Merge "Merge "Revert "Resend remaining VMAs on partial compaction due to...

// Defines the maximum amount of VMAs we can send per process_madvise syscall.

// Currently this is set to UIO_MAXIOV which is the maximum segments allowed by

// iovec implementation used by process_madvise syscall

#define MAX_VMAS_PER_BATCH UIO_MAXIOV

#define MAX_VMAS_PER_COMPACTION UIO_MAXIOV

// Maximum bytes that we can send per process_madvise syscall once this limit

// is reached we split the remaining VMAs into another syscall. The MAX_RW_COUNT

// limit is imposed by iovec implementation. However, if you want to use a smaller

// limit, it has to be a page aligned value.

#define MAX_BYTES_PER_BATCH MAX_RW_COUNT

// limit, it has to be a page aligned value, otherwise, compaction would fail.

#define MAX_BYTES_PER_COMPACTION MAX_RW_COUNT

// Selected a high enough number to avoid clashing with linux errno codes

#define ERROR_COMPACTION_CANCELLED -1000

// before starting next VMA batch

static std::atomic<bool> cancelRunningCompaction;

// A VmaBatch represents a set of VMAs that can be processed

// as VMAs are processed by client code it is expected that the

// VMAs get consumed which means they are discarded as they are

// processed so that the first element always is the next element

// to be sent

struct VmaBatch {

    struct iovec* vmas;

    // total amount of VMAs to reach the end of iovec

    int totalVmas;

    // total amount of bytes that are remaining within iovec

    uint64_t totalBytes;

};

// Advances the iterator by the specified amount of bytes.

// This is used to remove already processed or no longer

// needed parts of the batch.

// Returns total bytes consumed

int consumeBytes(VmaBatch& batch, uint64_t bytesToConsume) {

    int index = 0;

    if (CC_UNLIKELY(bytesToConsume) < 0) {

        LOG(ERROR) << "Cannot consume negative bytes for VMA batch !";

        return 0;

    }

    if (bytesToConsume > batch.totalBytes) {

        // Avoid consuming more bytes than available

        bytesToConsume = batch.totalBytes;

    }

    uint64_t bytesConsumed = 0;

    while (bytesConsumed < bytesToConsume) {

        if (CC_UNLIKELY(index >= batch.totalVmas)) {

            // reach the end of the batch

            return bytesConsumed;

        }

        if (CC_UNLIKELY(bytesConsumed + batch.vmas[index].iov_len > bytesToConsume)) {

            // this is the whole VMA that will be consumed

            break;

        }

        bytesConsumed += batch.vmas[index].iov_len;

        batch.totalBytes -= batch.vmas[index].iov_len;

        --batch.totalVmas;

        ++index;

    }

    // Move pointer to consume all the whole VMAs

    batch.vmas = batch.vmas + index;

    // Consume the rest of the bytes partially at last VMA in batch

    uint64_t bytesLeftToConsume = bytesToConsume - bytesConsumed;

    bytesConsumed += bytesLeftToConsume;

    if (batch.totalVmas > 0) {

        batch.vmas[0].iov_base = (void*)((uint64_t)batch.vmas[0].iov_base + bytesLeftToConsume);

    }

    return bytesConsumed;

}

// given a source of vmas this class will act as a factory

// of VmaBatch objects and it will allow generating batches

// until there are no more left in the source vector.

// Note: the class does not actually modify the given

// vmas vector, instead it iterates on it until the end.

class VmaBatchCreator {

    const std::vector<Vma>* sourceVmas;

    // This is the destination array where batched VMAs will be stored

    // it gets encapsulated into a VmaBatch which is the object

    // meant to be used by client code.

    struct iovec* destVmas;

    // Parameters to keep track of the iterator on the source vmas

    int currentIndex_;

    uint64_t currentOffset_;

public:

    VmaBatchCreator(const std::vector<Vma>* vmasToBatch, struct iovec* destVmasVec)

          : sourceVmas(vmasToBatch), destVmas(destVmasVec), currentIndex_(0), currentOffset_(0) {}

    int currentIndex() { return currentIndex_; }

    uint64_t currentOffset() { return currentOffset_; }

    // Generates a batch and moves the iterator on the source vmas

    // past the last VMA in the batch.

    // Returns true on success, false on failure

    bool createNextBatch(VmaBatch& batch) {

        if (currentIndex_ >= MAX_VMAS_PER_BATCH && currentIndex_ >= sourceVmas->size()) {

            return false;

        }

        const std::vector<Vma>& vmas = *sourceVmas;

        batch.vmas = destVmas;

        uint64_t totalBytesInBatch = 0;

        int indexInBatch = 0;

        // Add VMAs to the batch up until we consumed all the VMAs or

        // reached any imposed limit of VMAs per batch.

        while (indexInBatch < MAX_VMAS_PER_BATCH && currentIndex_ < vmas.size()) {

            uint64_t vmaStart = vmas[currentIndex_].start + currentOffset_;

            uint64_t vmaSize = vmas[currentIndex_].end - vmaStart;

            if (CC_UNLIKELY(vmaSize == 0)) {

                // No more bytes to batch for this VMA, move to next one

                // this only happens if a batch partially consumed bytes

                // and offset landed at exactly the end of a vma

                continue;

            }

            batch.vmas[indexInBatch].iov_base = (void*)vmaStart;

            uint64_t bytesAvailableInBatch = MAX_BYTES_PER_BATCH - totalBytesInBatch;

            if (vmaSize >= bytesAvailableInBatch) {

                // VMA would exceed the max available bytes in batch

                // clamp with available bytes and finish batch.

                vmaSize = bytesAvailableInBatch;

                currentOffset_ += bytesAvailableInBatch;

            }

            batch.vmas[indexInBatch].iov_len = vmaSize;

            totalBytesInBatch += vmaSize;

            ++indexInBatch;

            if (totalBytesInBatch >= MAX_BYTES_PER_BATCH) {

                // Reached max bytes quota so this marks

                // the end of the batch

                break;

            }

            // Fully finished current VMA, move to next one

            currentOffset_ = 0;

            ++currentIndex_;

        }

        // Vmas where fully filled and we are past the last filled index.

        batch.totalVmas = indexInBatch;

        batch.totalBytes = totalBytesInBatch;

        return true;

    }

};

// Madvise a set of VMAs given in a batch for a specific process

// The total number of bytes successfully madvised will be set on

// outBytesProcessed.

// Returns 0 on success and standard linux -errno code returned by

// process_madvise on failure

int madviseVmasFromBatch(unique_fd& pidfd, VmaBatch& batch, int madviseType,

                         uint64_t* outBytesProcessed) {

    if (batch.totalVmas == 0) {

        // No VMAs in Batch, skip.

        *outBytesProcessed = 0;

        return 0;

    }

    ATRACE_BEGIN(StringPrintf("Madvise %d: %d VMAs", madviseType, batch.totalVmas).c_str());

    uint64_t bytesProcessedInSend =

            process_madvise(pidfd, batch.vmas, batch.totalVmas, madviseType, 0);

    ATRACE_END();

    if (CC_UNLIKELY(bytesProcessedInSend == -1)) {

        bytesProcessedInSend = 0;

        if (errno != EINVAL) {

            // Forward irrecoverable errors and bail out compaction

            *outBytesProcessed = 0;

            return -errno;

        }

    }

    if (bytesProcessedInSend < batch.totalBytes) {

        // Did not process all the bytes requested

        // skip last page which likely failed

        bytesProcessedInSend += PAGE_SIZE;

    }

    bytesProcessedInSend = consumeBytes(batch, bytesProcessedInSend);

    *outBytesProcessed = bytesProcessedInSend;

    return 0;

}

// Legacy method for compacting processes, any new code should

// use compactProcess instead.

static inline void compactProcessProcfs(int pid, const std::string& compactionType) {

// If any VMA fails compaction due to -EINVAL it will be skipped and continue.

// However, if it fails for any other reason, it will bail out and forward the error

static int64_t compactMemory(const std::vector<Vma>& vmas, int pid, int madviseType) {

    static struct iovec vmasToKernel[MAX_VMAS_PER_COMPACTION];

    if (vmas.empty()) {

        return 0;

    }

        return -errno;

    }

    struct iovec destVmas[MAX_VMAS_PER_BATCH];

    VmaBatch batch;

    VmaBatchCreator batcher(&vmas, destVmas);

    int64_t totalBytesProcessed = 0;

    while (batcher.createNextBatch(batch)) {

        uint64_t bytesProcessedInSend;

        do {

    int64_t vmaOffset = 0;

    for (int iVma = 0; iVma < vmas.size();) {

        uint64_t bytesSentToCompact = 0;

        int iVec = 0;

        while (iVec < MAX_VMAS_PER_COMPACTION && iVma < vmas.size()) {

            if (CC_UNLIKELY(cancelRunningCompaction.load())) {

                // There could be a significant delay between when a compaction

                // is requested and when it is handled during this time our

                                         StringPrintf("Cancelled compaction for %d", pid).c_str());

                return ERROR_COMPACTION_CANCELLED;

            }

            int error = madviseVmasFromBatch(pidfd, batch, madviseType, &bytesProcessedInSend);

            if (error < 0) {

                // Returns standard linux errno code

                return error;

            uint64_t vmaStart = vmas[iVma].start + vmaOffset;

            uint64_t vmaSize = vmas[iVma].end - vmaStart;

            if (vmaSize == 0) {

                goto next_vma;

            }

            vmasToKernel[iVec].iov_base = (void*)vmaStart;

            if (vmaSize > MAX_BYTES_PER_COMPACTION - bytesSentToCompact) {

                // Exceeded the max bytes that could be sent, so clamp

                // the end to avoid exceeding limit and issue compaction

                vmaSize = MAX_BYTES_PER_COMPACTION - bytesSentToCompact;

            }

            totalBytesProcessed += bytesProcessedInSend;

        } while (batch.totalBytes > 0);

            vmasToKernel[iVec].iov_len = vmaSize;

            bytesSentToCompact += vmaSize;

            ++iVec;

            if (bytesSentToCompact >= MAX_BYTES_PER_COMPACTION) {

                // Ran out of bytes within iovec, dispatch compaction.

                vmaOffset += vmaSize;

                break;

            }

        next_vma:

            // Finished current VMA, and have more bytes remaining

            vmaOffset = 0;

            ++iVma;

        }

        ATRACE_BEGIN(StringPrintf("Compact %d VMAs", iVec).c_str());

        auto bytesProcessed = process_madvise(pidfd, vmasToKernel, iVec, madviseType, 0);

        ATRACE_END();

        if (CC_UNLIKELY(bytesProcessed == -1)) {

            if (errno == EINVAL) {

                // This error is somewhat common due to an unevictable VMA if this is

                // the case silently skip the bad VMA and continue compacting the rest.

                continue;

            } else {

                // Forward irrecoverable errors and bail out compaction

                return -errno;

            }

        }

        totalBytesProcessed += bytesProcessed;

    }

    return totalBytesProcessed;