freebsd kernel with SKQ
53f78d1a7d
includes path-compression. This greatly helps with sparsely populated tries, where an uncompressed trie may end up by having a lot of intermediate nodes for very little leaves. The new algorithm introduces 2 main concepts: the node level and the node owner. Every node represents a branch point where the leaves share the key up to the level specified in the node-level (current level excluded, of course). Such key partly shared is the one contained in the owner. Of course, the root branch is exempted to keep a valid owner, because theoretically all the keys are contained in the space designed by the root branch node. The search algorithm seems very intuitive and that is where one should start reading to understand the full approach. In the end, the algorithm ends up by demanding only one node per insert and this is not necessary in all the cases. To stay safe, we basically preallocate as many nodes as the number of physical pages are in the system, using uma_preallocate(). However, this raises 2 concerns: * As pmap_init() needs to kmem_alloc(), the nodes must be pre-allocated when vm_radix_init() is currently called, which is much before UMA is fully initialized. This means that uma_prealloc() will dig into the UMA_BOOT_PAGES pool of pages, which is often not enough to keep track of such large allocations. In order to fix this, change a bit the concept of UMA_BOOT_PAGES and vm.boot_pages. More specifically make the UMA_BOOT_PAGES an initial "value" as long as vm.boot_pages and extend the boot_pages physical area by as many bytes as needed with the information returned by vm_radix_allocphys_size(). * A small amount of pages will be held in per-cpu buckets and won't be accessible from curcpu, so the vm_radix_node_get() could really panic when the pre-allocation pool is close to be exhausted. In theory we could pre-allocate more pages than the number of physical frames to satisfy such request, but as many insert would happen without a node allocation anyway, I think it is safe to assume that the over-allocation is already compensating for such problem. On the field testing can stand me correct, of course. This could be further helped by the case where we allow a single-page insert to not require a complete root node. The use of pre-allocation gets rid all the non-direct mapping trickery and introduced lock recursion allowance for vm_page_free_queue. The nodes children are reduced in number from 32 -> 16 and from 16 -> 8 (for respectively 64 bits and 32 bits architectures). This would make the children to fit into cacheline for amd64 case, for example, and in general spawn less cacheline, which may be helpful in lookup_ge() case. Also, path-compression cames to help in cases where there are many levels, making the fallouts of such change less hurting. Sponsored by: EMC / Isilon storage division Reviewed by: jeff (partially) Tested by: flo |
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| bin | ||
| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| ObsoleteFiles.inc | ||
| README | ||
| UPDATING | ||
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 ``world'' target should only be used in cases where the source tree has not changed from the currently running version. See: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html for more information, including setting make(1) variables. 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. 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. 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. rescue Build system for statically linked /rescue utilities. 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