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many regions checked again and again despite knowing the pages contained were not usable and only satisfied the alignment constraints This case was compounded, especially for large allocations, by the practice of looping from the top of memory so as to keep out of the important low-memory regions. While the old contigmalloc(9) has the same problem, it is not as noticeable due to looping from the low memory to high. This degenerate case is fixed, as well as reversing the sense of the rest of the loops within it, to provide a tremendous speed increase. This makes the best case O(n * VM overhead) much more likely than the worst case O(4 * VM overhead). For comparison, the worst case for old contigmalloc would be O(5 * VM overhead) in addition to its strategy of turning used memory into free being highly pessimal. Also, fix a bug that in practice most likely couldn't have been triggered, int the new contigmalloc(9): it walked backwards from the end of memory without accounting for how many pages it needed. Potentially, nonexistant pages could have been mapped. This hasn't occurred because the kernel generally requests as its first contigmalloc(9) a single page. Reported by: Nicolas Dehaine <nicko@stbernard.com>, wes MFC After: 1 month More testing by: Nicolas Dehaine <nicko@stbernard.com>, wes
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ 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, the most commonly used one being ``world'', which rebuilds and installs everything in the FreeBSD system from the source tree except the kernel, the kernel-modules and the contents of /etc. The ``buildkernel'' and ``installkernel'' targets build and install the kernel and the modules (see below). Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html And in the config(8) man page. Note: If you want to build and install the kernel with the ``buildkernel'' and ``installkernel'' targets, you might need to build world before. More information is available in the handbook. The sample kernel configuration files reside in the sys/<arch>/conf sub-directory (assuming that you've installed the kernel sources), the file named GENERIC being the one used to build your initial installation kernel. The file NOTES contains entries and documentation for all possible devices, not just those commonly used. It is the successor of the ancient LINT file, but in contrast to LINT, it is not buildable as a kernel but a pure reference and documentation file. Source Roadmap: --------------- bin System/user commands. contrib Packages contributed by 3rd parties. crypto Cryptography stuff (see crypto/README). etc Template files for /etc. games Amusements. 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. sbin System commands. secure Cryptographic libraries and commands. share Shared resources. sys Kernel sources. 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: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html