This sample program show how to use cpumap and the associated
tracepoints.
It provides command line stats, which shows how the XDP-RX process,
cpumap-enqueue and cpumap kthread dequeue is cooperating on a per CPU
basis. It also utilize the xdp_exception and xdp_redirect_err
transpoints to allow users quickly to identify setup issues.
One issue with ixgbe driver is that the driver reset the link when
loading XDP. This reset the procfs smp_affinity settings. Thus,
after loading the program, these must be reconfigured. The easiest
workaround it to reduce the RX-queue to e.g. two via:
# ethtool --set-channels ixgbe1 combined 2
And then add CPUs above 0 and 1, like:
# xdp_redirect_cpu --dev ixgbe1 --prog 2 --cpu 2 --cpu 3 --cpu 4
Another issue with ixgbe is that the page recycle mechanism is tied to
the RX-ring size. And the default setting of 512 elements is too
small. This is the same issue with regular devmap XDP_REDIRECT.
To overcome this I've been using 1024 rx-ring size:
# ethtool -G ixgbe1 rx 1024 tx 1024
V3:
- whitespace cleanups
- bpf tracepoint cannot access top part of struct
V4:
- report on kthread sched events, according to tracepoint change
- report average bulk enqueue size
V5:
- bpf_map_lookup_elem on cpumap not allowed from bpf_prog
use separate map to mark CPUs not available
V6:
- correct kthread sched summary output
V7:
- Added a --stress-mode for concurrently changing underlying cpumap
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
eBPF sample programs
====================
This directory contains a test stubs, verifier test-suite and examples
for using eBPF. The examples use libbpf from tools/lib/bpf.
Build dependencies
==================
Compiling requires having installed:
* clang >= version 3.4.0
* llvm >= version 3.7.1
Note that LLVM's tool 'llc' must support target 'bpf', list version
and supported targets with command: ``llc --version``
Kernel headers
--------------
There are usually dependencies to header files of the current kernel.
To avoid installing devel kernel headers system wide, as a normal
user, simply call::
make headers_install
This will creates a local "usr/include" directory in the git/build top
level directory, that the make system automatically pickup first.
Compiling
=========
For building the BPF samples, issue the below command from the kernel
top level directory::
make samples/bpf/
Do notice the "/" slash after the directory name.
It is also possible to call make from this directory. This will just
hide the the invocation of make as above with the appended "/".
Manually compiling LLVM with 'bpf' support
------------------------------------------
Since version 3.7.0, LLVM adds a proper LLVM backend target for the
BPF bytecode architecture.
By default llvm will build all non-experimental backends including bpf.
To generate a smaller llc binary one can use::
-DLLVM_TARGETS_TO_BUILD="BPF"
Quick sniplet for manually compiling LLVM and clang
(build dependencies are cmake and gcc-c++)::
$ git clone http://llvm.org/git/llvm.git
$ cd llvm/tools
$ git clone --depth 1 http://llvm.org/git/clang.git
$ cd ..; mkdir build; cd build
$ cmake .. -DLLVM_TARGETS_TO_BUILD="BPF;X86"
$ make -j $(getconf _NPROCESSORS_ONLN)
It is also possible to point make to the newly compiled 'llc' or
'clang' command via redefining LLC or CLANG on the make command line::
make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
Cross compiling samples
-----------------------
In order to cross-compile, say for arm64 targets, export CROSS_COMPILE and ARCH
environment variables before calling make. This will direct make to build
samples for the cross target.
export ARCH=arm64
export CROSS_COMPILE="aarch64-linux-gnu-"
make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
fad3917e36