diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 013433336a1..20d4c417655 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -10,7 +10,6 @@
 
 //! Support for inlining external documentation into the current AST.
 
-use std::collections::HashSet;
 use std::iter::once;
 
 use syntax::ast;
@@ -21,6 +20,7 @@ use rustc::hir::def::Def;
 use rustc::hir::def_id::DefId;
 use rustc::hir::print as pprust;
 use rustc::ty::{self, TyCtxt};
+use rustc::util::nodemap::FnvHashSet;
 
 use rustc_const_eval::lookup_const_by_id;
 
@@ -425,7 +425,7 @@ pub fn build_impl<'a, 'tcx>(cx: &DocContext,
                 .into_iter()
                 .map(|meth| meth.name.to_string())
                 .collect()
-    }).unwrap_or(HashSet::new());
+    }).unwrap_or(FnvHashSet());
 
     ret.push(clean::Item {
         inner: clean::ImplItem(clean::Impl {
@@ -461,7 +461,7 @@ fn build_module<'a, 'tcx>(cx: &DocContext, tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // If we're reexporting a reexport it may actually reexport something in
         // two namespaces, so the target may be listed twice. Make sure we only
         // visit each node at most once.
-        let mut visited = HashSet::new();
+        let mut visited = FnvHashSet();
         for item in tcx.sess.cstore.item_children(did) {
             match item.def {
                 cstore::DlDef(Def::ForeignMod(did)) => {
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index c8620254b6f..cd425b7c9eb 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -43,10 +43,10 @@ use rustc::hir::print as pprust;
 use rustc::ty::subst::Substs;
 use rustc::ty;
 use rustc::middle::stability;
+use rustc::util::nodemap::{FnvHashMap, FnvHashSet};
 
 use rustc::hir;
 
-use std::collections::{HashMap, HashSet};
 use std::path::PathBuf;
 use std::rc::Rc;
 use std::sync::Arc;
@@ -121,7 +121,7 @@ pub struct Crate {
     pub access_levels: Arc<AccessLevels<DefId>>,
     // These are later on moved into `CACHEKEY`, leaving the map empty.
     // Only here so that they can be filtered through the rustdoc passes.
-    pub external_traits: HashMap<DefId, Trait>,
+    pub external_traits: FnvHashMap<DefId, Trait>,
 }
 
 struct CrateNum(ast::CrateNum);
@@ -1010,7 +1010,7 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics<'tcx>,
         // Note that associated types also have a sized bound by default, but we
         // don't actually know the set of associated types right here so that's
         // handled in cleaning associated types
-        let mut sized_params = HashSet::new();
+        let mut sized_params = FnvHashSet();
         where_predicates.retain(|pred| {
             match *pred {
                 WP::BoundPredicate { ty: Generic(ref g), ref bounds } => {
@@ -1656,9 +1656,9 @@ impl From<ast::FloatTy> for PrimitiveType {
 struct SubstAlias<'a, 'tcx: 'a> {
     tcx: &'a ty::TyCtxt<'a, 'tcx, 'tcx>,
     // Table type parameter definition -> substituted type
-    ty_substs: HashMap<Def, hir::Ty>,
+    ty_substs: FnvHashMap<Def, hir::Ty>,
     // Table node id of lifetime parameter definition -> substituted lifetime
-    lt_substs: HashMap<ast::NodeId, hir::Lifetime>,
+    lt_substs: FnvHashMap<ast::NodeId, hir::Lifetime>,
 }
 
 impl<'a, 'tcx: 'a, 'b: 'tcx> Folder for SubstAlias<'a, 'tcx> {
@@ -1727,8 +1727,8 @@ impl Clean<Type> for hir::Ty {
                                 let item = tcx.map.expect_item(node_id);
                                 if let hir::ItemTy(ref ty, ref generics) = item.node {
                                     let provided_params = &path.segments.last().unwrap().parameters;
-                                    let mut ty_substs = HashMap::new();
-                                    let mut lt_substs = HashMap::new();
+                                    let mut ty_substs = FnvHashMap();
+                                    let mut lt_substs = FnvHashMap();
                                     for (i, ty_param) in generics.ty_params.iter().enumerate() {
                                         let ty_param_def = tcx.expect_def(ty_param.id);
                                         if let Some(ty) = provided_params.types().get(i).cloned()
@@ -2384,7 +2384,7 @@ impl Clean<ImplPolarity> for hir::ImplPolarity {
 pub struct Impl {
     pub unsafety: hir::Unsafety,
     pub generics: Generics,
-    pub provided_trait_methods: HashSet<String>,
+    pub provided_trait_methods: FnvHashSet<String>,
     pub trait_: Option<Type>,
     pub for_: Type,
     pub items: Vec<Item>,
@@ -2410,7 +2410,7 @@ impl Clean<Vec<Item>> for doctree::Impl {
                    .map(|meth| meth.name.to_string())
                    .collect()
             })
-        }).unwrap_or(HashSet::new());
+        }).unwrap_or(FnvHashSet());
 
         ret.push(Item {
             name: None,
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 8032b5c3104..26f792a1fdf 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -18,6 +18,7 @@ use rustc::middle::privacy::AccessLevels;
 use rustc::ty::{self, TyCtxt};
 use rustc::hir::map as hir_map;
 use rustc::lint;
+use rustc::util::nodemap::{FnvHashMap, FnvHashSet};
 use rustc_trans::back::link;
 use rustc_resolve as resolve;
 use rustc_metadata::cstore::CStore;
@@ -28,7 +29,6 @@ use errors;
 use errors::emitter::ColorConfig;
 
 use std::cell::{RefCell, Cell};
-use std::collections::{HashMap, HashSet};
 use std::rc::Rc;
 
 use visit_ast::RustdocVisitor;
@@ -45,13 +45,13 @@ pub enum MaybeTyped<'a, 'tcx: 'a> {
     NotTyped(&'a session::Session)
 }
 
-pub type ExternalPaths = HashMap<DefId, (Vec<String>, clean::TypeKind)>;
+pub type ExternalPaths = FnvHashMap<DefId, (Vec<String>, clean::TypeKind)>;
 
 pub struct DocContext<'a, 'tcx: 'a> {
     pub map: &'a hir_map::Map<'tcx>,
     pub maybe_typed: MaybeTyped<'a, 'tcx>,
     pub input: Input,
-    pub populated_crate_impls: RefCell<HashSet<ast::CrateNum>>,
+    pub populated_crate_impls: RefCell<FnvHashSet<ast::CrateNum>>,
     pub deref_trait_did: Cell<Option<DefId>>,
     // Note that external items for which `doc(hidden)` applies to are shown as
     // non-reachable while local items aren't. This is because we're reusing
@@ -61,7 +61,7 @@ pub struct DocContext<'a, 'tcx: 'a> {
     /// Later on moved into `html::render::CACHE_KEY`
     pub renderinfo: RefCell<RenderInfo>,
     /// Later on moved through `clean::Crate` into `html::render::CACHE_KEY`
-    pub external_traits: RefCell<HashMap<DefId, clean::Trait>>,
+    pub external_traits: RefCell<FnvHashMap<DefId, clean::Trait>>,
 }
 
 impl<'b, 'tcx> DocContext<'b, 'tcx> {
@@ -178,10 +178,10 @@ pub fn run_core(search_paths: SearchPaths,
             map: &tcx.map,
             maybe_typed: Typed(tcx),
             input: input,
-            populated_crate_impls: RefCell::new(HashSet::new()),
+            populated_crate_impls: RefCell::new(FnvHashSet()),
             deref_trait_did: Cell::new(None),
             access_levels: RefCell::new(access_levels),
-            external_traits: RefCell::new(HashMap::new()),
+            external_traits: RefCell::new(FnvHashMap()),
             renderinfo: RefCell::new(Default::default()),
         };
         debug!("crate: {:?}", ctxt.map.krate());
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 6993f85c3d9..5cb5cc05187 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -37,7 +37,7 @@ pub use self::ExternalLocation::*;
 use std::ascii::AsciiExt;
 use std::cell::RefCell;
 use std::cmp::Ordering;
-use std::collections::{BTreeMap, HashMap, HashSet};
+use std::collections::BTreeMap;
 use std::default::Default;
 use std::error;
 use std::fmt::{self, Display, Formatter};
@@ -61,6 +61,7 @@ use rustc::middle::privacy::AccessLevels;
 use rustc::middle::stability;
 use rustc::session::config::get_unstable_features_setting;
 use rustc::hir;
+use rustc::util::nodemap::{FnvHashMap, FnvHashSet};
 
 use clean::{self, Attributes, GetDefId};
 use doctree;
@@ -114,9 +115,9 @@ pub struct SharedContext {
     /// `true`.
     pub include_sources: bool,
     /// The local file sources we've emitted and their respective url-paths.
-    pub local_sources: HashMap<PathBuf, String>,
+    pub local_sources: FnvHashMap<PathBuf, String>,
     /// All the passes that were run on this crate.
-    pub passes: HashSet<String>,
+    pub passes: FnvHashSet<String>,
     /// The base-URL of the issue tracker for when an item has been tagged with
     /// an issue number.
     pub issue_tracker_base_url: Option<String>,
@@ -211,7 +212,7 @@ pub struct Cache {
     /// Mapping of typaram ids to the name of the type parameter. This is used
     /// when pretty-printing a type (so pretty printing doesn't have to
     /// painfully maintain a context like this)
-    pub typarams: HashMap<DefId, String>,
+    pub typarams: FnvHashMap<DefId, String>,
 
     /// Maps a type id to all known implementations for that type. This is only
     /// recognized for intra-crate `ResolvedPath` types, and is used to print
@@ -219,35 +220,35 @@ pub struct Cache {
     ///
     /// The values of the map are a list of implementations and documentation
     /// found on that implementation.
-    pub impls: HashMap<DefId, Vec<Impl>>,
+    pub impls: FnvHashMap<DefId, Vec<Impl>>,
 
     /// Maintains a mapping of local crate node ids to the fully qualified name
     /// and "short type description" of that node. This is used when generating
     /// URLs when a type is being linked to. External paths are not located in
     /// this map because the `External` type itself has all the information
     /// necessary.
-    pub paths: HashMap<DefId, (Vec<String>, ItemType)>,
+    pub paths: FnvHashMap<DefId, (Vec<String>, ItemType)>,
 
     /// Similar to `paths`, but only holds external paths. This is only used for
     /// generating explicit hyperlinks to other crates.
-    pub external_paths: HashMap<DefId, (Vec<String>, ItemType)>,
+    pub external_paths: FnvHashMap<DefId, (Vec<String>, ItemType)>,
 
     /// This map contains information about all known traits of this crate.
     /// Implementations of a crate should inherit the documentation of the
     /// parent trait if no extra documentation is specified, and default methods
     /// should show up in documentation about trait implementations.
-    pub traits: HashMap<DefId, clean::Trait>,
+    pub traits: FnvHashMap<DefId, clean::Trait>,
 
     /// When rendering traits, it's often useful to be able to list all
     /// implementors of the trait, and this mapping is exactly, that: a mapping
     /// of trait ids to the list of known implementors of the trait
-    pub implementors: HashMap<DefId, Vec<Implementor>>,
+    pub implementors: FnvHashMap<DefId, Vec<Implementor>>,
 
     /// Cache of where external crate documentation can be found.
-    pub extern_locations: HashMap<ast::CrateNum, (String, ExternalLocation)>,
+    pub extern_locations: FnvHashMap<ast::CrateNum, (String, ExternalLocation)>,
 
     /// Cache of where documentation for primitives can be found.
-    pub primitive_locations: HashMap<clean::PrimitiveType, ast::CrateNum>,
+    pub primitive_locations: FnvHashMap<clean::PrimitiveType, ast::CrateNum>,
 
     // Note that external items for which `doc(hidden)` applies to are shown as
     // non-reachable while local items aren't. This is because we're reusing
@@ -260,7 +261,7 @@ pub struct Cache {
     parent_stack: Vec<DefId>,
     parent_is_trait_impl: bool,
     search_index: Vec<IndexItem>,
-    seen_modules: HashSet<DefId>,
+    seen_modules: FnvHashSet<DefId>,
     seen_mod: bool,
     stripped_mod: bool,
     deref_trait_did: Option<DefId>,
@@ -277,9 +278,9 @@ pub struct Cache {
 /// Later on moved into `CACHE_KEY`.
 #[derive(Default)]
 pub struct RenderInfo {
-    pub inlined: HashSet<DefId>,
+    pub inlined: FnvHashSet<DefId>,
     pub external_paths: ::core::ExternalPaths,
-    pub external_typarams: HashMap<DefId, String>,
+    pub external_typarams: FnvHashMap<DefId, String>,
     pub deref_trait_did: Option<DefId>,
 }
 
@@ -377,10 +378,10 @@ impl ToJson for IndexItemFunctionType {
 thread_local!(static CACHE_KEY: RefCell<Arc<Cache>> = Default::default());
 thread_local!(pub static CURRENT_LOCATION_KEY: RefCell<Vec<String>> =
                     RefCell::new(Vec::new()));
-thread_local!(static USED_ID_MAP: RefCell<HashMap<String, usize>> =
+thread_local!(static USED_ID_MAP: RefCell<FnvHashMap<String, usize>> =
                     RefCell::new(init_ids()));
 
-fn init_ids() -> HashMap<String, usize> {
+fn init_ids() -> FnvHashMap<String, usize> {
     [
      "main",
      "search",
@@ -407,7 +408,7 @@ pub fn reset_ids(embedded: bool) {
         *s.borrow_mut() = if embedded {
             init_ids()
         } else {
-            HashMap::new()
+            FnvHashMap()
         };
     });
 }
@@ -432,7 +433,7 @@ pub fn derive_id(candidate: String) -> String {
 pub fn run(mut krate: clean::Crate,
            external_html: &ExternalHtml,
            dst: PathBuf,
-           passes: HashSet<String>,
+           passes: FnvHashSet<String>,
            css_file_extension: Option<PathBuf>,
            renderinfo: RenderInfo) -> Result<(), Error> {
     let src_root = match krate.src.parent() {
@@ -443,7 +444,7 @@ pub fn run(mut krate: clean::Crate,
         src_root: src_root,
         passes: passes,
         include_sources: true,
-        local_sources: HashMap::new(),
+        local_sources: FnvHashMap(),
         issue_tracker_base_url: None,
         layout: layout::Layout {
             logo: "".to_string(),
@@ -513,22 +514,22 @@ pub fn run(mut krate: clean::Crate,
         .collect();
 
     let mut cache = Cache {
-        impls: HashMap::new(),
+        impls: FnvHashMap(),
         external_paths: external_paths,
-        paths: HashMap::new(),
-        implementors: HashMap::new(),
+        paths: FnvHashMap(),
+        implementors: FnvHashMap(),
         stack: Vec::new(),
         parent_stack: Vec::new(),
         search_index: Vec::new(),
         parent_is_trait_impl: false,
-        extern_locations: HashMap::new(),
-        primitive_locations: HashMap::new(),
-        seen_modules: HashSet::new(),
+        extern_locations: FnvHashMap(),
+        primitive_locations: FnvHashMap(),
+        seen_modules: FnvHashSet(),
         seen_mod: false,
         stripped_mod: false,
         access_levels: krate.access_levels.clone(),
         orphan_methods: Vec::new(),
-        traits: mem::replace(&mut krate.external_traits, HashMap::new()),
+        traits: mem::replace(&mut krate.external_traits, FnvHashMap()),
         deref_trait_did: deref_trait_did,
         typarams: external_typarams,
     };
@@ -574,7 +575,7 @@ pub fn run(mut krate: clean::Crate,
 
 /// Build the search index from the collected metadata
 fn build_index(krate: &clean::Crate, cache: &mut Cache) -> String {
-    let mut nodeid_to_pathid = HashMap::new();
+    let mut nodeid_to_pathid = FnvHashMap();
     let mut crate_items = Vec::with_capacity(cache.search_index.len());
     let mut crate_paths = Vec::<Json>::new();
 
@@ -2515,7 +2516,7 @@ fn render_struct(w: &mut fmt::Formatter, it: &clean::Item,
 #[derive(Copy, Clone)]
 enum AssocItemLink<'a> {
     Anchor(Option<&'a str>),
-    GotoSource(DefId, &'a HashSet<String>),
+    GotoSource(DefId, &'a FnvHashSet<String>),
 }
 
 impl<'a> AssocItemLink<'a> {
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 7d1dbbe5dc0..e7edf8d1cab 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -9,7 +9,6 @@
 // except according to those terms.
 
 use std::cell::{RefCell, Cell};
-use std::collections::{HashMap, HashSet};
 use std::env;
 use std::ffi::OsString;
 use std::io::prelude::*;
@@ -29,6 +28,7 @@ use rustc::session::{self, config};
 use rustc::session::config::{get_unstable_features_setting, OutputType,
                              OutputTypes, Externs};
 use rustc::session::search_paths::{SearchPaths, PathKind};
+use rustc::util::nodemap::{FnvHashMap, FnvHashSet};
 use rustc_back::dynamic_lib::DynamicLibrary;
 use rustc_back::tempdir::TempDir;
 use rustc_driver::{driver, Compilation};
@@ -107,8 +107,8 @@ pub fn run(input: &str,
         map: &map,
         maybe_typed: core::NotTyped(&sess),
         input: input,
-        external_traits: RefCell::new(HashMap::new()),
-        populated_crate_impls: RefCell::new(HashSet::new()),
+        external_traits: RefCell::new(FnvHashMap()),
+        populated_crate_impls: RefCell::new(FnvHashSet()),
         deref_trait_did: Cell::new(None),
         access_levels: Default::default(),
         renderinfo: Default::default(),
diff --git a/src/librustdoc/visit_ast.rs b/src/librustdoc/visit_ast.rs
index 0334c5ef5c4..f6084180f0b 100644
--- a/src/librustdoc/visit_ast.rs
+++ b/src/librustdoc/visit_ast.rs
@@ -11,7 +11,6 @@
 //! Rust AST Visitor. Extracts useful information and massages it into a form
 //! usable for clean
 
-use std::collections::HashSet;
 use std::mem;
 
 use syntax::abi;
@@ -23,6 +22,7 @@ use syntax_pos::Span;
 use rustc::hir::map as hir_map;
 use rustc::hir::def::Def;
 use rustc::middle::privacy::AccessLevel;
+use rustc::util::nodemap::FnvHashSet;
 
 use rustc::hir;
 
@@ -42,14 +42,14 @@ pub struct RustdocVisitor<'a, 'tcx: 'a> {
     pub module: Module,
     pub attrs: hir::HirVec<ast::Attribute>,
     pub cx: &'a core::DocContext<'a, 'tcx>,
-    view_item_stack: HashSet<ast::NodeId>,
+    view_item_stack: FnvHashSet<ast::NodeId>,
     inlining_from_glob: bool,
 }
 
 impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
     pub fn new(cx: &'a core::DocContext<'a, 'tcx>) -> RustdocVisitor<'a, 'tcx> {
         // If the root is reexported, terminate all recursion.
-        let mut stack = HashSet::new();
+        let mut stack = FnvHashSet();
         stack.insert(ast::CRATE_NODE_ID);
         RustdocVisitor {
             module: Module::new(None),