1680854946
Right now, userspace (fast) gettimeofday(2) on x86 only works for
RDTSC. For older machines, like Core2, where RDTSC is not C2/C3
invariant, and which fall to HPET hardware, this means that the call
has both the penalty of the syscall and of the uncached hw behind the
QPI or PCIe connection to the sought bridge. Nothing can me done
against the access latency, but the syscall overhead can be removed.
System already provides mappable /dev/hpetX devices, which gives
straight access to the HPET registers page.
Add yet another algorithm to the x86 'vdso' timehands. Libc is updated
to handle both RDTSC and HPET. For HPET, the index of the hpet device
to mmap is passed from kernel to userspace, index might be changed and
libc invalidates its mapping as needed.
Remove cpu_fill_vdso_timehands() KPI, instead require that
timecounters which can be used from userspace, to provide
tc_fill_vdso_timehands{,32}() methods. Merge i386 and amd64
libc/<arch>/sys/__vdso_gettc.c into one source file in the new
libc/x86/sys location. __vdso_gettc() internal interface is changed
to move timecounter algorithm detection into the MD code.
Measurements show that RDTSC even with the syscall overhead is faster
than userspace HPET access. But still, userspace HPET is three-four
times faster than syscall HPET on several Core2 and SandyBridge
machines.
Tested by: Howard Su <howard0su@gmail.com>
Sponsored by: The FreeBSD Foundation
MFC after: 1 month
Differential revision: https://reviews.freebsd.org/D7473
79 lines
3.2 KiB
C
79 lines
3.2 KiB
C
/*-
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* Copyright (c) 2005 Poul-Henning Kamp
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef __ACPI_HPET_H__
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#define __ACPI_HPET_H__
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#define HPET_MEM_WIDTH 0x400 /* Expected memory region size */
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/* General registers */
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#define HPET_CAPABILITIES 0x0 /* General capabilities and ID */
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#define HPET_CAP_VENDOR_ID 0xffff0000
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#define HPET_CAP_LEG_RT 0x00008000
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#define HPET_CAP_COUNT_SIZE 0x00002000 /* 1 = 64-bit, 0 = 32-bit */
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#define HPET_CAP_NUM_TIM 0x00001f00
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#define HPET_CAP_REV_ID 0x000000ff
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#define HPET_PERIOD 0x4 /* Period (1/hz) of timer */
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#define HPET_CONFIG 0x10 /* General configuration register */
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#define HPET_CNF_LEG_RT 0x00000002
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#define HPET_CNF_ENABLE 0x00000001
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#define HPET_ISR 0x20 /* General interrupt status register */
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#define HPET_MAIN_COUNTER 0xf0 /* Main counter register */
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/* Timer registers */
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#define HPET_TIMER_CAP_CNF(x) ((x) * 0x20 + 0x100)
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#define HPET_TCAP_INT_ROUTE 0xffffffff00000000
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#define HPET_TCAP_FSB_INT_DEL 0x00008000
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#define HPET_TCNF_FSB_EN 0x00004000
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#define HPET_TCNF_INT_ROUTE 0x00003e00
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#define HPET_TCNF_32MODE 0x00000100
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#define HPET_TCNF_VAL_SET 0x00000040
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#define HPET_TCAP_SIZE 0x00000020 /* 1 = 64-bit, 0 = 32-bit */
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#define HPET_TCAP_PER_INT 0x00000010 /* Supports periodic interrupts */
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#define HPET_TCNF_TYPE 0x00000008 /* 1 = periodic, 0 = one-shot */
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#define HPET_TCNF_INT_ENB 0x00000004
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#define HPET_TCNF_INT_TYPE 0x00000002 /* 1 = level triggered, 0 = edge */
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#define HPET_TIMER_COMPARATOR(x) ((x) * 0x20 + 0x108)
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#define HPET_TIMER_FSB_VAL(x) ((x) * 0x20 + 0x110)
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#define HPET_TIMER_FSB_ADDR(x) ((x) * 0x20 + 0x114)
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#define HPET_MIN_CYCLES 128 /* Period considered reliable. */
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#ifdef _KERNEL
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struct timecounter;
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struct vdso_timehands;
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struct vdso_timehands32;
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uint32_t hpet_vdso_timehands(struct vdso_timehands *vdso_th,
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struct timecounter *tc);
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uint32_t hpet_vdso_timehands32(struct vdso_timehands32 *vdso_th32,
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struct timecounter *tc);
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#endif
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#endif /* !__ACPI_HPET_H__ */
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