forked from OSchip/llvm-project
102 lines
3.8 KiB
C++
102 lines
3.8 KiB
C++
//===--- BackgroundIndexRebuild.h - when to rebuild the bg index--*- C++-*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains an implementation detail of the background indexer
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// (Background.h), which is exposed for testing.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_BACKGROUNDREBUILD_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_BACKGROUNDREBUILD_H
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#include "index/FileIndex.h"
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#include "index/Index.h"
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#include <cstddef>
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namespace clang {
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namespace clangd {
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// The BackgroundIndexRebuilder builds the serving data structures periodically
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// in response to events in the background indexer. The goal is to ensure the
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// served data stays fairly fresh, without wasting lots of CPU rebuilding it
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// often.
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//
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// The index is always built after a set of shards are loaded from disk.
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// This happens when clangd discovers a compilation database that we've
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// previously built an index for. It's a fairly fast process that yields lots
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// of data, so we wait to get all of it.
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//
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// The index is built after indexing a few translation units, if it wasn't built
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// already. This ensures quick startup if there's no existing index.
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// Waiting for a few random TUs yields coverage of the most common headers.
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//
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// The index is rebuilt every N TUs, to keep if fresh as files are indexed.
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//
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// The index is rebuilt every time the queue goes idle, if it's stale.
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//
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// All methods are threadsafe. They're called after FileSymbols is updated
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// etc. Without external locking, the rebuilt index may include more updates
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// than intended, which is fine.
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//
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// This class is exposed in the header so it can be tested.
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class BackgroundIndexRebuilder {
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public:
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BackgroundIndexRebuilder(SwapIndex *Target, FileSymbols *Source,
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unsigned Threads)
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: TUsBeforeFirstBuild(Threads), Target(Target), Source(Source) {}
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// Called to indicate a TU has been indexed.
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// May rebuild, if enough TUs have been indexed.
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void indexedTU();
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// Called to indicate that all worker threads are idle.
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// May reindex, if the index is not up to date.
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void idle();
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// Called to indicate we're going to load a batch of shards from disk.
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// startLoading() and doneLoading() must be paired, but multiple loading
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// sessions may happen concurrently.
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void startLoading();
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// Called to indicate some shards were actually loaded from disk.
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void loadedShard(size_t ShardCount);
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// Called to indicate we're finished loading shards from disk.
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// May rebuild (if any were loaded).
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void doneLoading();
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// Ensures we won't start any more rebuilds.
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void shutdown();
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// Thresholds for rebuilding as TUs get indexed. Exposed for testing.
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const unsigned TUsBeforeFirstBuild; // Typically one per worker thread.
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const unsigned TUsBeforeRebuild = 100;
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private:
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// Run Check under the lock, and rebuild if it returns true.
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void maybeRebuild(const char *Reason, std::function<bool()> Check);
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bool enoughTUsToRebuild() const;
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// All transient state is guarded by the mutex.
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std::mutex Mu;
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bool ShouldStop = false;
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// Index builds are versioned. ActiveVersion chases StartedVersion.
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unsigned StartedVersion = 0;
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unsigned ActiveVersion = 0;
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// How many TUs have we indexed so far since startup?
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unsigned IndexedTUs = 0;
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unsigned IndexedTUsAtLastRebuild = 0;
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// Are we loading shards? May be multiple concurrent sessions.
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unsigned Loading = 0;
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unsigned LoadedShards; // In the current loading session.
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SwapIndex *Target;
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FileSymbols *Source;
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};
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} // namespace clangd
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} // namespace clang
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#endif
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