ab23c2784b
Stop attempting to use FADT legacy hardware flag, it is almost always a lie. Instead, unless user explicitly disabled the calibration, calibrate against 8254 ISA clock. Then, obtain the rough value of the expected TSC frequency from CPUID leafs 0x15/0x16 or even from the CPU marketing name string. If calibration results look unbelievably bogus comparing with CPUID leafs report, use CPUID one. Intel does not recommend to use CPUID leaf 0x16 for the value of the system time frequency, indeed the error there might be up to 1% which e.g. makes ntpd give up. If ISA clock is present, we win, if not, we get some frequency that allows the machine to boot without enormous delay. Next improvement would be to use HPET for re-calibration if we decided that ISA clock gives bogus results, after HPETs are enumerated. This is a much bigger change since we probably would need to re-evaluate some constants depending on TSC frequency. Reviewed by: emaste, jhb, scottl Tested by: scottl Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D24426
FreeBSD Source:
This is the top level of the FreeBSD source directory. This file
was last revised on:
FreeBSD
FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms. A large community has continually developed it for more than thirty years. Its advanced networking, security, and storage features have made FreeBSD the platform of choice for many of the busiest web sites and most pervasive embedded networking and storage devices.
For copyright information, please see the file COPYRIGHT in this directory. Additional copyright information also exists for some sources in this tree - please see the specific source directories for more information.
The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree. See build(7), config(8), https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html, and https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html for more information, including setting make(1) variables.
Source Roadmap:
bin System/user commands.
cddl Various commands and libraries under the Common Development
and Distribution License.
contrib Packages contributed by 3rd parties.
crypto Cryptography stuff (see crypto/README).
etc Template files for /etc.
gnu Various commands and libraries under the GNU Public License.
Please see gnu/COPYING* for more information.
include System include files.
kerberos5 Kerberos5 (Heimdal) package.
lib System libraries.
libexec System daemons.
release Release building Makefile & associated tools.
rescue Build system for statically linked /rescue utilities.
sbin System commands.
secure Cryptographic libraries and commands.
share Shared resources.
stand Boot loader sources.
sys Kernel sources.
sys/<arch>/conf Kernel configuration files. GENERIC is the configuration
used in release builds. NOTES contains documentation of
all possible entries.
tests Regression tests which can be run by Kyua. See tests/README
for additional information.
tools Utilities for regression testing and miscellaneous tasks.
usr.bin User commands.
usr.sbin System administration commands.
For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see:
https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/current-stable.html