freebsd kernel with SKQ
0d4e4e5ea4
The symptom: sometimes 11n (and non-11n) throughput is great.
Sometimes it isn't. Much teeth gnashing occured, and much kernel
bisecting happened, until someone figured out it was the order
of which things were rebooted, not the kernel versions.
(Which was great news to me, it meant that I hadn't broken if_ath.)
What we found was that sometimes the WME parameters for the best-effort
queue had a burst window ("txop") in which the station would be allowed
to TX as many packets as it could fit inside that particular burst
window. This improved throughput.
After initially thinking it was a bug - the WME parameters for the
best-effort queue -should- have a txop of 0, Bernard and I discovered
"aggressive mode" in net80211 - where the WME BE queue parameters
are changed if there's not a lot of high priority traffic going on.
The WME parameters announced in the association response and beacon
frames just "change" based on what the current traffic levels are.
So in fact yes, the STA was acutally supposed to be doing this higher
throughput stuff as it's just meant to be configuring things based on
the WME parameters - but it wasn't.
What was eventually happening was this:
* at startup, the wme qosinfo count field would be 0;
* it'd be parsed in ieee80211_parse_wmeparams();
* and it would be bumped (to say 10);
* .. and the WME queue parameters would be correctly parsed and set.
But then, when you restarted the assocation (eg hostap goes away and
comes back with the same qosinfo count field of 10, or if you
destroy the sta VIF and re-create it), the WME qosinfo count field -
which is associated not to the VIF, but to the main interface -
wouldn't be cleared, so the queue default parameters would be used
(which include no burst setting for the BE queue) and would remain
that way until the hostap qosinfo count field changed, or the STA
was actually rebooted.
This fix simply cleares the wme capability field (which has the count
field) to 0, forcing it to be reset by the next received beacon.
Thanks go to Milu for finding it and helping me track down what was
going on, and Bernard Schmidt for working through the net80211 and
WME specific magic.
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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 | ||
| Makefile.mips | ||
| 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