pcvis 0.3.0

2022-12-01

pcvis

A command line tool for visualizing page cache of a given file

prerequisites

• install pcstat (Page Cache stat: get page cache stats for files, https://github.com/tobert/pcstat)
  • it has both Linux and macOS binaries since v0.0.1

installation

via pip

pip install pcvis

After installation, there will be a command called pcvis you can use

manual

1. Download this repo, copy the pcvis/pcvis.py from this repo
2. Move pcvis.py into your $PATH (e.g. /usr/local/bin)

mv pcvis.py /usr/local/bin/pcvis
chmod +x /usr/local/bin/pcvis

usage

Visualize a given file's page cache status like below. In the visualized image, the white dots indicate the part of the file that is in the page cache.

# pcstat still needs to be installed, and it will be automatically launched by pcvis
pcvis -f /path/to/my_file

sample outputs

█░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░█░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░█░░░░░░░░░░░░░░░░░░░░█░░░░░░░░░█░░░░█░█░██░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░█

Via this visualization, you can easily spot that:

1. this file's header and footer are accessed and loaded in page cache
2. this file is accessed in a random access manner, and you may even vaguely check if the random access is a binary search, etc

arguments

• -f or --file: the path to the file you want to visualize its page cache status, e.g. pcvis -f /path/to/my_file. If you specify this argument, pcvis will launch pcstat automatically and visualize the result. If this argument is not specified, pcvis will read the output of pcstat from stdin, e.g. pcstat -json -pps /path/to/my_file | pcvis

• -s or --style: there are over 20 different rendering styles to choose from, you can specify a custom style by passing an integer to this argument. The default style is 0. Some sample styles are shown below:

  • e.g. pcvis -s 24 🌕🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌕🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌕🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌕🌑🌑🌑🌑🌑🌑🌑🌑🌑🌕🌑🌑🌑🌑🌕🌑🌕🌑🌕🌕🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌑🌕

  • e.g. pcvis -s 17 💚🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍💚🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍💚🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍💚🤍🤍🤍🤍🤍🤍🤍🤍🤍💚🤍🤍🤍🤍💚🤍💚🤍💚💚🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍🤍💚

• -h or --help: show help message

notes

1. Before running the above command for visualization, you need to clean page cache so that the above result is accurate

# for linux
sync; echo 1 > /proc/sys/vm/drop_caches 
# for macOS
sudo purge

2. Some of the icons in the visualization requires UTF8 to render, so you may need to set locale to UTF8 under some systems

export LC_ALL="en_US.utf8"