Some experiments concerning the performance of Linux pipes. Please head to the blog post to understand what this code is about.
Building and running
% make
% ./write | ./read
4.5GiB/s, 256KiB buffer, 40960 iterations (10GiB piped)
./read reads 10GiB (by default). Use --csv for machine-readable output with this schema:
gigabytes_per_second,bytes_to_pipe,buf_size,pipe_size,busy_loop,poll,huge_page,check_huge_page,write_with_vmsplice,read_with_splice,gift,lock_memory,dont_touch_pages,same_buffer
Where the first four are numbers and the rest are booleans. All the fields apart from gigabytes_per_seconds (which is the main output of the program) are configurable on the command line. Check out parse_options in common.hpp.
measure.py can be ran to automatically produce the data shown in the graph at the top of the blog post. It requires taskset, and various python libraries. If you have nix:
% nix-shell
% python3 measure.py
Additionally, get-user-pages.cpp contains a small benchmark using /sys/kernel/debug/gup_test. To run it, you need to compile your kernel with CONFIG_GUP_TEST y. Also, the file and flag were recently renamed, prior to kernel version 5.17 they were called gup_benchmark and CONFIG_GUP_BENCHMARK, respectively.