Zero-copy!
This is both CPU and GPU main memory. How to avoid copying buffers from and to the same memory?
// note: buffer_size is re-written in place
void *zerocopy_alloc(size_t &buffer_size)
{
// OpenCL zero-copy buffers need to be aligned on a page size (i.e., 4KB),
// and the allocated …pocl will convert your opencl kernels into AVX-vectorized CPU binaries
pocl stands for portable compute language [1].
For sweet and crispy pocl, you'll need:
- warm up your favorite C++ compiler
- prepare the follow baking packages (if you have an Ubuntu 16.04 kitchen)
# llvm clang 5.0 or …
What's possible with OpenCL 2.0 today?
AMDGPU-PRO is the closed-source implementation of OpenCL 2.x for AMD. It only targets AMD GPU. AMD used to provided a CPU target, but it is OpenCL 1.2 only.
rocm is the heterogeneous computing effort of AMD, and is open-source. It …
Trying to build the latest lldb.
A good introduction about lldb is this presentation at the Apple developper conference [1]. For something more focused on ARM, see [2], and for something more focused on FreeBSD, see [3] and [4].
The official build guide is [5]. There are …
Trying to build the latest GNU gdb on Scaleway ARM instance.
Build command:
apt install bison flex configure --with-python --without-ncurses --enable-targets=all --prefix=/opt/gdb make -j4
Neither the version 7.12 nor 8.1 (or even the git sources [1]) build out-of-the-box, while there are no issues on x86_64 …
read moreTODO
| [1] | Fetch, "Living standard", https://fetch.spec.whatwg.org |
| [2] | Google Chrome, "Fetch API example", https://github.com/GoogleChrome/samples/blob/gh-pages/fetch-api/fetch-response-stream.html |
| [3] | StackOverflow, "Javascript - Using Promises on Websocket?", https://stackoverflow.com/questions/42304996/javascript-using-promises-on-websocket |
| [4] | https://github.com/vitalets/websocket-as-promised |
| [5] | https://developers.google … |
Old school internet!
There is some trickery because of the Raspberry 3 bluetooth feature. See [1].
By default, the nice hardware serial port /dev/ttyAMA0 is dedicated to the bluetooth connection.
Disable bluetooth in /boot/config.txt:
dtoverlay=pi3-disable-bt
Disable kernel use of the serial port by removing from /boot …
read moreWouldn't it be nice to let people play with gdb and inapp from the internet?
Yeah, but wait a minute, people would take control of the host computer and use its network connectivity of other and unintended purposes. Especially since the demo gives you access to a working gdb session …
read moreHowto download a binary as a stream using javascript?
It may look easy to do with good old XMLHttpRequest, but actually, it is not as obvious. In binary mode, the response object returned by XMLHttpRequest is always complete. Chunked responses are only possible using non-standard moz-chunked-arraybuffer transfer mode (only support …
read moreActivate readline menu-complete, back-menu-complete, and keep normal 'tab' completion.
Normal complete style is the one expected to happen when hitting Tab on any Linux distribution.
menu-complete style is the one expected to happen on MS-DOS. This one is more convenient when using a gamepad as input, since …
FriendlyARM has an image for the NanoPi NEO with mainline linux kernel.
Look! There is a 4.11 kernel image packed with Ubuntu 16.04 (see [1]).
Unfortunately, the image does not support docker out-of-the-box, because the kernel was not built with the required options.
The flag …
The conversion from DTS to DTB and back to DTS.
In the Linux kernel source tree, there are .dts (i.e., device tree source) and .dtsi (i.e., device tree source include).
.dtb is the binary form of the .dts in a similar sense what a binary exectuable is …
Back to DOS!
Let's mix everything together~
Install qemu:
apt install qemu [...] qemu-img create -f raw freedos.img 100M …
The long awaited quest of the USB On-the-Go with mainline Linux kernel 4.x.
As already documented here before, it is possible to configure FriendlyARM's NanoPi Neo to behave as an USB Ethernet/RNDIS gadget device. Unfortunately this functionality relied on legacy/hacked sunxi kernel. This kernel (3.x …
The FrameDecorator example given in the documentation does not work?
If you naïvely try the implement your own MyFrameFilter following the example of the InlineFilter given in the gdb (holy?) documentation [1], you may face the following python errors.
class MyFrameDecorator(FrameDecorator): TypeError: Error when calling the metaclass …
How to begin with nginx?
Easy, just start at the beginners' guide [1].
user www-data;
pid /run/nginx.pid;
http {
# Basic Settings
sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
include /etc/nginx/mime.types;
default_type application/octet-stream;
# Logging Settings
access_log /var/log/nginx/access.log;
error_log /var …How to start a parameterized task on a jenkins server with curl?
The answer to this question seems simple at first after seen this page [1]. Unfortunately, it does not work as described:
vjp@inabox:~$ curl -i -X POST http://localhost:8080/job/inapp_GenerateDocs/build --form file0 …
How to run a docker container from another docker container?
Create a docker image which runs jenkins. A jenkins task will prepare a data folder to be used along with another docker container. At the end the two containers will run side by side. The container spawned by the jenkins …
read more
Keywords: inapp, pretty print, parser, websocket, distributed
| [1] | presentation https://vjordan.info/ina/expo/galerie |
| [2] | use-case https://ina.vjordan.info |
| [3] | sources, https://git.vjordan.info/vjp/inapp2 |
| [4] | tutorial/game, The Legend of Ina, soon (https://vjordan.info/log/fpga/ina-unboxing.html) |
You have your shinny new Jenkins installation, but how to make it more personal? How to change the logo of Jenkins?
The butler face is nice, but what if I wanted to add something to the logo?
In <jenkins_home>, there is an interesting file named title.png coming …
Store and load a docker image from USB storage.
# docker save -o /mnt/docker/inapp-v0.1-armhf.tar inapp # ls -l /mnt/docker/inapp-v0.1-armhf.tar -rwxr-xr-x 1 root root 212420096 Mar 28 19:27 /mnt/docker/inapp-v0.1-armhf.tar # docker load -i /mnt/docker/inapp-v0.1-armhf.tar Loaded image: inapp …read more
Build a docker container for inapp.
Run a Debian image for tests:
sudo docker run -ti --rm debian:jessie-slim bash
...and validate the build sequence:
apt-get update apt-get install make apt-get install g++ apt-get install qtbase5-dev apt-get install libqt5websockets5-dev apt-get install liblttng-ust-dev apt-get install …
Is it possible to run docker containers on NanoPi NEO?
Your Linux kernel version 3.4.113-sun8i is not supported for running docker. Please upgrade your kernel to 3.10.0 or newer.
Unfortuntely no, it does not work with the default legacy kernel 3.4.113-sun8i.
Preparing JSON files from command-line using Python base library.
Python has a library to process JSON by default. See [1].
Using Python on command-line, simple scripts can be written for preparing JSON configurations (e.g., with a Makefile).
Want to stringify a JSON file in order to embedded it …
Installing inapp on Armbian.
Update everything after the fresh installation to get the latest kernel and packages:
apt-get update apt-get upgrade
Disable the NetworkManager deamon and save ~6MB of RAM:
root@nanopineo:~# systemctl disable NetworkManager Removed symlink /etc/systemd/system/dbus-org.freedesktop.nm-dispatcher.service. Removed symlink /etc/systemd/system/multi-user …read more
Now the operating system. Take two with Armbian.
Get the OS image Armbian_5.25_Nanopineo_Ubuntu_xenial_default_3.4.113.7z at [1].
Write the image to the SD-card (4GB min):
sudo dd if=Armbian_5.25_Nanopineo_Ubuntu_xenial_default_3.4.113.img of=/dev/mmcblk0 …
Now the operating system. Take one with the official image from FriendlyArm.
Get the OS image nanopi-neo-ubuntu-core-qte-sd4g-20170204.img.zip at [1].
Write the image to the SD-card (4GB min):
sudo dd if=nanopi-neo-ubuntu-core-qte-sd4g-20170204.img of=/dev/mmcblk0 bs …
Cute little ARM board (inner active ingredient) + Tiny 3D-printed housing (color plastic hull) + Transparent sticker (attractive branding) = your new medication for pretty printing.
The Nano Pi Neo is a cheap Chinese ARM board with everything needed (Ethernet, On-the-Go USB) and a tiny 40x40mm form-factor [1].
The …
How to serve a website by merging multiple base folders?
mod_alias is the answer! [1]
/opt/ina/all/www/
term/www/
cli/www/
pp/www/
dbg/www/
alias.url += ( "/all" => "/opt/ina/all/www/" ) alias.url += ( "/term" => "/opt/ina/term/www/" ) [...]
/etc/lighttpd/conf-available/50-inaterm.conf:
server.modules += ( "mod_alias" ) alias …read more
How to create a systemd-friendly QWebSocket server?
Surprisingly, there does not seem to be any official Qt documentation for this use-case. Enjoy.
The keyword here is socket-based activation. [1]
systemd will create the socket first and listen to incoming connections. On first incoming connection, the …
What is this timestamp in each kernel printk message?
Quote from [1].
Printk-time uses the routine sched_clock() in the kernel. On some platforms, sched_clock() only has a resolution of 1 jiffy (which may be 10 milliseconds or longer). This means that you will only see the time increment at this …read more
Prepare a Debian virtual image to build packages.
Get the netinstall 248MB image (e.g., debian-8.7.1-amd64-netinst.iso) at this address [1], and start a new virtualbox machine.
Only need a minimalistic system.
Ready!
A short introduction …
Highly insecure!
Create a user with a password, and delete it later ([1]):
root@inabox:/home/ina# adduser test [...give a password...] root@inabox:/home/ina# passwd -d test passwd: password expiry information changed.
In /etc …
Initial example for setting a kernel tracepoint and forward the trace output over DLT (Autosar Diagnostic Log and Trace).
This example is taken straight out of the Linux kernel documentation at [1]. For details about the kprobes internals, see [2].
# The tracing facility is in the …
https://wiki.linuxfoundation.org/images/1/1c/Network_data_flow_through_kernel.png https://wiki.linuxfoundation.org/networking/kernel_flow
perf uses kprobes/uprobes for dynamique tracing.
perf for Performance counter …
read moreHow do Linux kernel probes (kprobes) work
Everything below comes from reading kprobes.txt at [1].
There are kprobes and jprobes. jprobes are specialized kprobes for function calls, making it easier to get the function parameters. It is usually useful to filter function call traces according to the value …
What else is happening again?
(process:704): GLib-WARNING **: poll(2) failed due to: Invalid argument.
$ sysctl net.core.somaxconn net.core.somaxconn = 128
$ find /usr/include -name socket.h /usr/include/asm-generic/socket.h /usr/include/linux/socket.h /usr/include/x86_64-linux-gnu/bits/socket.h /usr/include/x86_64-linux-gnu …
But wait! What happens when I use Chinese input? ...types CTRL+Space and start composing... Oh shit!~ [1]
Capturing key strokes is nice, but it does not support virtual keyboard like on tablet or smartphones and more advanced input methods such as Chinese/Japanese or other writing systems.
The problem …
read more
std::string l;
// Read lines here
while(std::getline(std::cin, l))
{
// Send Unicode string
emit newLine(QString::fromStdString(l));
}
This works because \n (newline) is a single byte in UTF-8.
char c;
// Read bytes here
while(std::cin.get(c))
{
// Send Unicode single …A story which begins on the keyboard, goes through a pseudo-terminal, and ends up on the screen.
Now that you love ptypipe (see previous post), we are ready to pipe everything and finally control gdb:
$ makefifo input.cli $ python ptypipe.py "" "gdb -q" < input.cli | myGreatControlProgram > input.cli
You can pipe commands to gdb, but how to have auto-complete on those commands?
A initial little try is promising, we can pipe commands to gdb:
~$ echo "show endian" | gdb -q (gdb) The target endianness is set automatically (currently little endian) (gdb) quit
The command show endian was …
Questioning about the "target triplet" <CPU>-<vendor>-<OS> used by the GNU build system to describe a target
When building gdb targeting a different platform, one must choose --host, --build, and --target parameters.
The target parameter has the following format [1]:
<CPU>-<vendor>-<OS>
You can get the target of …
read moreMany websites host HTML rendering of man pages. How to make them yourself?
Stackoverflow always has an answer for those questions [1].
A tool without many dependencies is mandoc [2], and of course, it has its mandatory HTML man page there [3].
./configure make ./mandoc -Thtml -Ostyle=mandoc.css ../man-pages-4 …read more
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