d94a2a2088
multiple unmapped pages. Unmapped mbufs allow sendfile to carry multiple pages of data in a single mbuf, without mapping those pages. It is a requirement for Netflix's in-kernel TLS, and provides a 5-10% CPU savings on heavy web serving workloads when used by sendfile, due to effectively compressing socket buffers by an order of magnitude, and hence reducing cache misses. For this new external mbuf buffer type (EXT_PGS), the ext_buf pointer now points to a struct mbuf_ext_pgs structure instead of a data buffer. This structure contains an array of physical addresses (this reduces cache misses compared to an earlier version that stored an array of vm_page_t pointers). It also stores additional fields needed for in-kernel TLS such as the TLS header and trailer data that are currently unused. To more easily detect these mbufs, the M_NOMAP flag is set in m_flags in addition to M_EXT. Various functions like m_copydata() have been updated to safely access packet contents (using uiomove_fromphys()), to make things like BPF safe. NIC drivers advertise support for unmapped mbufs on transmit via a new IFCAP_NOMAP capability. This capability can be toggled via the new 'nomap' and '-nomap' ifconfig(8) commands. For NIC drivers that only transmit packet contents via DMA and use bus_dma, adding the capability to if_capabilities and if_capenable should be all that is required. If a NIC does not support unmapped mbufs, they are converted to a chain of mapped mbufs (using sf_bufs to provide the mapping) in ip_output or ip6_output. If an unmapped mbuf requires software checksums, it is also converted to a chain of mapped mbufs before computing the checksum. Submitted by: gallatin (earlier version) Reviewed by: gallatin, hselasky, rrs Discussed with: ae, kp (firewalls) Relnotes: yes Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D20616 |
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config | ||
etc | ||
include | ||
libgloss | ||
newlib | ||
texinfo | ||
winsup | ||
.drone.yml | ||
.gitattributes | ||
.gitignore | ||
COPYING | ||
COPYING.LIB | ||
COPYING.LIBGLOSS | ||
COPYING.NEWLIB | ||
COPYING3 | ||
COPYING3.LIB | ||
ChangeLog | ||
MAINTAINERS | ||
Makefile.def | ||
Makefile.in | ||
Makefile.tpl | ||
README | ||
README-maintainer-mode | ||
compile | ||
config-ml.in | ||
config.guess | ||
config.rpath | ||
config.sub | ||
configure | ||
configure.ac | ||
depcomp | ||
djunpack.bat | ||
install-sh | ||
libtool.m4 | ||
ltgcc.m4 | ||
ltmain.sh | ||
ltoptions.m4 | ||
ltsugar.m4 | ||
ltversion.m4 | ||
lt~obsolete.m4 | ||
makefile.vms | ||
missing | ||
mkdep | ||
mkinstalldirs | ||
move-if-change | ||
setup.com | ||
src-release | ||
symlink-tree | ||
ylwrap |
README
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.