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Enable v8 snapshots

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There are two layers here. The first is that, on startup, a v8 SnapshotCreator
is created, and a snapshot-specific isolate/context is setup with our browser
environment. This contains most of what was in Env.init and a good chunk of
what was in ExecutionWorld.createContext. From this, we create a v8.StartupData
which is used for the creation of all subsequent contexts. The snapshot sits
at the application level, above the Env - it's re-used for all envs/isolates, so
this gives a nice performance boost for both 1 connection opening multiple pages
or multiple connections opening 1 page.

The second layer is that the Snapshot data can be embedded into the binary, so
that it doesn't have to be created on startup, but rather created at build-time.
This improves the startup time (though, I'm not really sure how to measure that
accurately...).

The first layer is the big win (and just works as-is without any build / usage
changes).

with snapshot
total runs 1000
total duration (ms) 7527
avg run duration (ms) 7
min run duration (ms) 5
max run duration (ms) 41

without snapshot
total runs 1000
total duration (ms) 9350
avg run duration (ms) 9
min run duration (ms) 8
max run duration (ms) 42

To embed a snapshot into the binary, we first need to create the snapshot file:

zig build -Doptimize=ReleaseFast snapshot_creator -- src/snapshot.bin

And then build using the new snapshot_path argument:

zig build -Dsnapshot_path=../../snapshot.bin -Doptimize=ReleaseFast

The paths are weird, I know...since it's embedded, it needs to be inside the
project path, hence we put it in src/snapshot.bin. And since it's embedded
relative to the embedder (src/browser/js/Snapshot.zig) the path has to be
relative to that, hence ../../snapshot.bin. I'm open to suggestions on
improving this.
This commit is contained in:
Karl Seguin
2025-12-18 20:10:38 +08:00
parent aa5e71112e
commit b3a0aaaeea
17 changed files with 693 additions and 409 deletions
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4
src/main.zig
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@@ -100,7 +100,7 @@ fn run(allocator: Allocator, main_arena: Allocator) !void {
switch (args.mode) {
.serve => |opts| {
log.debug(.app, "startup", .{ .mode = "serve" });
log.debug(.app, "startup", .{ .mode = "serve", .snapshot = app.snapshot.fromEmbedded() });
const address = std.net.Address.parseIp(opts.host, opts.port) catch |err| {
log.fatal(.app, "invalid server address", .{ .err = err, .host = opts.host, .port = opts.port });
return args.printUsageAndExit(false);
@@ -120,7 +120,7 @@ fn run(allocator: Allocator, main_arena: Allocator) !void {
},
.fetch => |opts| {
const url = opts.url;
log.debug(.app, "startup", .{ .mode = "fetch", .dump = opts.dump, .url = url });
log.debug(.app, "startup", .{ .mode = "fetch", .dump = opts.dump, .url = url, .snapshot = app.snapshot.fromEmbedded() });
var fetch_opts = lp.FetchOpts{
.wait_ms = 5000,