From 4e8edafb398f52499f9e975ffb8765cdbd268f34 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bartek=20Iwa=C5=84czuk?= Date: Wed, 8 Mar 2023 23:42:46 -0400 Subject: perf(core): over-allocate in ModuleMap when running from snapshot (#18083) This commit changes "ModuleMap" initialization to over-allocate by 16 for vectors storing module information and module V8 handles. In 99% cases there's gonna be at least one additional module loaded, so it's very wasteful to have to reallocate when the module is executed (IIRC Rust will double the size of the vector) and move all of the elements. --- core/runtime.rs | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'core/runtime.rs') diff --git a/core/runtime.rs b/core/runtime.rs index 456dbe828..b9da06346 100644 --- a/core/runtime.rs +++ b/core/runtime.rs @@ -463,7 +463,6 @@ impl JsRuntime { } } - let mut module_handles = vec![]; let mut scope = v8::ContextScope::new(scope, context); // The 0th element is the module map itself, followed by X number of module // handles. We need to deserialize the "next_module_id" field from the @@ -476,6 +475,9 @@ impl JsRuntime { info_data.length() }; + // Over allocate so executing a few scripts doesn't have to resize this vec. + let mut module_handles = + Vec::with_capacity(next_module_id as usize + 16); for i in 1..=next_module_id { match scope .get_context_data_from_snapshot_once::(i as usize) -- cgit v1.2.3