freebsd with flexible iflib nic queues
252ca42863
to read-locking in the TCP input path, allowing greater TCP input parallelism where multiple ithreads or ithread and netisr are able to run in parallel. Previously, most TCP input paths held a write lock on the global tcbinfo lock, effectively serializing TCP input. Before looking up the connection, acquire a write lock if a potentially state-changing flag is set on the TCP segment header (FIN, RST, SYN), and otherwise a read lock. We may later have to upgrade to a write lock in certain cases (ACKs received by the syncache or during TIMEWAIT) in order to support global state transitions, but this is never required for steady-state packets. Upgrading from a write lock to a read lock must be done as a trylock operation to avoid deadlocks, and actually violates the lock order as the tcbinfo lock preceeds the inpcb lock held at the time of upgrade. If the trylock fails, we bump the refcount on the inpcb, drop both locks, and re-acquire in-order. If another thread has freed the connection while the locks are dropped, we free the inpcb and repeat the lookup (this should hardly ever or never happen in practice). For now, maintain a number of new counters measuring how many times various cases execute, and in particular whether various optimistic assumptions about when read locks can be used, whether upgrades are done using the fast path, and whether connections close in practice in the above-described race, actually occur. MFC after: 6 weeks Discussed with: kmacy Reviewed by: bz, gnn, kmacy Tested by: kmacy |
||
|---|---|---|
| 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. 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