[compiler-rt] r314766 - [XRay][compiler-rt] Use a hand-written circular buffer in BufferQueue
Diana Picus via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 3 02:10:16 PDT 2017
Hi,
Looks like this broke a number of bots:
http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15-full/builds/11102
http://lab.llvm.org:8011/builders/clang-ppc64le-linux-lnt/builds/7016/
http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-debian-fast/builds/6251
Are you looking into it?
Thanks,
Diana
On 3 October 2017 at 08:15, Dean Michael Berris via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: dberris
> Date: Mon Oct 2 23:15:34 2017
> New Revision: 314766
>
> URL: http://llvm.org/viewvc/llvm-project?rev=314766&view=rev
> Log:
> [XRay][compiler-rt] Use a hand-written circular buffer in BufferQueue
>
> Summary:
> This change removes the dependency on using a std::deque<...> for the
> storage of the buffers in the buffer queue. We instead implement a
> fixed-size circular buffer that's resilient to exhaustion, and preserves
> the semantics of the BufferQueue.
>
> We're moving away from using std::deque<...> for two reasons:
>
> - We want to remove dependencies on the STL for data structures.
>
> - We want the data structure we use to not require re-allocation in
> the normal course of operation.
>
> The internal implementation of the buffer queue uses heap-allocated
> arrays that are initialized once when the BufferQueue is created, and
> re-uses slots in the buffer array as buffers are returned in order.
>
> We also change the lock used in the implementation to a spinlock
> instead of a blocking mutex. We reason that since the release operations
> now take very little time in the critical section, that a spinlock would
> be appropriate.
>
> This change is related to D38073.
>
> Reviewers: dblaikie, kpw, pelikan
>
> Subscribers: llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D38119
>
> Modified:
> compiler-rt/trunk/lib/xray/xray_buffer_queue.cc
> compiler-rt/trunk/lib/xray/xray_buffer_queue.h
> compiler-rt/trunk/test/xray/TestCases/Linux/fdr-thread-order.cc
>
> Modified: compiler-rt/trunk/lib/xray/xray_buffer_queue.cc
> URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/xray/xray_buffer_queue.cc?rev=314766&r1=314765&r2=314766&view=diff
> ==============================================================================
> --- compiler-rt/trunk/lib/xray/xray_buffer_queue.cc (original)
> +++ compiler-rt/trunk/lib/xray/xray_buffer_queue.cc Mon Oct 2 23:15:34 2017
> @@ -16,6 +16,7 @@
> #include "sanitizer_common/sanitizer_common.h"
> #include "sanitizer_common/sanitizer_libc.h"
>
> +#include <algorithm>
> #include <cstdlib>
> #include <tuple>
>
> @@ -23,18 +24,21 @@ using namespace __xray;
> using namespace __sanitizer;
>
> BufferQueue::BufferQueue(std::size_t B, std::size_t N, bool &Success)
> - : BufferSize(B), Buffers(N), Mutex(), OwnedBuffers(), Finalizing{0} {
> - for (auto &T : Buffers) {
> + : BufferSize(B), Buffers(new std::tuple<Buffer, bool>[N]()),
> + BufferCount(N), Finalizing{0}, OwnedBuffers(new void *[N]()),
> + Next(Buffers.get()), First(nullptr) {
> + for (size_t i = 0; i < N; ++i) {
> + auto &T = Buffers[i];
> void *Tmp = malloc(BufferSize);
> if (Tmp == nullptr) {
> Success = false;
> return;
> }
> -
> auto &Buf = std::get<0>(T);
> + std::get<1>(T) = false;
> Buf.Buffer = Tmp;
> Buf.Size = B;
> - OwnedBuffers.emplace(Tmp);
> + OwnedBuffers[i] = Tmp;
> }
> Success = true;
> }
> @@ -42,27 +46,43 @@ BufferQueue::BufferQueue(std::size_t B,
> BufferQueue::ErrorCode BufferQueue::getBuffer(Buffer &Buf) {
> if (__sanitizer::atomic_load(&Finalizing, __sanitizer::memory_order_acquire))
> return ErrorCode::QueueFinalizing;
> - __sanitizer::BlockingMutexLock Guard(&Mutex);
> - if (Buffers.empty())
> + __sanitizer::SpinMutexLock Guard(&Mutex);
> +
> + if (Next == First)
> return ErrorCode::NotEnoughMemory;
> - auto &T = Buffers.front();
> +
> + auto &T = *Next;
> auto &B = std::get<0>(T);
> Buf = B;
> - B.Buffer = nullptr;
> - B.Size = 0;
> - Buffers.pop_front();
> +
> + if (First == nullptr)
> + First = Next;
> + ++Next;
> + if (Next == (Buffers.get() + BufferCount))
> + Next = Buffers.get();
> +
> return ErrorCode::Ok;
> }
>
> BufferQueue::ErrorCode BufferQueue::releaseBuffer(Buffer &Buf) {
> - if (OwnedBuffers.count(Buf.Buffer) == 0)
> + // Blitz through the buffers array to find the buffer.
> + if (std::none_of(OwnedBuffers.get(), OwnedBuffers.get() + BufferCount,
> + [&Buf](void *P) { return P == Buf.Buffer; }))
> return ErrorCode::UnrecognizedBuffer;
> - __sanitizer::BlockingMutexLock Guard(&Mutex);
> + __sanitizer::SpinMutexLock Guard(&Mutex);
> +
> + // This points to a semantic bug, we really ought to not be releasing more
> + // buffers than we actually get.
> + if (First == nullptr || First == Next)
> + return ErrorCode::NotEnoughMemory;
>
> // Now that the buffer has been released, we mark it as "used".
> - Buffers.emplace(Buffers.end(), Buf, true /* used */);
> + *First = std::make_tuple(Buf, true);
> Buf.Buffer = nullptr;
> Buf.Size = 0;
> + ++First;
> + if (First == (Buffers.get() + BufferCount))
> + First = Buffers.get();
> return ErrorCode::Ok;
> }
>
> @@ -74,7 +94,8 @@ BufferQueue::ErrorCode BufferQueue::fina
> }
>
> BufferQueue::~BufferQueue() {
> - for (auto &T : Buffers) {
> + for (auto I = Buffers.get(), E = Buffers.get() + BufferCount; I != E; ++I) {
> + auto &T = *I;
> auto &Buf = std::get<0>(T);
> free(Buf.Buffer);
> }
>
> Modified: compiler-rt/trunk/lib/xray/xray_buffer_queue.h
> URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/xray/xray_buffer_queue.h?rev=314766&r1=314765&r2=314766&view=diff
> ==============================================================================
> --- compiler-rt/trunk/lib/xray/xray_buffer_queue.h (original)
> +++ compiler-rt/trunk/lib/xray/xray_buffer_queue.h Mon Oct 2 23:15:34 2017
> @@ -17,8 +17,8 @@
>
> #include "sanitizer_common/sanitizer_atomic.h"
> #include "sanitizer_common/sanitizer_mutex.h"
> -#include <deque>
> -#include <unordered_set>
> +#include <cstdint>
> +#include <memory>
> #include <utility>
>
> namespace __xray {
> @@ -36,15 +36,23 @@ public:
> };
>
> private:
> + // Size of each individual Buffer.
> size_t BufferSize;
>
> // We use a bool to indicate whether the Buffer has been used in this
> // freelist implementation.
> - std::deque<std::tuple<Buffer, bool>> Buffers;
> - __sanitizer::BlockingMutex Mutex;
> - std::unordered_set<void *> OwnedBuffers;
> + std::unique_ptr<std::tuple<Buffer, bool>[]> Buffers;
> + size_t BufferCount;
> +
> + __sanitizer::SpinMutex Mutex;
> __sanitizer::atomic_uint8_t Finalizing;
>
> + // Sorted buffer pointers, making it quick to find buffers that we own.
> + std::unique_ptr<void *[]> OwnedBuffers;
> +
> + std::tuple<Buffer, bool> *Next;
> + std::tuple<Buffer, bool> *First;
> +
> public:
> enum class ErrorCode : unsigned {
> Ok,
> @@ -117,8 +125,9 @@ public:
> /// Buffer is marked 'used' (i.e. has been the result of getBuffer(...) and a
> /// releaseBuffer(...) operation).
> template <class F> void apply(F Fn) {
> - __sanitizer::BlockingMutexLock G(&Mutex);
> - for (const auto &T : Buffers) {
> + __sanitizer::SpinMutexLock G(&Mutex);
> + for (auto I = Buffers.get(), E = Buffers.get() + BufferCount; I != E; ++I) {
> + const auto &T = *I;
> if (std::get<1>(T))
> Fn(std::get<0>(T));
> }
>
> Modified: compiler-rt/trunk/test/xray/TestCases/Linux/fdr-thread-order.cc
> URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/xray/TestCases/Linux/fdr-thread-order.cc?rev=314766&r1=314765&r2=314766&view=diff
> ==============================================================================
> --- compiler-rt/trunk/test/xray/TestCases/Linux/fdr-thread-order.cc (original)
> +++ compiler-rt/trunk/test/xray/TestCases/Linux/fdr-thread-order.cc Mon Oct 2 23:15:34 2017
> @@ -1,37 +1,63 @@
> // RUN: %clangxx_xray -g -std=c++11 %s -o %t
> // RUN: rm fdr-thread-order.* || true
> -// RUN: XRAY_OPTIONS="patch_premain=false xray_naive_log=false xray_logfile_base=fdr-thread-order. xray_fdr_log=true verbosity=1 xray_fdr_log_func_duration_threshold_us=0" %run %t 2>&1 | FileCheck %s
> -// RUN: %llvm_xray convert --symbolize --output-format=yaml -instr_map=%t "`ls fdr-thread-order.* | head -1`" | FileCheck %s --check-prefix TRACE
> +// RUN: XRAY_OPTIONS="patch_premain=false xray_naive_log=false \
> +// RUN: xray_logfile_base=fdr-thread-order. xray_fdr_log=true verbosity=1 \
> +// RUN: xray_fdr_log_func_duration_threshold_us=0" %run %t 2>&1 | \
> +// RUN: FileCheck %s
> +// RUN: %llvm_xray convert --symbolize --output-format=yaml -instr_map=%t \
> +// RUN: "`ls fdr-thread-order.* | head -1`"
> +// RUN: %llvm_xray convert --symbolize --output-format=yaml -instr_map=%t \
> +// RUN: "`ls fdr-thread-order.* | head -1`" | \
> +// RUN: FileCheck %s --check-prefix TRACE
> // RUN: rm fdr-thread-order.*
> // FIXME: Make llvm-xray work on non-x86_64 as well.
> // REQUIRES: x86_64-linux
> // REQUIRES: built-in-llvm-tree
>
> #include "xray/xray_log_interface.h"
> -#include <thread>
> +#include <atomic>
> #include <cassert>
> +#include <thread>
>
> constexpr auto kBufferSize = 16384;
> constexpr auto kBufferMax = 10;
>
> -thread_local uint64_t var = 0;
> -[[clang::xray_always_instrument]] void __attribute__((noinline)) f1() { ++var; }
> -[[clang::xray_always_instrument]] void __attribute__((noinline)) f2() { ++var; }
> +std::atomic<uint64_t> var{0};
> +
> +[[clang::xray_always_instrument]] void __attribute__((noinline)) f1() {
> + for (auto i = 0; i < 1 << 20; ++i)
> + ++var;
> +}
> +
> +[[clang::xray_always_instrument]] void __attribute__((noinline)) f2() {
> + for (auto i = 0; i < 1 << 20; ++i)
> + ++var;
> +}
>
> int main(int argc, char *argv[]) {
> using namespace __xray;
> FDRLoggingOptions Options;
> + __xray_patch();
> assert(__xray_log_init(kBufferSize, kBufferMax, &Options,
> sizeof(FDRLoggingOptions)) ==
> XRayLogInitStatus::XRAY_LOG_INITIALIZED);
> - __xray_patch();
> - std::thread t1([] { f1(); });
> - std::thread t2([] { f2(); });
> - t1.join();
> - t2.join();
> +
> + std::atomic_thread_fence(std::memory_order_acq_rel);
> +
> + {
> + std::thread t1([] { f1(); });
> + std::thread t2([] { f2(); });
> + t1.join();
> + t2.join();
> + }
> +
> + std::atomic_thread_fence(std::memory_order_acq_rel);
> __xray_log_finalize();
> __xray_log_flushLog();
> + __xray_unpatch();
> + return var > 0 ? 0 : 1;
> // CHECK: {{.*}}XRay: Log file in '{{.*}}'
> + // CHECK-NOT: Failed
> }
>
> // We want to make sure that the order of the function log doesn't matter.
>
>
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