Use struct vdso_timehands data to implement fast gettimeofday(2) and

clock_gettime(2) functions if supported. The speedup seen in
microbenchmarks is in range 4x-7x depending on the hardware.

Only amd64 and i386 architectures are supported. Libc uses rdtsc and
kernel data to calculate current time, if enabled by kernel.

Hopefully, this code is going to migrate into vdso in some future.

Discussed with:	bde
Reviewed by:	jhb
Tested by:	flo
MFC after:	1 month

10 files changed, 374 insertions, 2 deletions

diff --git a/lib/libc/amd64/sys/Makefile.inc b/lib/libc/amd64/sys/Makefile.inc
index c7b17e0..51583d3 100644
--- a/lib/libc/amd64/sys/Makefile.inc
+++ b/lib/libc/amd64/sys/Makefile.inc
@@ -1,7 +1,8 @@
 #	from: Makefile.inc,v 1.1 1993/09/03 19:04:23 jtc Exp
 # $FreeBSD$
 
-SRCS+=	amd64_get_fsbase.c amd64_get_gsbase.c amd64_set_fsbase.c amd64_set_gsbase.c
+SRCS+=	amd64_get_fsbase.c amd64_get_gsbase.c amd64_set_fsbase.c \
+	amd64_set_gsbase.c __vdso_gettc.c
 
 MDASM=	vfork.S brk.S cerror.S exect.S getcontext.S pipe.S ptrace.S \
 	reboot.S sbrk.S setlogin.S sigreturn.S
diff --git a/lib/libc/amd64/sys/__vdso_gettc.c b/lib/libc/amd64/sys/__vdso_gettc.c
new file mode 100644
index 0000000..091fe26
--- /dev/null
+++ b/lib/libc/amd64/sys/__vdso_gettc.c
@@ -0,0 +1,49 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/vdso.h>
+#include <machine/cpufunc.h>
+
+static u_int
+__vdso_gettc_low(const struct vdso_timehands *th)
+{
+	uint32_t rv;
+
+	__asm __volatile("rdtsc; shrd %%cl, %%edx, %0"
+	    : "=a" (rv) : "c" (th->th_x86_shift) : "edx");
+	return (rv);
+}
+
+u_int
+__vdso_gettc(const struct vdso_timehands *th)
+{
+
+	return (th->th_x86_shift > 0 ? __vdso_gettc_low(th) : rdtsc32());
+}
diff --git a/lib/libc/gen/aux.c b/lib/libc/gen/aux.c
index 4bf8643..3767ac0 100644
--- a/lib/libc/gen/aux.c
+++ b/lib/libc/gen/aux.c
@@ -66,6 +66,7 @@ __init_elf_aux_vector(void)
 static pthread_once_t aux_once = PTHREAD_ONCE_INIT;
 static int pagesize, osreldate, canary_len, ncpus, pagesizes_len;
 static char *canary, *pagesizes;
+static void *timekeep;
 
 static void
 init_aux(void)
@@ -101,6 +102,10 @@ init_aux(void)
 		case AT_NCPUS:
 			ncpus = aux->a_un.a_val;
 			break;
+
+		case AT_TIMEKEEP:
+			timekeep = aux->a_un.a_ptr;
+			break;
 		}
 	}
 }
@@ -163,6 +168,16 @@ _elf_aux_info(int aux, void *buf, int buflen)
 		} else
 			res = EINVAL;
 		break;
+	case AT_TIMEKEEP:
+		if (buflen == sizeof(void *)) {
+			if (timekeep != NULL) {
+				*(void **)buf = timekeep;
+				res = 0;
+			} else
+				res = ENOENT;
+		} else
+			res = EINVAL;
+		break;
 	default:
 		res = ENOENT;
 		break;
diff --git a/lib/libc/i386/sys/Makefile.inc b/lib/libc/i386/sys/Makefile.inc
index 98a9c9e..9eefabc 100644
--- a/lib/libc/i386/sys/Makefile.inc
+++ b/lib/libc/i386/sys/Makefile.inc
@@ -5,7 +5,8 @@
 SRCS+=	i386_clr_watch.c i386_set_watch.c i386_vm86.c
 .endif
 SRCS+=	i386_get_fsbase.c i386_get_gsbase.c i386_get_ioperm.c i386_get_ldt.c \
-	i386_set_fsbase.c i386_set_gsbase.c i386_set_ioperm.c i386_set_ldt.c
+	i386_set_fsbase.c i386_set_gsbase.c i386_set_ioperm.c i386_set_ldt.c \
+	__vdso_gettc.c
 
 MDASM=	Ovfork.S brk.S cerror.S exect.S getcontext.S pipe.S ptrace.S \
 	reboot.S sbrk.S setlogin.S sigreturn.S syscall.S
diff --git a/lib/libc/i386/sys/__vdso_gettc.c b/lib/libc/i386/sys/__vdso_gettc.c
new file mode 100644
index 0000000..4419141
--- /dev/null
+++ b/lib/libc/i386/sys/__vdso_gettc.c
@@ -0,0 +1,50 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/vdso.h>
+#include <machine/cpufunc.h>
+
+static u_int
+__vdso_gettc_low(const struct vdso_timehands *th)
+{
+	uint32_t rv;
+
+	__asm __volatile("rdtsc; shrd %%cl, %%edx, %0"
+	    : "=a" (rv) : "c" (th->th_x86_shift) : "edx");
+	return (rv);
+}
+
+#pragma weak __vdso_gettc
+u_int
+__vdso_gettc(const struct vdso_timehands *th)
+{
+
+	return (th->th_x86_shift > 0 ? __vdso_gettc_low(th) : rdtsc32());
+}
diff --git a/lib/libc/include/libc_private.h b/lib/libc/include/libc_private.h
index 2182f46..faae028 100644
--- a/lib/libc/include/libc_private.h
+++ b/lib/libc/include/libc_private.h
@@ -34,6 +34,7 @@
 
 #ifndef _LIBC_PRIVATE_H_
 #define _LIBC_PRIVATE_H_
+#include <sys/_types.h>
 #include <sys/_pthreadtypes.h>
 
 /*
@@ -245,6 +246,12 @@ extern void *	__sys_freebsd6_mmap(void *, __size_t, int, int, int, int, __off_t)
 /* Without back-compat translation */
 extern int	__sys_fcntl(int, int, ...);
 
+struct timespec;
+struct timeval;
+struct timezone;
+int	__sys_gettimeofday(struct timeval *, struct timezone *);
+int	__sys_clock_gettime(__clockid_t, struct timespec *ts);
+
 /* execve() with PATH processing to implement posix_spawnp() */
 int _execvpe(const char *, char * const *, char * const *);
 
diff --git a/lib/libc/sys/Makefile.inc b/lib/libc/sys/Makefile.inc
index 61d1713..df4ef42 100644
--- a/lib/libc/sys/Makefile.inc
+++ b/lib/libc/sys/Makefile.inc
@@ -15,6 +15,10 @@
 #
 .sinclude "${.CURDIR}/${LIBC_ARCH}/sys/Makefile.inc"
 
+SRCS+= clock_gettime.c gettimeofday.c __vdso_gettimeofday.c
+NOASM+=  clock_gettime.o gettimeofday.o
+PSEUDO+= _clock_gettime.o _gettimeofday.o
+
 # Sources common to both syscall interfaces:
 SRCS+=	stack_protector.c stack_protector_compat.c __error.c
 .if !defined(WITHOUT_SYSCALL_COMPAT)
diff --git a/lib/libc/sys/__vdso_gettimeofday.c b/lib/libc/sys/__vdso_gettimeofday.c
new file mode 100644
index 0000000..32abb69
--- /dev/null
+++ b/lib/libc/sys/__vdso_gettimeofday.c
@@ -0,0 +1,142 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/elf.h>
+#include <sys/time.h>
+#include <sys/vdso.h>
+#include <errno.h>
+#include <time.h>
+#include <machine/atomic.h>
+#include "libc_private.h"
+
+static u_int
+tc_delta(const struct vdso_timehands *th)
+{
+
+	return ((__vdso_gettc(th) - th->th_offset_count) &
+	    th->th_counter_mask);
+}
+
+static int
+binuptime(struct bintime *bt, struct vdso_timekeep *tk, int abs)
+{
+	struct vdso_timehands *th;
+	uint32_t curr, gen;
+
+	do {
+		if (!tk->tk_enabled)
+			return (ENOSYS);
+
+		/*
+		 * XXXKIB. The load of tk->tk_current should use
+		 * atomic_load_acq_32 to provide load barrier. But
+		 * since tk points to r/o mapped page, x86
+		 * implementation of atomic_load_acq faults.
+		 */
+		curr = tk->tk_current;
+		rmb();
+		th = &tk->tk_th[curr];
+		if (th->th_algo != VDSO_TH_ALGO_1)
+			return (ENOSYS);
+		gen = th->th_gen;
+		*bt = th->th_offset;
+		bintime_addx(bt, th->th_scale * tc_delta(th));
+		if (abs)
+			bintime_add(bt, &th->th_boottime);
+
+		/*
+		 * Barrier for load of both tk->tk_current and th->th_gen.
+		 */
+		rmb();
+	} while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
+	return (0);
+}
+
+static struct vdso_timekeep *tk;
+
+int
+__vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+	struct bintime bt;
+	int error;
+
+	if (tz != NULL)
+		return (ENOSYS);
+	if (tk == NULL) {
+		error = _elf_aux_info(AT_TIMEKEEP, &tk, sizeof(tk));
+		if (error != 0 || tk == NULL)
+			return (ENOSYS);
+	}
+	if (tk->tk_ver != VDSO_TK_VER_CURR)
+		return (ENOSYS);
+	error = binuptime(&bt, tk, 1);
+	if (error != 0)
+		return (error);
+	bintime2timeval(&bt, tv);
+	return (0);
+}
+
+int
+__vdso_clock_gettime(clockid_t clock_id, struct timespec *ts)
+{
+	struct bintime bt;
+	int abs, error;
+
+	if (tk == NULL) {
+		error = _elf_aux_info(AT_TIMEKEEP, &tk, sizeof(tk));
+		if (error != 0 || tk == NULL)
+			return (ENOSYS);
+	}
+	if (tk->tk_ver != VDSO_TK_VER_CURR)
+		return (ENOSYS);
+	switch (clock_id) {
+	case CLOCK_REALTIME:
+	case CLOCK_REALTIME_PRECISE:
+	case CLOCK_REALTIME_FAST:
+	case CLOCK_SECOND:
+		abs = 1;
+		break;
+	case CLOCK_MONOTONIC:
+	case CLOCK_MONOTONIC_PRECISE:
+	case CLOCK_MONOTONIC_FAST:
+	case CLOCK_UPTIME:
+	case CLOCK_UPTIME_PRECISE:
+	case CLOCK_UPTIME_FAST:
+		abs = 0;
+		break;
+	default:
+		return (ENOSYS);
+	}
+	error = binuptime(&bt, tk, abs);
+	if (error != 0)
+		return (error);
+	bintime2timespec(&bt, ts);
+	if (clock_id == CLOCK_SECOND)
+		ts->tv_nsec = 0;
+	return (0);
+}
diff --git a/lib/libc/sys/clock_gettime.c b/lib/libc/sys/clock_gettime.c
new file mode 100644
index 0000000..e7e701b
--- /dev/null
+++ b/lib/libc/sys/clock_gettime.c
@@ -0,0 +1,52 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <sys/vdso.h>
+#include <errno.h>
+#include <time.h>
+#include "libc_private.h"
+
+int __clock_gettime(clockid_t, struct timespec *ts);
+
+__weak_reference(__clock_gettime, clock_gettime);
+
+int
+__clock_gettime(clockid_t clock_id, struct timespec *ts)
+{
+	int error;
+
+	if (__vdso_clock_gettime != NULL && __vdso_gettc != NULL)
+		error = __vdso_clock_gettime(clock_id, ts);
+	else
+		error = ENOSYS;
+	if (error == ENOSYS)
+		error = __sys_clock_gettime(clock_id, ts);
+	return (error);
+}
diff --git a/lib/libc/sys/gettimeofday.c b/lib/libc/sys/gettimeofday.c
new file mode 100644
index 0000000..4cc87e1
--- /dev/null
+++ b/lib/libc/sys/gettimeofday.c
@@ -0,0 +1,51 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <sys/vdso.h>
+#include <errno.h>
+#include "libc_private.h"
+
+int __gettimeofday(struct timeval *tv, struct timezone *tz);
+
+__weak_reference(__gettimeofday, gettimeofday);
+
+int
+__gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+	int error;
+
+	if (__vdso_gettimeofday != NULL && __vdso_gettc != NULL)
+		error = __vdso_gettimeofday(tv, tz);
+	else
+		error = ENOSYS;
+	if (error == ENOSYS)
+		error = __sys_gettimeofday(tv, tz);
+	return (error);
+}