bjoernager/rust
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Auto merge of #83214 - cjgillot:dep-map, r=michaelwoerister

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Mmap the incremental data instead of reading it.

Instead of reading the full incremental state using `fs::read_file`, we memmap it using a private read-only file-backed map.
This allows the system to reclaim any memory we are not using, while ensuring we are not polluted by
outside modifications to the file.

Suggested in https://github.com/rust-lang/rust/pull/83036#issuecomment-800458082 by `@bjorn3`
This commit is contained in:
bors 2021-09-06 23:58:16 +00:00
commit 11bbb52313
5 changed files with 123 additions and 88 deletions
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58
compiler/rustc_query_impl/src/on_disk_cache.rs
View file

@ -1,6 +1,7 @@
use crate::QueryCtxt;
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
use rustc_data_structures::sync::{HashMapExt, Lock, Lrc, OnceCell};
use rustc_data_structures::memmap::Mmap;
use rustc_data_structures::sync::{HashMapExt, Lock, Lrc, OnceCell, RwLock};
use rustc_data_structures::unhash::UnhashMap;
use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, StableCrateId, LOCAL_CRATE};
use rustc_hir::definitions::DefPathHash;
@ -42,7 +43,7 @@ const TAG_EXPN_DATA: u8 = 1;
/// any side effects that have been emitted during a query.
pub struct OnDiskCache<'sess> {
// The complete cache data in serialized form.
serialized_data: Vec<u8>,
serialized_data: RwLock<Option<Mmap>>,
// Collects all `QuerySideEffects` created during the current compilation
// session.
@ -182,7 +183,8 @@ impl EncodedSourceFileId {
}
impl<'sess> rustc_middle::ty::OnDiskCache<'sess> for OnDiskCache<'sess> {
fn new(sess: &'sess Session, data: Vec<u8>, start_pos: usize) -> Self {
/// Creates a new `OnDiskCache` instance from the serialized data in `data`.
fn new(sess: &'sess Session, data: Mmap, start_pos: usize) -> Self {
debug_assert!(sess.opts.incremental.is_some());
// Wrap in a scope so we can borrow `data`.
@ -204,7 +206,7 @@ impl<'sess> rustc_middle::ty::OnDiskCache<'sess> for OnDiskCache<'sess> {
};
Self {
serialized_data: data,
serialized_data: RwLock::new(Some(data)),
file_index_to_stable_id: footer.file_index_to_stable_id,
file_index_to_file: Default::default(),
cnum_map: OnceCell::new(),
@ -225,7 +227,7 @@ impl<'sess> rustc_middle::ty::OnDiskCache<'sess> for OnDiskCache<'sess> {
fn new_empty(source_map: &'sess SourceMap) -> Self {
Self {
serialized_data: Vec::new(),
serialized_data: RwLock::new(None),
file_index_to_stable_id: Default::default(),
file_index_to_file: Default::default(),
cnum_map: OnceCell::new(),
@ -244,7 +246,31 @@ impl<'sess> rustc_middle::ty::OnDiskCache<'sess> for OnDiskCache<'sess> {
}
}
fn serialize(&self, tcx: TyCtxt<'sess>, encoder: &mut FileEncoder) -> FileEncodeResult {
/// Execute all cache promotions and release the serialized backing Mmap.
///
/// Cache promotions require invoking queries, which needs to read the serialized data.
/// In order to serialize the new on-disk cache, the former on-disk cache file needs to be
/// deleted, hence we won't be able to refer to its memmapped data.
fn drop_serialized_data(&self, tcx: TyCtxt<'tcx>) {
// Register any dep nodes that we reused from the previous session,
// but didn't `DepNode::construct` in this session. This ensures
// that their `DefPathHash` to `RawDefId` mappings are registered
// in 'latest_foreign_def_path_hashes' if necessary, since that
// normally happens in `DepNode::construct`.
tcx.dep_graph.register_reused_dep_nodes(tcx);
// Load everything into memory so we can write it out to the on-disk
// cache. The vast majority of cacheable query results should already
// be in memory, so this should be a cheap operation.
// Do this *before* we clone 'latest_foreign_def_path_hashes', since
// loading existing queries may cause us to create new DepNodes, which
// may in turn end up invoking `store_foreign_def_id_hash`
tcx.dep_graph.exec_cache_promotions(QueryCtxt::from_tcx(tcx));
*self.serialized_data.write() = None;
}
fn serialize<'tcx>(&self, tcx: TyCtxt<'tcx>, encoder: &mut FileEncoder) -> FileEncodeResult {
// Serializing the `DepGraph` should not modify it.
tcx.dep_graph.with_ignore(|| {
// Allocate `SourceFileIndex`es.
@ -266,21 +292,6 @@ impl<'sess> rustc_middle::ty::OnDiskCache<'sess> for OnDiskCache<'sess> {
(file_to_file_index, file_index_to_stable_id)
};
// Register any dep nodes that we reused from the previous session,
// but didn't `DepNode::construct` in this session. This ensures
// that their `DefPathHash` to `RawDefId` mappings are registered
// in 'latest_foreign_def_path_hashes' if necessary, since that
// normally happens in `DepNode::construct`.
tcx.dep_graph.register_reused_dep_nodes(tcx);
// Load everything into memory so we can write it out to the on-disk
// cache. The vast majority of cacheable query results should already
// be in memory, so this should be a cheap operation.
// Do this *before* we clone 'latest_foreign_def_path_hashes', since
// loading existing queries may cause us to create new DepNodes, which
// may in turn end up invoking `store_foreign_def_id_hash`
tcx.dep_graph.exec_cache_promotions(QueryCtxt::from_tcx(tcx));
let latest_foreign_def_path_hashes = self.latest_foreign_def_path_hashes.lock().clone();
let hygiene_encode_context = HygieneEncodeContext::default();
@ -564,7 +575,7 @@ impl<'sess> OnDiskCache<'sess> {
})
}
fn with_decoder<'a, 'tcx, T, F: FnOnce(&mut CacheDecoder<'sess, 'tcx>) -> T>(
fn with_decoder<'a, 'tcx, T, F: for<'s> FnOnce(&mut CacheDecoder<'s, 'tcx>) -> T>(
&'sess self,
tcx: TyCtxt<'tcx>,
pos: AbsoluteBytePos,
@ -575,9 +586,10 @@ impl<'sess> OnDiskCache<'sess> {
{
let cnum_map = self.cnum_map.get_or_init(|| Self::compute_cnum_map(tcx));
let serialized_data = self.serialized_data.read();
let mut decoder = CacheDecoder {
tcx,
opaque: opaque::Decoder::new(&self.serialized_data[..], pos.to_usize()),
opaque: opaque::Decoder::new(serialized_data.as_deref().unwrap_or(&[]), pos.to_usize()),
source_map: self.source_map,
cnum_map,
file_index_to_file: &self.file_index_to_file,