From 5341c0fbfcdaacfa28fbb256a5141bd2fbd54403 Mon Sep 17 00:00:00 2001 From: Vladimir 'phcoder' Serbinenko Date: Sun, 10 Mar 2013 17:45:38 +0100 Subject: [PATCH] Avoid costly 64-bit division in grub_get_time_ms on most platforms. --- ChangeLog | 4 +++ grub-core/Makefile.am | 14 +++++----- grub-core/Makefile.core.def | 3 --- grub-core/kern/i386/pc/init.c | 6 ++--- grub-core/kern/i386/pit.c | 49 ---------------------------------- grub-core/kern/i386/tsc.c | 50 +++++++++++++++++++++++++++-------- grub-core/loader/i386/xnu.c | 28 +++++++++++--------- include/grub/i386/pc/time.h | 5 ---- include/grub/i386/pit.h | 2 -- include/grub/i386/tsc.h | 2 ++ 10 files changed, 70 insertions(+), 93 deletions(-) delete mode 100644 grub-core/kern/i386/pit.c diff --git a/ChangeLog b/ChangeLog index c604d8d7c..bc51ae9c1 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,7 @@ +2013-03-10 Vladimir Serbinenko + + Avoid costly 64-bit division in grub_get_time_ms on most platforms. + 2013-03-10 Vladimir Serbinenko * grub-core/fs/fshelp.c (grub_fshelp_log2blksize): Remove now unused diff --git a/grub-core/Makefile.am b/grub-core/Makefile.am index 9cb14e27a..221466b36 100644 --- a/grub-core/Makefile.am +++ b/grub-core/Makefile.am @@ -98,29 +98,29 @@ if COND_i386_pc KERNEL_HEADER_FILES += $(top_builddir)/include/grub/machine/kernel.h KERNEL_HEADER_FILES += $(top_builddir)/include/grub/machine/pxe.h KERNEL_HEADER_FILES += $(top_builddir)/include/grub/machine/int.h -KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h +KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h endif if COND_i386_efi KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h -KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h +KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/pci.h endif if COND_i386_coreboot -KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h +KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h KERNEL_HEADER_FILES += $(top_builddir)/include/grub/i386/pc/int.h endif if COND_i386_multiboot -KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h +KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h KERNEL_HEADER_FILES += $(top_builddir)/include/grub/i386/pc/int.h endif if COND_i386_qemu KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/pci.h -KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h +KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h endif if COND_i386_ieee1275 @@ -128,13 +128,13 @@ KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/ieee1275/ieee1275.h KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/terminfo.h KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/extcmd.h KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/lib/arg.h -KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h +KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h endif if COND_x86_64_efi KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h -KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h +KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/pci.h endif diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def index 93ff2a8a3..3bcf66232 100644 --- a/grub-core/Makefile.core.def +++ b/grub-core/Makefile.core.def @@ -102,7 +102,6 @@ kernel = { noemu_nodist = symlist.c; - i386_pc = kern/generic/rtc_get_time_ms.c; mips = kern/generic/rtc_get_time_ms.c; ieee1275 = disk/ieee1275/ofdisk.c; @@ -123,8 +122,6 @@ kernel = { i386_coreboot_multiboot_qemu = kern/i386/coreboot/init.c; i386_coreboot_multiboot_qemu = term/i386/pc/vga_text.c; - x86 = kern/i386/pit.c; - efi = disk/efi/efidisk.c; efi = kern/efi/efi.c; efi = kern/efi/init.c; diff --git a/grub-core/kern/i386/pc/init.c b/grub-core/kern/i386/pc/init.c index 730e04ac4..5b685040a 100644 --- a/grub-core/kern/i386/pc/init.c +++ b/grub-core/kern/i386/pc/init.c @@ -52,8 +52,8 @@ void (*grub_pc_net_config) (char **device, char **path); * return the real time in ticks, of which there are about * 18-20 per second */ -grub_uint32_t -grub_get_rtc (void) +grub_uint64_t +grub_rtc_get_time_ms (void) { struct grub_bios_int_registers regs; @@ -61,7 +61,7 @@ grub_get_rtc (void) regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT; grub_bios_interrupt (0x1a, ®s); - return (regs.ecx << 16) | (regs.edx & 0xffff); + return ((regs.ecx << 16) | (regs.edx & 0xffff)) * 55ULL; } void diff --git a/grub-core/kern/i386/pit.c b/grub-core/kern/i386/pit.c deleted file mode 100644 index 092481ae5..000000000 --- a/grub-core/kern/i386/pit.c +++ /dev/null @@ -1,49 +0,0 @@ -/* - * GRUB -- GRand Unified Bootloader - * Copyright (C) 2008 Free Software Foundation, Inc. - * - * GRUB is free software: you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation, either version 3 of the License, or - * (at your option) any later version. - * - * GRUB is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with GRUB. If not, see . - */ - -#include -#include -#include - -void -grub_pit_wait (grub_uint16_t tics) -{ - /* Disable timer2 gate and speaker. */ - grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT) - & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2), - GRUB_PIT_SPEAKER_PORT); - - /* Set tics. */ - grub_outb (GRUB_PIT_CTRL_SELECT_2 | GRUB_PIT_CTRL_READLOAD_WORD, - GRUB_PIT_CTRL); - grub_outb (tics & 0xff, GRUB_PIT_COUNTER_2); - grub_outb (tics >> 8, GRUB_PIT_COUNTER_2); - - /* Enable timer2 gate, keep speaker disabled. */ - grub_outb ((grub_inb (GRUB_PIT_SPEAKER_PORT) & ~ GRUB_PIT_SPK_DATA) - | GRUB_PIT_SPK_TMR2, - GRUB_PIT_SPEAKER_PORT); - - /* Wait. */ - while ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH) == 0x00); - - /* Disable timer2 gate and speaker. */ - grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT) - & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2), - GRUB_PIT_SPEAKER_PORT); -} diff --git a/grub-core/kern/i386/tsc.c b/grub-core/kern/i386/tsc.c index c4645f043..9efd6338c 100644 --- a/grub-core/kern/i386/tsc.c +++ b/grub-core/kern/i386/tsc.c @@ -25,37 +25,66 @@ #include #include #include +#include /* This defines the value TSC had at the epoch (that is, when we calibrated it). */ static grub_uint64_t tsc_boot_time; -/* Calibrated TSC rate. (In TSC ticks per millisecond.) */ -static grub_uint64_t tsc_ticks_per_ms; +/* Calibrated TSC rate. (In ms per 2^32 ticks) */ +/* We assume that the tick is less than 1 ms and hence this value fits + in 32-bit. */ +grub_uint32_t grub_tsc_rate; +static void +grub_pit_wait (grub_uint16_t tics) +{ + /* Disable timer2 gate and speaker. */ + grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT) + & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2), + GRUB_PIT_SPEAKER_PORT); + + /* Set tics. */ + grub_outb (GRUB_PIT_CTRL_SELECT_2 | GRUB_PIT_CTRL_READLOAD_WORD, + GRUB_PIT_CTRL); + grub_outb (tics & 0xff, GRUB_PIT_COUNTER_2); + grub_outb (tics >> 8, GRUB_PIT_COUNTER_2); + + /* Enable timer2 gate, keep speaker disabled. */ + grub_outb ((grub_inb (GRUB_PIT_SPEAKER_PORT) & ~ GRUB_PIT_SPK_DATA) + | GRUB_PIT_SPK_TMR2, + GRUB_PIT_SPEAKER_PORT); + + /* Wait. */ + while ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH) == 0x00); + + /* Disable timer2 gate and speaker. */ + grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT) + & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2), + GRUB_PIT_SPEAKER_PORT); +} grub_uint64_t grub_tsc_get_time_ms (void) { - return tsc_boot_time + grub_divmod64 (grub_get_tsc (), tsc_ticks_per_ms, 0); + grub_uint64_t a = grub_get_tsc () - tsc_boot_time; + grub_uint64_t ah = a >> 32; + grub_uint64_t al = a & 0xffffffff; + + return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate; } - -/* How many RTC ticks to use for calibration loop. (>= 1) */ -#define CALIBRATION_TICKS 2 - /* Calibrate the TSC based on the RTC. */ static void calibrate_tsc (void) { /* First calibrate the TSC rate (relative, not absolute time). */ - grub_uint64_t start_tsc; grub_uint64_t end_tsc; - start_tsc = grub_get_tsc (); + tsc_boot_time = grub_get_tsc (); grub_pit_wait (0xffff); end_tsc = grub_get_tsc (); - tsc_ticks_per_ms = grub_divmod64 (end_tsc - start_tsc, 55, 0); + grub_tsc_rate = grub_divmod64 ((55ULL << 32), end_tsc - tsc_boot_time, 0); } void @@ -63,7 +92,6 @@ grub_tsc_init (void) { if (grub_cpu_is_tsc_supported ()) { - tsc_boot_time = grub_get_tsc (); calibrate_tsc (); grub_install_get_time_ms (grub_tsc_get_time_ms); } diff --git a/grub-core/loader/i386/xnu.c b/grub-core/loader/i386/xnu.c index 4e5ce0975..497529bc3 100644 --- a/grub-core/loader/i386/xnu.c +++ b/grub-core/loader/i386/xnu.c @@ -125,9 +125,6 @@ guessfsb (void) { const grub_uint64_t sane_value = 100000000; grub_uint32_t manufacturer[3], max_cpuid, capabilities, msrlow; - grub_uint64_t start_tsc; - grub_uint64_t end_tsc; - grub_uint64_t tsc_ticks_per_ms; if (! grub_cpu_is_cpuid_supported ()) return sane_value; @@ -192,14 +189,6 @@ guessfsb (void) if (! (capabilities & (1 << 7))) return sane_value; - /* Calibrate the TSC rate. */ - - start_tsc = grub_get_tsc (); - grub_pit_wait (0xffff); - end_tsc = grub_get_tsc (); - - tsc_ticks_per_ms = grub_divmod64 (end_tsc - start_tsc, 55, 0); - /* Read the multiplier. */ asm volatile ("movl $0x198, %%ecx\n" "rdmsr" @@ -207,8 +196,21 @@ guessfsb (void) : : "%ecx", "%eax"); - return grub_divmod64 (2000 * tsc_ticks_per_ms, - ((msrlow >> 7) & 0x3e) + ((msrlow >> 14) & 1), 0); + grub_uint64_t v; + grub_uint32_t r; + + /* (2000ULL << 32) / grub_tsc_rate */ + /* Assumption: TSC frequency is over 2 MHz. */ + v = 0xffffffff / grub_tsc_rate; + v *= 2000; + /* v is at most 2000 off from (2000ULL << 32) / grub_tsc_rate. + Since grub_tsc_rate < 2^32/2^11=2^21, so no overflow. + */ + r = (2000ULL << 32) - v * grub_tsc_rate; + v += r / grub_tsc_rate; + + return grub_divmod64 (v, ((msrlow >> 7) & 0x3e) | ((msrlow >> 14) & 1), + 0); } struct property_descriptor diff --git a/include/grub/i386/pc/time.h b/include/grub/i386/pc/time.h index ba227ca6f..e93320f71 100644 --- a/include/grub/i386/pc/time.h +++ b/include/grub/i386/pc/time.h @@ -21,9 +21,4 @@ #include -#define GRUB_TICKS_PER_SECOND 18 - -/* Return the real time in ticks. */ -grub_uint32_t grub_get_rtc (void); - #endif /* ! KERNEL_MACHINE_TIME_HEADER */ diff --git a/include/grub/i386/pit.h b/include/grub/i386/pit.h index e1c92cd16..4bd49d4ca 100644 --- a/include/grub/i386/pit.h +++ b/include/grub/i386/pit.h @@ -100,6 +100,4 @@ enum GRUB_PIT_CTRL_COUNT_BCD = 0x01 /* 4-decade BCD counter. */ }; -void EXPORT_FUNC(grub_pit_wait) (grub_uint16_t tics); - #endif /* ! KERNEL_CPU_PIT_HEADER */ diff --git a/include/grub/i386/tsc.h b/include/grub/i386/tsc.h index 2442d7e24..d25d0e3e9 100644 --- a/include/grub/i386/tsc.h +++ b/include/grub/i386/tsc.h @@ -137,5 +137,7 @@ grub_cpu_is_tsc_supported (void) void grub_tsc_init (void); grub_uint64_t grub_tsc_get_time_ms (void); +/* In ms per 2^32 ticks. */ +extern grub_uint32_t EXPORT_VAR(grub_tsc_rate); #endif /* ! KERNEL_CPU_TSC_HEADER */