freebsd kernel with SKQ
b2f095aaa6
a) Front load as much work as possible in if_transmit, before any driver lock or software queue has to get involved. b) Replace buf_ring with a brand new mp_ring (multiproducer ring). This is specifically for the tx multiqueue model where one of the if_transmit producer threads becomes the consumer and other producers carry on as usual. mp_ring is implemented as standalone code and it should be possible to use it in any driver with tx multiqueue. It also has: - the ability to enqueue/dequeue multiple items. This might become significant if packet batching is ever implemented. - an abdication mechanism to allow a thread to give up writing tx descriptors and have another if_transmit thread take over. A thread that's writing tx descriptors can end up doing so for an unbounded time period if a) there are other if_transmit threads continuously feeding the sofware queue, and b) the chip keeps up with whatever the thread is throwing at it. - accurate statistics about interesting events even when the stats come at the expense of additional branches/conditional code. The NIC txq lock is uncontested on the fast path at this point. I've left it there for synchronization with the control events (interface up/down, modload/unload). c) Add support for "type 1" coalescing work request in the normal NIC tx path. This work request is optimized for frames with a single item in the DMA gather list. These are very common when forwarding packets. Note that netmap tx in cxgbe already uses these "type 1" work requests. d) Do not request automatic cidx updates every 32 descriptors. Instead, request updates via bits in individual work requests (still every 32 descriptors approximately). Also, request an automatic final update when the queue idles after activity. This means NIC tx reclaim is still performed lazily but it will catch up quickly as soon as the queue idles. This seems to be the best middle ground and I'll probably do something similar for netmap tx as well. e) Implement a faster tx path for WRQs (used by TOE tx and control queues, _not_ by the normal NIC tx). Allow work requests to be written directly to the hardware descriptor ring if room is available. I will convert t4_tom and iw_cxgbe modules to this faster style gradually. MFC after: 2 months |
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| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tests | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| .arcconfig | ||
| .arclint | ||
| 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