src/tracing/core/shared_memory_arbiter_impl.cc - platform/external/perfetto - Gitiles

 /*
  * Copyright (C) 2017 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "src/tracing/core/shared_memory_arbiter_impl.h"

 #include "perfetto/base/logging.h"
 #include "perfetto/base/task_runner.h"
 #include "perfetto/base/time.h"
 #include "perfetto/tracing/core/commit_data_request.h"
 #include "perfetto/tracing/core/shared_memory.h"
 #include "src/tracing/core/null_trace_writer.h"
 #include "src/tracing/core/trace_writer_impl.h"

 #include <limits>
 #include <utility>

 namespace perfetto {

 using Chunk = SharedMemoryABI::Chunk;

 // static
 SharedMemoryABI::PageLayout SharedMemoryArbiterImpl::default_page_layout =
     SharedMemoryABI::PageLayout::kPageDiv1;

 // static
 std::unique_ptr<SharedMemoryArbiter> SharedMemoryArbiter::CreateInstance(
     SharedMemory* shared_memory,
     size_t page_size,
     TracingService::ProducerEndpoint* producer_endpoint,
     base::TaskRunner* task_runner) {
   return std::unique_ptr<SharedMemoryArbiterImpl>(
       new SharedMemoryArbiterImpl(shared_memory->start(), shared_memory->size(),
                                   page_size, producer_endpoint, task_runner));
 }

 SharedMemoryArbiterImpl::SharedMemoryArbiterImpl(
     void* start,
     size_t size,
     size_t page_size,
     TracingService::ProducerEndpoint* producer_endpoint,
     base::TaskRunner* task_runner)
     : task_runner_(task_runner),
       producer_endpoint_(producer_endpoint),
       shmem_abi_(reinterpret_cast<uint8_t*>(start), size, page_size),
       active_writer_ids_(kMaxWriterID),
       weak_ptr_factory_(this) {}

 Chunk SharedMemoryArbiterImpl::GetNewChunk(
     const SharedMemoryABI::ChunkHeader& header,
     size_t size_hint) {
   PERFETTO_DCHECK(size_hint == 0);  // Not implemented yet.
   int stall_count = 0;
   unsigned stall_interval_us = 0;
   static const unsigned kMaxStallIntervalUs = 100000;
   static const int kLogAfterNStalls = 3;

   for (;;) {
     // TODO(primiano): Probably this lock is not really required and this code
     // could be rewritten leveraging only the Try* atomic operations in
     // SharedMemoryABI. But let's not be too adventurous for the moment.
     {
       std::lock_guard<std::mutex> scoped_lock(lock_);
       const size_t initial_page_idx = page_idx_;
       for (size_t i = 0; i < shmem_abi_.num_pages(); i++) {
         page_idx_ = (initial_page_idx + i) % shmem_abi_.num_pages();
         bool is_new_page = false;

         // TODO(primiano): make the page layout dynamic.
         auto layout = SharedMemoryArbiterImpl::default_page_layout;

         if (shmem_abi_.is_page_free(page_idx_)) {
           // TODO(primiano): Use the |size_hint| here to decide the layout.
           is_new_page = shmem_abi_.TryPartitionPage(page_idx_, layout);
         }
         uint32_t free_chunks;
         if (is_new_page) {
           free_chunks = (1 << SharedMemoryABI::kNumChunksForLayout[layout]) - 1;
         } else {
           free_chunks = shmem_abi_.GetFreeChunks(page_idx_);
         }

         for (uint32_t chunk_idx = 0; free_chunks;
              chunk_idx++, free_chunks >>= 1) {
           if (!(free_chunks & 1))
             continue;
           // We found a free chunk.
           Chunk chunk = shmem_abi_.TryAcquireChunkForWriting(
               page_idx_, chunk_idx, &header);
           if (!chunk.is_valid())
             continue;
           if (stall_count > kLogAfterNStalls) {
             PERFETTO_LOG("Recovered from stall after %d iterations",
                          stall_count);
           }
           return chunk;
         }
       }
     }  // std::lock_guard<std::mutex>

     // All chunks are taken (either kBeingWritten by us or kBeingRead by the
     // Service). TODO: at this point we should return a bankrupcy chunk, not
     // crash the process.
     if (stall_count++ == kLogAfterNStalls) {
       PERFETTO_ELOG("Shared memory buffer overrun! Stalling");

       // TODO(primiano): sending the IPC synchronously is a temporary workaround
       // until the backpressure logic in probes_producer is sorted out. Until
       // then the risk is that we stall the message loop waiting for the
       // tracing service to  consume the shared memory buffer (SMB) and, for
       // this reason, never run the task that tells the service to purge the
       // SMB.
       FlushPendingCommitDataRequests();
     }
     base::SleepMicroseconds(stall_interval_us);
     stall_interval_us =
         std::min(kMaxStallIntervalUs, (stall_interval_us + 1) * 8);
   }
 }

 void SharedMemoryArbiterImpl::ReturnCompletedChunk(Chunk chunk,
                                                    BufferID target_buffer,
                                                    PatchList* patch_list) {
   bool should_post_callback = false;
   bool should_commit_synchronously = false;
   base::WeakPtr<SharedMemoryArbiterImpl> weak_this;
   {
     std::lock_guard<std::mutex> scoped_lock(lock_);
     uint8_t chunk_idx = chunk.chunk_idx();
     const WriterID writer_id = chunk.writer_id();
     bytes_pending_commit_ += chunk.size();
     size_t page_idx = shmem_abi_.ReleaseChunkAsComplete(std::move(chunk));

     // DO NOT access |chunk| after this point, has been std::move()-d above.

     if (!commit_data_req_) {
       commit_data_req_.reset(new CommitDataRequest());
       weak_this = weak_ptr_factory_.GetWeakPtr();
       should_post_callback = true;
     }
     CommitDataRequest::ChunksToMove* ctm =
         commit_data_req_->add_chunks_to_move();
     ctm->set_page(static_cast<uint32_t>(page_idx));
     ctm->set_chunk(chunk_idx);
     ctm->set_target_buffer(target_buffer);

     // If more than half of the SMB.size() is filled with completed chunks for
     // which we haven't notified the service yet (i.e. they are still enqueued
     // in |commit_data_req_|), force a synchronous CommitDataRequest(), to
     // reduce the likeliness of stalling the writer.
     if (bytes_pending_commit_ >= shmem_abi_.size() / 2) {
       should_commit_synchronously = true;
       should_post_callback = false;
     }

     // Get the patches completed for the previous chunk from the |patch_list|
     // and update it.
     ChunkID last_chunk_id = 0;  // 0 is irrelevant but keeps the compiler happy.
     CommitDataRequest::ChunkToPatch* last_chunk_req = nullptr;
     while (!patch_list->empty() && patch_list->front().is_patched()) {
       if (!last_chunk_req || last_chunk_id != patch_list->front().chunk_id) {
         last_chunk_req = commit_data_req_->add_chunks_to_patch();
         last_chunk_req->set_writer_id(writer_id);
         last_chunk_id = patch_list->front().chunk_id;
         last_chunk_req->set_chunk_id(last_chunk_id);
         last_chunk_req->set_target_buffer(target_buffer);
       }
       auto* patch_req = last_chunk_req->add_patches();
       patch_req->set_offset(patch_list->front().offset);
       patch_req->set_data(&patch_list->front().size_field[0],
                           patch_list->front().size_field.size());
       patch_list->pop_front();
     }
     // Patches are enqueued in the |patch_list| in order and are notified to
     // the service when the chunk is returned. The only case when the current
     // patch list is incomplete is if there is an unpatched entry at the head of
     // the |patch_list| that belongs to the same ChunkID as the last one we are
     // about to send to the service.
     if (last_chunk_req && !patch_list->empty() &&
         patch_list->front().chunk_id == last_chunk_id) {
       last_chunk_req->set_has_more_patches(true);
     }
   }  // scoped_lock(lock_)

   if (should_post_callback) {
     PERFETTO_DCHECK(weak_this);
     task_runner_->PostTask([weak_this] {
       if (weak_this)
         weak_this->FlushPendingCommitDataRequests();
     });
   }

   if (should_commit_synchronously)
     FlushPendingCommitDataRequests();
 }

 // TODO(primiano): this is wrong w.r.t. threading because it will try to send
 // an IPC from a different thread than the IPC thread. Right now this works
 // because everything is single threaded. It will hit the thread checker
 // otherwise. What we really want to do here is doing this sync IPC only if
 // task_runner_.RunsTaskOnCurrentThread(), otherwise PostTask().
 void SharedMemoryArbiterImpl::FlushPendingCommitDataRequests(
     std::function<void()> callback) {
   PERFETTO_DCHECK_THREAD(thread_checker_);

   std::unique_ptr<CommitDataRequest> req;
   {
     std::lock_guard<std::mutex> scoped_lock(lock_);
     req = std::move(commit_data_req_);
     bytes_pending_commit_ = 0;
   }
   // |commit_data_req_| could become nullptr if the forced sync flush happens
   // in GetNewChunk().
   if (req) {
     producer_endpoint_->CommitData(*req, callback);
   } else if (callback) {
     // If |commit_data_req_| was nullptr, it means that an enqueued deferred
     // commit was executed just before this. At this point send an empty commit
     // request to the service, just to linearize with it and give the guarantee
     // to the caller that the data has been flushed into the service.
     producer_endpoint_->CommitData(CommitDataRequest(), callback);
   }
 }

 std::unique_ptr<TraceWriter> SharedMemoryArbiterImpl::CreateTraceWriter(
     BufferID target_buffer) {
   WriterID id;
   {
     std::lock_guard<std::mutex> scoped_lock(lock_);
     id = active_writer_ids_.Allocate();
   }
   if (!id)
     return std::unique_ptr<TraceWriter>(new NullTraceWriter());
   return std::unique_ptr<TraceWriter>(
       new TraceWriterImpl(this, id, target_buffer));
 }

 void SharedMemoryArbiterImpl::NotifyFlushComplete(FlushRequestID req_id) {
   bool should_post_commit_task = false;
   {
     std::lock_guard<std::mutex> scoped_lock(lock_);
     // If a commit_data_req_ exists it means that somebody else already posted a
     // FlushPendingCommitDataRequests() task.
     if (!commit_data_req_) {
       commit_data_req_.reset(new CommitDataRequest());
       should_post_commit_task = true;
     } else {
       // If there is another request queued and that also contains is a reply
       // to a flush request, reply with the highest id.
       req_id = std::max(req_id, commit_data_req_->flush_request_id());
     }
     commit_data_req_->set_flush_request_id(req_id);
   }
   if (should_post_commit_task) {
     auto weak_this = weak_ptr_factory_.GetWeakPtr();
     task_runner_->PostTask([weak_this] {
       if (weak_this)
         weak_this->FlushPendingCommitDataRequests();
     });
   }
 }

 void SharedMemoryArbiterImpl::ReleaseWriterID(WriterID id) {
   std::lock_guard<std::mutex> scoped_lock(lock_);
   active_writer_ids_.Free(id);
 }

 }  // namespace perfetto
	/*
	* Copyright (C) 2017 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "src/tracing/core/shared_memory_arbiter_impl.h"

	#include "perfetto/base/logging.h"
	#include "perfetto/base/task_runner.h"
	#include "perfetto/base/time.h"
	#include "perfetto/tracing/core/commit_data_request.h"
	#include "perfetto/tracing/core/shared_memory.h"
	#include "src/tracing/core/null_trace_writer.h"
	#include "src/tracing/core/trace_writer_impl.h"

	#include <limits>
	#include <utility>

	namespace perfetto {

	using Chunk = SharedMemoryABI::Chunk;

	// static
	SharedMemoryABI::PageLayout SharedMemoryArbiterImpl::default_page_layout =
	SharedMemoryABI::PageLayout::kPageDiv1;

	// static
	std::unique_ptr<SharedMemoryArbiter> SharedMemoryArbiter::CreateInstance(
	SharedMemory* shared_memory,
	size_t page_size,
	TracingService::ProducerEndpoint* producer_endpoint,
	base::TaskRunner* task_runner) {
	return std::unique_ptr<SharedMemoryArbiterImpl>(
	new SharedMemoryArbiterImpl(shared_memory->start(), shared_memory->size(),
	page_size, producer_endpoint, task_runner));
	}

	SharedMemoryArbiterImpl::SharedMemoryArbiterImpl(
	void* start,
	size_t size,
	size_t page_size,
	TracingService::ProducerEndpoint* producer_endpoint,
	base::TaskRunner* task_runner)
	: task_runner_(task_runner),
	producer_endpoint_(producer_endpoint),
	shmem_abi_(reinterpret_cast<uint8_t*>(start), size, page_size),
	active_writer_ids_(kMaxWriterID),
	weak_ptr_factory_(this) {}

	Chunk SharedMemoryArbiterImpl::GetNewChunk(
	const SharedMemoryABI::ChunkHeader& header,
	size_t size_hint) {
	PERFETTO_DCHECK(size_hint == 0); // Not implemented yet.
	int stall_count = 0;
	unsigned stall_interval_us = 0;
	static const unsigned kMaxStallIntervalUs = 100000;
	static const int kLogAfterNStalls = 3;

	for (;;) {
	// TODO(primiano): Probably this lock is not really required and this code
	// could be rewritten leveraging only the Try* atomic operations in
	// SharedMemoryABI. But let's not be too adventurous for the moment.
	{
	std::lock_guard<std::mutex> scoped_lock(lock_);
	const size_t initial_page_idx = page_idx_;
	for (size_t i = 0; i < shmem_abi_.num_pages(); i++) {
	page_idx_ = (initial_page_idx + i) % shmem_abi_.num_pages();
	bool is_new_page = false;

	// TODO(primiano): make the page layout dynamic.
	auto layout = SharedMemoryArbiterImpl::default_page_layout;

	if (shmem_abi_.is_page_free(page_idx_)) {
	// TODO(primiano): Use the \|size_hint\| here to decide the layout.
	is_new_page = shmem_abi_.TryPartitionPage(page_idx_, layout);
	}
	uint32_t free_chunks;
	if (is_new_page) {
	free_chunks = (1 << SharedMemoryABI::kNumChunksForLayout[layout]) - 1;
	} else {
	free_chunks = shmem_abi_.GetFreeChunks(page_idx_);
	}

	for (uint32_t chunk_idx = 0; free_chunks;
	chunk_idx++, free_chunks >>= 1) {
	if (!(free_chunks & 1))
	continue;
	// We found a free chunk.
	Chunk chunk = shmem_abi_.TryAcquireChunkForWriting(
	page_idx_, chunk_idx, &header);
	if (!chunk.is_valid())
	continue;
	if (stall_count > kLogAfterNStalls) {
	PERFETTO_LOG("Recovered from stall after %d iterations",
	stall_count);
	}
	return chunk;
	}
	}
	} // std::lock_guard<std::mutex>

	// All chunks are taken (either kBeingWritten by us or kBeingRead by the
	// Service). TODO: at this point we should return a bankrupcy chunk, not
	// crash the process.
	if (stall_count++ == kLogAfterNStalls) {
	PERFETTO_ELOG("Shared memory buffer overrun! Stalling");

	// TODO(primiano): sending the IPC synchronously is a temporary workaround
	// until the backpressure logic in probes_producer is sorted out. Until
	// then the risk is that we stall the message loop waiting for the
	// tracing service to consume the shared memory buffer (SMB) and, for
	// this reason, never run the task that tells the service to purge the
	// SMB.
	FlushPendingCommitDataRequests();
	}
	base::SleepMicroseconds(stall_interval_us);
	stall_interval_us =
	std::min(kMaxStallIntervalUs, (stall_interval_us + 1) * 8);
	}
	}

	void SharedMemoryArbiterImpl::ReturnCompletedChunk(Chunk chunk,
	BufferID target_buffer,
	PatchList* patch_list) {
	bool should_post_callback = false;
	bool should_commit_synchronously = false;
	base::WeakPtr<SharedMemoryArbiterImpl> weak_this;
	{
	std::lock_guard<std::mutex> scoped_lock(lock_);
	uint8_t chunk_idx = chunk.chunk_idx();
	const WriterID writer_id = chunk.writer_id();
	bytes_pending_commit_ += chunk.size();
	size_t page_idx = shmem_abi_.ReleaseChunkAsComplete(std::move(chunk));

	// DO NOT access \|chunk\| after this point, has been std::move()-d above.

	if (!commit_data_req_) {
	commit_data_req_.reset(new CommitDataRequest());
	weak_this = weak_ptr_factory_.GetWeakPtr();
	should_post_callback = true;
	}
	CommitDataRequest::ChunksToMove* ctm =
	commit_data_req_->add_chunks_to_move();
	ctm->set_page(static_cast<uint32_t>(page_idx));
	ctm->set_chunk(chunk_idx);
	ctm->set_target_buffer(target_buffer);

	// If more than half of the SMB.size() is filled with completed chunks for
	// which we haven't notified the service yet (i.e. they are still enqueued
	// in \|commit_data_req_\|), force a synchronous CommitDataRequest(), to
	// reduce the likeliness of stalling the writer.
	if (bytes_pending_commit_ >= shmem_abi_.size() / 2) {
	should_commit_synchronously = true;
	should_post_callback = false;
	}

	// Get the patches completed for the previous chunk from the \|patch_list\|
	// and update it.
	ChunkID last_chunk_id = 0; // 0 is irrelevant but keeps the compiler happy.
	CommitDataRequest::ChunkToPatch* last_chunk_req = nullptr;
	while (!patch_list->empty() && patch_list->front().is_patched()) {
	if (!last_chunk_req \|\| last_chunk_id != patch_list->front().chunk_id) {
	last_chunk_req = commit_data_req_->add_chunks_to_patch();
	last_chunk_req->set_writer_id(writer_id);
	last_chunk_id = patch_list->front().chunk_id;
	last_chunk_req->set_chunk_id(last_chunk_id);
	last_chunk_req->set_target_buffer(target_buffer);
	}
	auto* patch_req = last_chunk_req->add_patches();
	patch_req->set_offset(patch_list->front().offset);
	patch_req->set_data(&patch_list->front().size_field[0],
	patch_list->front().size_field.size());
	patch_list->pop_front();
	}
	// Patches are enqueued in the \|patch_list\| in order and are notified to
	// the service when the chunk is returned. The only case when the current
	// patch list is incomplete is if there is an unpatched entry at the head of
	// the \|patch_list\| that belongs to the same ChunkID as the last one we are
	// about to send to the service.
	if (last_chunk_req && !patch_list->empty() &&
	patch_list->front().chunk_id == last_chunk_id) {
	last_chunk_req->set_has_more_patches(true);
	}
	} // scoped_lock(lock_)

	if (should_post_callback) {
	PERFETTO_DCHECK(weak_this);
	task_runner_->PostTask([weak_this] {
	if (weak_this)
	weak_this->FlushPendingCommitDataRequests();
	});
	}

	if (should_commit_synchronously)
	FlushPendingCommitDataRequests();
	}

	// TODO(primiano): this is wrong w.r.t. threading because it will try to send
	// an IPC from a different thread than the IPC thread. Right now this works
	// because everything is single threaded. It will hit the thread checker
	// otherwise. What we really want to do here is doing this sync IPC only if
	// task_runner_.RunsTaskOnCurrentThread(), otherwise PostTask().
	void SharedMemoryArbiterImpl::FlushPendingCommitDataRequests(
	std::function<void()> callback) {
	PERFETTO_DCHECK_THREAD(thread_checker_);

	std::unique_ptr<CommitDataRequest> req;
	{
	std::lock_guard<std::mutex> scoped_lock(lock_);
	req = std::move(commit_data_req_);
	bytes_pending_commit_ = 0;
	}
	// \|commit_data_req_\| could become nullptr if the forced sync flush happens
	// in GetNewChunk().
	if (req) {
	producer_endpoint_->CommitData(*req, callback);
	} else if (callback) {
	// If \|commit_data_req_\| was nullptr, it means that an enqueued deferred
	// commit was executed just before this. At this point send an empty commit
	// request to the service, just to linearize with it and give the guarantee
	// to the caller that the data has been flushed into the service.
	producer_endpoint_->CommitData(CommitDataRequest(), callback);
	}
	}

	std::unique_ptr<TraceWriter> SharedMemoryArbiterImpl::CreateTraceWriter(
	BufferID target_buffer) {
	WriterID id;
	{
	std::lock_guard<std::mutex> scoped_lock(lock_);
	id = active_writer_ids_.Allocate();
	}
	if (!id)
	return std::unique_ptr<TraceWriter>(new NullTraceWriter());
	return std::unique_ptr<TraceWriter>(
	new TraceWriterImpl(this, id, target_buffer));
	}

	void SharedMemoryArbiterImpl::NotifyFlushComplete(FlushRequestID req_id) {
	bool should_post_commit_task = false;
	{
	std::lock_guard<std::mutex> scoped_lock(lock_);
	// If a commit_data_req_ exists it means that somebody else already posted a
	// FlushPendingCommitDataRequests() task.
	if (!commit_data_req_) {
	commit_data_req_.reset(new CommitDataRequest());
	should_post_commit_task = true;
	} else {
	// If there is another request queued and that also contains is a reply
	// to a flush request, reply with the highest id.
	req_id = std::max(req_id, commit_data_req_->flush_request_id());
	}
	commit_data_req_->set_flush_request_id(req_id);
	}
	if (should_post_commit_task) {
	auto weak_this = weak_ptr_factory_.GetWeakPtr();
	task_runner_->PostTask([weak_this] {
	if (weak_this)
	weak_this->FlushPendingCommitDataRequests();
	});
	}
	}

	void SharedMemoryArbiterImpl::ReleaseWriterID(WriterID id) {
	std::lock_guard<std::mutex> scoped_lock(lock_);
	active_writer_ids_.Free(id);
	}

	} // namespace perfetto