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Commit 31e04264 authored by Akilesh Kailash's avatar Akilesh Kailash
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libsnapshot:snapuserd: mmap + msync header after merge 



mmap the CowHeader and use msync to flush only the
first 4k page after merge is complete.

This cuts down ~30 seconds of merge completion time
on a 55M incremental OTA with 235k copy operations.

Although, this isn't a significant gain but this patch
creates a scaffolding for the next set of read-ahead patches.

Bug: 183863613
Test: Incremental and Full OTA
Signed-off-by: default avatarAkilesh Kailash <akailash@google.com>
Change-Id: I15bfec91ea1d5bdf4390670bcf406e1015b79299
parent acc1c5d1

fs_mgr/libsnapshot/cow_writer.cpp

+0 −24
Original line number Diff line number Diff line
@@ -139,12 +139,6 @@ bool CowWriter::SetFd(android::base::borrowed_fd fd) { 
    return true;

}



void CowWriter::InitializeMerge(borrowed_fd fd, CowHeader* header) {

    fd_ = fd;

    memcpy(&header_, header, sizeof(CowHeader));

    merge_in_progress_ = true;

}



bool CowWriter::Initialize(unique_fd&& fd) {

    owned_fd_ = std::move(fd);

    return Initialize(borrowed_fd{owned_fd_});
@@ -517,24 +511,6 @@ bool CowWriter::Sync() { 
    return true;

}



bool CowWriter::CommitMerge(int merged_ops) {

    CHECK(merge_in_progress_);

    header_.num_merge_ops += merged_ops;



    if (lseek(fd_.get(), 0, SEEK_SET) < 0) {

        PLOG(ERROR) << "lseek failed";

        return false;

    }



    if (!android::base::WriteFully(fd_, reinterpret_cast<const uint8_t*>(&header_),

                                   sizeof(header_))) {

        PLOG(ERROR) << "WriteFully failed";

        return false;

    }



    return Sync();

}



bool CowWriter::Truncate(off_t length) {

    if (is_dev_null_ || is_block_device_) {

        return true;

fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h

+0 −3
Original line number Diff line number Diff line
@@ -100,9 +100,6 @@ class CowWriter : public ICowWriter { 
    bool InitializeAppend(android::base::unique_fd&&, uint64_t label);

    bool InitializeAppend(android::base::borrowed_fd fd, uint64_t label);



    void InitializeMerge(android::base::borrowed_fd fd, CowHeader* header);

    bool CommitMerge(int merged_ops);



    bool Finalize() override;



    uint64_t GetCowSize() override;

fs_mgr/libsnapshot/snapuserd.cpp

+40 −18
Original line number Diff line number Diff line
@@ -51,20 +51,17 @@ bool Snapuserd::InitializeWorkers() { 
}



bool Snapuserd::CommitMerge(int num_merge_ops) {

    {

        std::lock_guard<std::mutex> lock(lock_);

        CowHeader header;

    struct CowHeader* ch = reinterpret_cast<struct CowHeader*>(mapped_addr_);

    ch->num_merge_ops += num_merge_ops;



        reader_->GetHeader(&header);

        header.num_merge_ops += num_merge_ops;

        reader_->UpdateMergeProgress(num_merge_ops);

        if (!writer_->CommitMerge(num_merge_ops)) {

            SNAP_LOG(ERROR) << "CommitMerge failed... merged_ops_cur_iter: " << num_merge_ops

                            << " Total-merged-ops: " << header.num_merge_ops;

    // Sync the first 4k block

    int ret = msync(mapped_addr_, BLOCK_SZ, MS_SYNC);

    if (ret < 0) {

        PLOG(ERROR) << "msync header failed: " << ret;

        return false;

    }



    merge_initiated_ = true;

    }



    return true;

}
@@ -93,9 +90,9 @@ void Snapuserd::CheckMergeCompletionStatus() { 
        return;

    }



    CowHeader header;

    reader_->GetHeader(&header);

    SNAP_LOG(INFO) << "Merge-status: Total-Merged-ops: " << header.num_merge_ops

    struct CowHeader* ch = reinterpret_cast<struct CowHeader*>(mapped_addr_);



    SNAP_LOG(INFO) << "Merge-status: Total-Merged-ops: " << ch->num_merge_ops

                   << " Total-data-ops: " << reader_->total_data_ops();

}
@@ -175,8 +172,10 @@ bool Snapuserd::ReadMetadata() { 
    reader_->InitializeMerge();

    SNAP_LOG(DEBUG) << "Merge-ops: " << header.num_merge_ops;



    writer_ = std::make_unique<CowWriter>(options);

    writer_->InitializeMerge(cow_fd_.get(), &header);

    if (!MmapMetadata()) {

        SNAP_LOG(ERROR) << "mmap failed";

        return false;

    }



    // Initialize the iterator for reading metadata

    cowop_riter_ = reader_->GetRevOpIter();
@@ -487,6 +486,29 @@ bool Snapuserd::ReadMetadata() { 
    return true;

}



bool Snapuserd::MmapMetadata() {

    CowHeader header;

    reader_->GetHeader(&header);



    // mmap the first 4k page

    total_mapped_addr_length_ = BLOCK_SZ;

    mapped_addr_ = mmap(NULL, total_mapped_addr_length_, PROT_READ | PROT_WRITE, MAP_SHARED,

                        cow_fd_.get(), 0);

    if (mapped_addr_ == MAP_FAILED) {

        SNAP_LOG(ERROR) << "mmap metadata failed";

        return false;

    }



    return true;

}



void Snapuserd::UnmapBufferRegion() {

    int ret = munmap(mapped_addr_, total_mapped_addr_length_);

    if (ret < 0) {

        SNAP_PLOG(ERROR) << "munmap failed";

    }

}



void MyLogger(android::base::LogId, android::base::LogSeverity severity, const char*, const char*,

              unsigned int, const char* message) {

    if (severity == android::base::ERROR) {

fs_mgr/libsnapshot/snapuserd.h

+8 −3
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/types.h>

#include <stdint.h>

#include <stdlib.h>

#include <sys/mman.h>



#include <bitset>

#include <csignal>
@@ -173,9 +174,10 @@ class Snapuserd : public std::enable_shared_from_this<Snapuserd> { 
        return p1.first < p2.first;

    }



  private:

    std::vector<std::unique_ptr<WorkerThread>> worker_threads_;

    void UnmapBufferRegion();

    bool MmapMetadata();



  private:

    bool IsChunkIdMetadata(chunk_t chunk);

    chunk_t GetNextAllocatableChunkId(chunk_t chunk_id);
@@ -197,7 +199,6 @@ class Snapuserd : public std::enable_shared_from_this<Snapuserd> { 
    std::unique_ptr<ICowOpIter> cowop_iter_;

    std::unique_ptr<ICowOpReverseIter> cowop_riter_;

    std::unique_ptr<CowReader> reader_;

    std::unique_ptr<CowWriter> writer_;



    // Vector of disk exception which is a

    // mapping of old-chunk to new-chunk
@@ -209,6 +210,10 @@ class Snapuserd : public std::enable_shared_from_this<Snapuserd> { 


    std::mutex lock_;



    void* mapped_addr_;

    size_t total_mapped_addr_length_;



    std::vector<std::unique_ptr<WorkerThread>> worker_threads_;

    bool merge_initiated_ = false;

    bool attached_ = false;

};

fs_mgr/libsnapshot/snapuserd_server.cpp

+2 −1
Original line number Diff line number Diff line
@@ -209,10 +209,11 @@ void SnapuserdServer::RunThread(std::shared_ptr<DmUserHandler> handler) { 
    }



    handler->snapuserd()->CloseFds();

    handler->snapuserd()->CheckMergeCompletionStatus();

    handler->snapuserd()->UnmapBufferRegion();



    auto misc_name = handler->misc_name();

    LOG(INFO) << "Handler thread about to exit: " << misc_name;

    handler->snapuserd()->CheckMergeCompletionStatus();



    {

        std::lock_guard<std::mutex> lock(lock_);