.wasm binaries that we ship to clients over the network, such as our Game
of Life Web application, we want to keep an eye on code size. The smaller our
.wasm is, the faster our page loads get, and the happier our users are.
How small can we get our Game of Life
.wasm binary via build configuration?
With the default release build configuration (without debug symbols), our WebAssembly binary is 29,410 bytes:
$ wc -c pkg/wasm_game_of_life_bg.wasm 29410 pkg/wasm_game_of_life_bg.wasm
After enabling LTO, setting
opt-level = "z", and running
wasm-opt -Oz, the
.wasm binary shrinks to only 17,317 bytes:
$ wc -c pkg/wasm_game_of_life_bg.wasm 17317 pkg/wasm_game_of_life_bg.wasm
And if we compress it with
gzip (which nearly every HTTP server does) we get
down to a measly 9,045 bytes!
$ gzip -9 < pkg/wasm_game_of_life_bg.wasm | wc -c 9045
wasm-sniptool to remove the panicking infrastructure functions from our Game of Life's
.wasmbinary. How many bytes does it save?
Build our Game of Life crate with and without
wee_allocas its global allocator. The
rustwasm/wasm-pack-templatetemplate that we cloned to start this project has a "wee_alloc" cargo feature that you can enable by adding it to the
defaultkey in the
[features] default = ["wee_alloc"]
How much size does using
wee_allocshave off of the
We only ever instantiate a single
Universe, so rather than providing a constructor, we can export operations that manipulate a single
static mutglobal instance. If this global instance also uses the double buffering technique discussed in earlier chapters, we can make those buffers also be
static mutglobals. This removes all dynamic allocation from our Game of Life implementation, and we can make it a
#![no_std]crate that doesn't include an allocator. How much size was removed from the
.wasmby completely removing the allocator dependency?