Commit 47a55832 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r368498: 

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r368498 | sammccall | 2019-08-10 01:03:32 +0200 (Sat, 10 Aug 2019) | 25 lines

clangd: use -j for background index pool

Summary:
clangd supports a -j option to limit the amount of threads to use for parsing
TUs. However, when using -background-index (the default in later versions of
clangd), the parallelism used by clangd defaults to the hardware_parallelisn,
i.e. number of physical cores.

On shared hardware environments, with large projects, this can significantly
affect performance with no way to tune it down.

This change makes the -j parameter apply equally to parsing and background
index. It's not perfect, because the total number of threads is 2x the -j value,
which may still be unexpected. But at least this change allows users to prevent
clangd using all CPU cores.

Reviewers: kadircet, sammccall

Reviewed By: sammccall

Subscribers: javed.absar, jfb, sammccall, ilya-biryukov, MaskRay, jkorous, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D66031
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llvm-svn: 368569
parent a23c9071

clang-tools-extra/clangd/ClangdServer.cpp

+5 −3
Original line number Diff line number Diff line
@@ -38,9 +38,11 @@ 
#include "llvm/Support/FileSystem.h"

#include "llvm/Support/Path.h"

#include "llvm/Support/raw_ostream.h"

#include <algorithm>

#include <future>

#include <memory>

#include <mutex>

#include <type_traits>



namespace clang {

namespace clangd {
@@ -101,8 +103,7 @@ ClangdServer::ClangdServer(const GlobalCompilationDatabase &CDB, 
                     : nullptr),

      GetClangTidyOptions(Opts.GetClangTidyOptions),

      SuggestMissingIncludes(Opts.SuggestMissingIncludes),

      TweakFilter(Opts.TweakFilter),

      WorkspaceRoot(Opts.WorkspaceRoot),

      TweakFilter(Opts.TweakFilter), WorkspaceRoot(Opts.WorkspaceRoot),

      // Pass a callback into `WorkScheduler` to extract symbols from a newly

      // parsed file and rebuild the file index synchronously each time an AST

      // is parsed.
@@ -128,7 +129,8 @@ ClangdServer::ClangdServer(const GlobalCompilationDatabase &CDB, 
    BackgroundIdx = llvm::make_unique<BackgroundIndex>(

        Context::current().clone(), FSProvider, CDB,

        BackgroundIndexStorage::createDiskBackedStorageFactory(

            [&CDB](llvm::StringRef File) { return CDB.getProjectInfo(File); }));

            [&CDB](llvm::StringRef File) { return CDB.getProjectInfo(File); }),

        std::max(Opts.AsyncThreadsCount, 1u));

    AddIndex(BackgroundIdx.get());

  }

  if (DynamicIdx)

clang-tools-extra/clangd/TUScheduler.cpp

+5 −4
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ 
#include "llvm/ADT/ScopeExit.h"

#include "llvm/Support/Errc.h"

#include "llvm/Support/Path.h"

#include "llvm/Support/Threading.h"

#include <algorithm>

#include <memory>

#include <queue>
@@ -799,10 +800,10 @@ std::string renderTUAction(const TUAction &Action) { 
} // namespace



unsigned getDefaultAsyncThreadsCount() {

  unsigned HardwareConcurrency = std::thread::hardware_concurrency();

  // C++ standard says that hardware_concurrency()

  // may return 0, fallback to 1 worker thread in

  // that case.

  unsigned HardwareConcurrency = llvm::heavyweight_hardware_concurrency();

  // heavyweight_hardware_concurrency may fall back to hardware_concurrency.

  // C++ standard says that hardware_concurrency() may return 0; fallback to 1

  // worker thread in that case.

  if (HardwareConcurrency == 0)

    return 1;

  return HardwareConcurrency;

clang-tools-extra/clangd/tool/ClangdMain.cpp

+4 −2
Original line number Diff line number Diff line
@@ -267,7 +267,8 @@ list<std::string> TweakList{ 
opt<unsigned> WorkerThreadsCount{

    "j",

    cat(Misc),

    desc("Number of async workers used by clangd"),

    desc("Number of async workers used by clangd. Background index also "

         "uses this many workers."),

    init(getDefaultAsyncThreadsCount()),

};
@@ -308,7 +309,8 @@ opt<PCHStorageFlag> PCHStorage{ 
opt<bool> Sync{

    "sync",

    cat(Misc),

    desc("Parse on main thread. If set, -j is ignored"),

    desc("Handle client requests on main thread. Background index still uses "

         "its own thread."),

    init(false),

    Hidden,

};