From d47c03e078f39034d1843dfe8a84aedff40638ba Mon Sep 17 00:00:00 2001
From: Vladimir 'phcoder' Serbinenko <phcoder@gmail.com>
Date: Sun, 10 Mar 2013 17:45:38 +0100
Subject: [PATCH 200/364] 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 c604d8d..bc51ae9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
2013-03-10 Vladimir Serbinenko <phcoder@gmail.com>
+ Avoid costly 64-bit division in grub_get_time_ms on most platforms.
+
+2013-03-10 Vladimir Serbinenko <phcoder@gmail.com>
+
* grub-core/fs/fshelp.c (grub_fshelp_log2blksize): Remove now unused
function.
diff --git a/grub-core/Makefile.am b/grub-core/Makefile.am
index 9cb14e2..221466b 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 93ff2a8..3bcf662 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 730e04a..5b68504 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 092481a..0000000
--- 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 <http://www.gnu.org/licenses/>.
- */
-
-#include <grub/types.h>
-#include <grub/i386/io.h>
-#include <grub/i386/pit.h>
-
-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 c4645f0..9efd633 100644
--- a/grub-core/kern/i386/tsc.c
+++ b/grub-core/kern/i386/tsc.c
@@ -25,37 +25,66 @@
#include <grub/misc.h>
#include <grub/i386/tsc.h>
#include <grub/i386/pit.h>
+#include <grub/cpu/io.h>
/* 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;
-
-/* How many RTC ticks to use for calibration loop. (>= 1) */
-#define CALIBRATION_TICKS 2
+ return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate;
+}
/* 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 4e5ce09..497529b 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 ba227ca..e93320f 100644
--- a/include/grub/i386/pc/time.h
+++ b/include/grub/i386/pc/time.h
@@ -21,9 +21,4 @@
#include <grub/symbol.h>
-#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 e1c92cd..4bd49d4 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 2442d7e..d25d0e3 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 */
--
1.8.1.4