() __asm __volatile("rep; nop" ::: "memory")
+#define pthread__smt_wait() __asm __volatile("rep; nop" ::: "memory")
/* Don't need additional memory barriers. */
#define PTHREAD__ATOMIC_IS_MEMBAR
