Creating a sysimage for fast plotting with Plots.jl

!!! note Julia Version 1.9 Performance Update Starting from Julia 1.9, the "time to first plot" (TTFP) has seen a significant improvement due to the introduction of native code caching with Package Images. While the techniques presented in this guide for creating a custom sysimage remain applicable and beneficial for further optimization, please note that the relative improvement will be less dramatic due to the enhanced performance of code loading and execution in recent Julia versions.

A common complaint about Julia is that the "time to first plot" is a bit longer than desired. In this example, we will create a sysimage that is made to improve this.

To get a reference, we measure the time it takes to create the first plot with the default sysimage:

julia> @time using Plots
  2.943946 seconds (8.11 M allocations: 567.656 MiB, 6.47% gc time)

julia> @time p = plot(rand(2,2));
  1.940742 seconds (3.29 M allocations: 197.525 MiB, 4.65% gc time)

julia> @time display(p);
  5.132217 seconds (15.00 M allocations: 847.491 MiB, 2.57% gc time, 45.95%)

This is approximately 19 seconds from the start of Julia to the first plot.

We now create a precompilation file with exactly this workload in a file called precompile_plots.jl in the current directory:

using Plots
p = plot(rand(2,2))

The custom sysimage is then created as:

using PackageCompiler
create_sysimage(["Plots"], sysimage_path="", precompile_execution_file="precompile_plots.jl")

If we now start Julia with the flag --sysimage and re-time our previous commands:

julia> @time using Plots
  0.000159 seconds (1.07 k allocations: 79.797 KiB)

julia> @time p = plot(rand(2,2));
  0.037670 seconds (74.09 k allocations: 4.703 MiB)

julia> @time display(p);
  0.331869 seconds (278.38 k allocations: 7.900 MiB)

which is a sizeable speedup.

When using the sysimage, you may need to call Plots.__init__() after loading Plots for the plots to display; otherwise, you might need to use gui or pass argument show = true to plot.

Note that since we have more stuff in our sysimage, Julia is slightly slower to start (0.35 seconds on this machine):

# Default sysimage
➜ time julia -e ''                        
julia -e ''  0.06s user 0.06s system 130% cpu 0.088 total

# Custom sysimage
➜ time julia --sysimage -e ''
julia --sysimage -e ''  0.43s user 0.30s system 347% cpu 0.211 total