b16b4c22d2
FreeBSD's boot times have decreased to the point where vm_page array initialization represents a significant fraction of the total boot time. For example, when booting FreeBSD in Firecracker (a VMM designed to support lightweight VMs) with 128MB and 1GB of RAM, vm_page initialization consumes 9% (3ms) and 37% (21.5ms) of the kernel boot time, respectively. This is generally relevant in cloud environments, where one wants to be able to spin up VMs as quickly as possible. This patch implements lazy initialization of (most) page structures, following a suggestion from cperciva@. The idea is to introduce a new free pool, VM_FREEPOOL_LAZYINIT, into which all vm_page structures are initially placed. For this to work, we need only initialize the first free page of each chunk placed into the buddy allocator. Then, early page allocations draw from the lazy init pool and initialize vm_page chunks (up to 16MB, 4096 pages) on demand. Once APs are started, an idle-priority thread drains the lazy init pool in the background to avoid introducing extra latency in the allocator. With this scheme, almost all of the initialization work is moved out of the critical path. A couple of vm_phys operations require the pool to be drained before they can run: vm_phys_find_range() and vm_phys_unfree_page(). However, these are rare operations. I believe that vm_phys_find_freelist_contig() does not require any special treatment, as it only ever accesses the first page in a power-of-2-sized free page chunk, which is always initialized. For now the new pool is only used on amd64 and arm64, since that's where I can easily test and those platforms would get the most benefit. Reviewed by: alc, kib Differential Revision: https://reviews.freebsd.org/D40403 |
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.cirrus-ci | ||
.github | ||
bin | ||
cddl | ||
contrib | ||
crypto | ||
etc | ||
gnu | ||
include | ||
kerberos5 | ||
lib | ||
libexec | ||
release | ||
rescue | ||
sbin | ||
secure | ||
share | ||
stand | ||
sys | ||
targets | ||
tests | ||
tools | ||
usr.bin | ||
usr.sbin | ||
.arcconfig | ||
.arclint | ||
.cirrus.yml | ||
.clang-format | ||
.git-blame-ignore-revs | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
CONTRIBUTING.md | ||
COPYRIGHT | ||
LOCKS | ||
MAINTAINERS | ||
Makefile | ||
Makefile.inc1 | ||
Makefile.libcompat | ||
Makefile.sys.inc | ||
ObsoleteFiles.inc | ||
README.md | ||
RELNOTES | ||
UPDATING |
README.md
FreeBSD Source:
This is the top level of the FreeBSD source directory.
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), FreeBSD handbook on building userland, and Handbook for kernels for more information, including setting make(1) variables.
For information on the CPU architectures and platforms supported by FreeBSD, see the FreeBSD website's Platforms page.
For official FreeBSD bootable images, see the release page.
Source Roadmap:
Directory | Description |
---|---|
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 | Commands and libraries under the GNU General Public License (GPL) or Lesser General Public License (LGPL). Please see gnu/COPYING and gnu/COPYING.LIB 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 (see sys/README.md). |
targets | Support for experimental DIRDEPS_BUILD |
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 FreeBSD Handbook.