[compiler-rt] r314766 - [XRay][compiler-rt] Use a hand-written circular buffer in BufferQueue
Dean Michael Berris via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 3 04:39:31 PDT 2017
Hi Diana -- yes, I'll revert in the meantime.
> On 3 Oct 2017, at 20:10, Diana Picus <diana.picus at linaro.org> wrote:
>
> 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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