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Linux kernel modifications for the Kernel Hacking exam
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Vincent Bernat feca7d8c13 net: ipv6: avoid overhead when no custom FIB rules are installed 
If the user hasn't installed any custom rules, don't go through the
whole FIB rules layer. This is pretty similar to f4530fa574 (ipv4:
Avoid overhead when no custom FIB rules are installed).

Using a micro-benchmark module [1], timing ip6_route_output() with
get_cycles(), with 40,000 routes in the main routing table, before this
patch:

    min=606 max=12911 count=627 average=1959 95th=4903 90th=3747 50th=1602 mad=821
    table=254 avgdepth=21.8 maxdepth=39
    value │                         ┊                            count
      600 │▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒                                         199
      880 │▒▒▒░░░░░░░░░░░░░░░░                                      43
     1160 │▒▒▒░░░░░░░░░░░░░░░░░░░░                                  48
     1440 │▒▒▒░░░░░░░░░░░░░░░░░░░░░░░                               43
     1720 │▒▒▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░                          59
     2000 │▒▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░                      50
     2280 │▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░                    26
     2560 │▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░                  31
     2840 │▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░               28
     3120 │▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░              17
     3400 │▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░             17
     3680 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░             8
     3960 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░           11
     4240 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░            6
     4520 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░           6
     4800 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░           9

After:

    min=544 max=11687 count=627 average=1776 95th=4546 90th=3585 50th=1227 mad=565
    table=254 avgdepth=21.8 maxdepth=39
    value │                         ┊                            count
      540 │▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒                                        201
      800 │▒▒▒▒▒░░░░░░░░░░░░░░░░                                    63
     1060 │▒▒▒▒▒░░░░░░░░░░░░░░░░░░░░░                               68
     1320 │▒▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░                            39
     1580 │▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░                         32
     1840 │▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░                       32
     2100 │▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░                    34
     2360 │▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░                 33
     2620 │▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░               26
     2880 │▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░              22
     3140 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░              9
     3400 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░             8
     3660 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░             9
     3920 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░            8
     4180 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░           8
     4440 │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░           8

At the frequency of the host during the bench (~ 3.7 GHz), this is
about a 100 ns difference on the median value.

A next step would be to collapse local and main tables, as in
0ddcf43d5d (ipv4: FIB Local/MAIN table collapse).

[1]: https://github.com/vincentbernat/network-lab/blob/master/lab-routes-ipv6/kbench_mod.c

Signed-off-by: Vincent Bernat <vincent@bernat.im>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-08 21:40:08 -07:00
arch mlx5-shared-2017-08-07 2017-08-07 10:42:09 -07:00
block blk-mq: map queues to all present CPUs 2017-07-24 10:01:31 -06:00
certs modsign: add markers to endif-statements in certs/Makefile 2017-07-14 11:01:37 +10:00
crypto crypto: authencesn - Fix digest_null crash 2017-07-18 17:01:11 +08:00
Documentation Documentation: describe the new eBPF verifier value tracking behaviour 2017-08-08 17:51:35 -07:00
drivers isdn: hfcsusb: constify usb_device_id 2017-08-08 21:38:27 -07:00
firmware firmware/Makefile: force recompilation if makefile changes 2017-05-08 17:15:10 -07:00
fs mlx5-shared-2017-08-07 2017-08-07 10:42:09 -07:00
include net: ipv6: avoid overhead when no custom FIB rules are installed 2017-08-08 21:40:08 -07:00
init random: do not ignore early device randomness 2017-07-12 16:26:00 -07:00
ipc ipc: add missing container_of()s for randstruct 2017-08-02 17:16:12 -07:00
kernel bpf: Extend check_uarg_tail_zero() checks 2017-08-08 18:11:17 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-08-01 10:07:50 -07:00
mm mm: take memory hotplug lock within numa_zonelist_order_handler() 2017-08-02 17:16:11 -07:00
net net: ipv6: avoid overhead when no custom FIB rules are installed 2017-08-08 21:40:08 -07:00
samples bpf: add a test case for syscalls/sys_{enter|exit}_* tracepoints 2017-08-07 14:09:48 -07:00
scripts DeviceTree fixes for 4.13: 2017-07-28 17:21:41 -07:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-07-21 03:38:43 +01:00
sound ASoC: Fixes for v4.13 2017-08-02 17:11:45 +02:00
tools selftests: bpf: add a test for XDP redirect 2017-08-08 18:12:50 -07:00
usr ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk. 2017-07-06 16:24:30 -07:00
virt KVM/ARM Fixes for v4.13-rc4 2017-08-03 17:59:58 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap power supply and reset changes for the v4.12 series (part 2) 2017-05-12 12:02:21 -07:00
COPYING
CREDITS avr32: remove support for AVR32 architecture 2017-05-01 09:27:15 +02:00
Kbuild kbuild: Consolidate header generation from ASM offset information 2017-04-13 05:43:37 +09:00
Kconfig
MAINTAINERS mlx5-shared-2017-08-07 2017-08-07 10:42:09 -07:00
Makefile Linux 4.13-rc4 2017-08-06 18:44:49 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.