Disable garbage collection temporary

[leiserfg]

Hey @L3MON4D3 I was playing with some optimizations and noticed that disabling the garbage collection while loading vscode snippets (and enabling it after) reduces the time of loading noticeably. The change is more noticeable when using the synchronous load.

[L3MON4D3]

Interesting! Any downsides to doing that? Do you have some numbers/flamegraph?

[leiserfg]

Potential downsides:

• the user has not enough ram to hold all the stuff at once
• something crashes and we don't re-enable the GC so nvim keeps eating ram forever.

For my measurements, loading goes from btw 0.47 and 0.50 to 0.30

The 0.3 is including the step of re-enabling the GC

[L3MON4D3]

Oh, yeah 1 makes sense, ofc
2 is a good point, the most straightforward way to guarantee this seems to be something like

local no_gc_load = function(...)
    collectgarbage "stop"
    local ok, res = pcall(load, ...)
    collectgarbage "restart"
    if not ok then
        error(res)
    end
end

This kind of begs the question if we should just provide a generic interface to this,
where any function can be passed.
But for now, explicit functions without gc seem more comfortable.

[leiserfg]

I was trying to profile it, but unfortunately, I could not make it work, the luajit included in nvim for nixos does not include "jit.profile". Can you do it?

local prof = require'plenary.profile'

prof.start("/tmp/no_gc_profile.log")
-- collectgarbage "stop"
require("luasnip/loaders/from_vscode").load()
-- collectgarbage "restart"
prof.stop()

local prof = require'plenary.profile'

prof.start("/tmp/gc_profile.log")
collectgarbage "stop"
require("luasnip/loaders/from_vscode").load()
collectgarbage "restart"
prof.stop()

[L3MON4D3]

Yes!
with GC:

without GC:

Looks like everything is just faster, nothing in particular catches my eye (I guess that would be expected, more or less?)

Looking at that flamegraph, I think both the deepcopies and complete_ext_opts could be optimized quite a bit (though not as easily as just turning of garbage collection for a bit)

[leiserfg]

I'm actually doing it for my complete config, it helps not only with luasnip:

collectgarbage "stop"
-- jit.off()

vim.api.nvim_create_autocmd("InsertEnter", {
  callback = function()
    -- jit.on()
    collectgarbage "restart"
  end,
  once = true,
})

as you can see I was also playing with disabling the jit, that helps with some plugins but makes it slower for others tho.