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Commit 2cf55995 authored by Christopher Ferris's avatar Christopher Ferris
Browse files

Decrease size of LogBufferElements to 32 bytes. 

- Remove virtual from the destructor.
- Remove mTag and derive it when calling getTag().
- Add a boolean mDropped to tell when a message is dropped.
- When dropping a message, and it contains valid tag data, reallocate
  the message to only contain the tag data.
- Add the packed tag to the class.

This saves about ~150K of PSS on a typical log stream since it moves the
size of the LogBufferElement from 48 bytes to 32 bytes which puts it in
a smaller bin.

Bug: 63792187

Test: Builds, unit tests pass.
Change-Id: Ia5afce343ea3d344fcecd78c648338e94f5c9312
(cherry picked from commit 74e74f96)
parent f7ad6222

logd/LogBufferElement.cpp

+36 −12
Original line number Diff line number Diff line
@@ -41,22 +41,20 @@ LogBufferElement::LogBufferElement(log_id_t log_id, log_time realtime, 
      mTid(tid),

      mRealTime(realtime),

      mMsgLen(len),

      mLogId(log_id) {

      mLogId(log_id),

      mDropped(false) {

    mMsg = new char[len];

    memcpy(mMsg, msg, len);

    mTag = (isBinary() && (mMsgLen >= sizeof(uint32_t)))

               ? le32toh(reinterpret_cast<android_event_header_t*>(mMsg)->tag)

               : 0;

}



LogBufferElement::LogBufferElement(const LogBufferElement& elem)

    : mTag(elem.mTag),

      mUid(elem.mUid),

    : mUid(elem.mUid),

      mPid(elem.mPid),

      mTid(elem.mTid),

      mRealTime(elem.mRealTime),

      mMsgLen(elem.mMsgLen),

      mLogId(elem.mLogId) {

      mLogId(elem.mLogId),

      mDropped(elem.mDropped) {

    mMsg = new char[mMsgLen];

    memcpy(mMsg, elem.mMsg, mMsgLen);

}
@@ -65,6 +63,32 @@ LogBufferElement::~LogBufferElement() { 
    delete[] mMsg;

}



uint32_t LogBufferElement::getTag() const {

    return (isBinary() &&

            ((mDropped && mMsg != nullptr) ||

             (!mDropped && mMsgLen >= sizeof(android_event_header_t))))

               ? reinterpret_cast<const android_event_header_t*>(mMsg)->tag

               : 0;

}



unsigned short LogBufferElement::setDropped(unsigned short value) {

    // The tag information is saved in mMsg data, if the tag is non-zero

    // save only the information needed to get the tag.

    if (getTag() != 0) {

        if (mMsgLen > sizeof(android_event_header_t)) {

            char* truncated_msg = new char[sizeof(android_event_header_t)];

            memcpy(truncated_msg, mMsg, sizeof(android_event_header_t));

            delete[] mMsg;

            mMsg = truncated_msg;

        }  // mMsgLen == sizeof(android_event_header_t), already at minimum.

    } else {

        delete[] mMsg;

        mMsg = nullptr;

    }

    mDropped = true;

    return mDroppedCount = value;

}



// caller must own and free character string

char* android::tidToName(pid_t tid) {

    char* retval = NULL;
@@ -164,8 +188,8 @@ size_t LogBufferElement::populateDroppedMessage(char*& buffer, LogBuffer* parent 
    // identical to below to calculate the buffer size required

    const char* type = lastSame ? "identical" : "expire";

    size_t len = snprintf(NULL, 0, format_uid, mUid, name ? name : "",

                          commName ? commName : "", type, mDropped,

                          (mDropped > 1) ? "s" : "");

                          commName ? commName : "", type, getDropped(),

                          (getDropped() > 1) ? "s" : "");



    size_t hdrLen;

    if (isBinary()) {
@@ -196,8 +220,8 @@ size_t LogBufferElement::populateDroppedMessage(char*& buffer, LogBuffer* parent 
    }



    snprintf(buffer + hdrLen, len + 1, format_uid, mUid, name ? name : "",

             commName ? commName : "", type, mDropped,

             (mDropped > 1) ? "s" : "");

             commName ? commName : "", type, getDropped(),

             (getDropped() > 1) ? "s" : "");

    free(const_cast<char*>(name));

    free(const_cast<char*>(commName));
@@ -225,7 +249,7 @@ log_time LogBufferElement::flushTo(SocketClient* reader, LogBuffer* parent, 


    char* buffer = NULL;



    if (!mMsg) {

    if (mDropped) {

        entry.len = populateDroppedMessage(buffer, parent, lastSame);

        if (!entry.len) return mRealTime;

        iovec[1].iov_base = buffer;

logd/LogBufferElement.h

+11 −19
Original line number Diff line number Diff line
@@ -32,25 +32,25 @@ class LogBuffer; 
                                  // chatty for the temporal expire messages

#define EXPIRE_RATELIMIT 10  // maximum rate in seconds to report expiration



class LogBufferElement {

class __attribute__((packed)) LogBufferElement {

    friend LogBuffer;



    // sized to match reality of incoming log packets

    uint32_t mTag;  // only valid for isBinary()

    const uint32_t mUid;

    const uint32_t mPid;

    const uint32_t mTid;

    log_time mRealTime;

    char* mMsg;

    union {

        const uint16_t mMsgLen;  // mMSg != NULL

        uint16_t mDropped;       // mMsg == NULL

        const uint16_t mMsgLen;  // mDropped == false

        uint16_t mDroppedCount;  // mDropped == true

    };

    const uint8_t mLogId;

    bool mDropped;



    static atomic_int_fast64_t sequence;



    // assumption: mMsg == NULL

    // assumption: mDropped == true

    size_t populateDroppedMessage(char*& buffer, LogBuffer* parent,

                                  bool lastSame);
@@ -58,7 +58,7 @@ class LogBufferElement { 
    LogBufferElement(log_id_t log_id, log_time realtime, uid_t uid, pid_t pid,

                     pid_t tid, const char* msg, unsigned short len);

    LogBufferElement(const LogBufferElement& elem);

    virtual ~LogBufferElement();

    ~LogBufferElement();



    bool isBinary(void) const {

        return (mLogId == LOG_ID_EVENTS) || (mLogId == LOG_ID_SECURITY);
@@ -76,24 +76,16 @@ class LogBufferElement { 
    pid_t getTid(void) const {

        return mTid;

    }

    uint32_t getTag() const {

        return mTag;

    }

    uint32_t getTag() const;

    unsigned short getDropped(void) const {

        return mMsg ? 0 : mDropped;

    }

    unsigned short setDropped(unsigned short value) {

        if (mMsg) {

            delete[] mMsg;

            mMsg = NULL;

        }

        return mDropped = value;

        return mDropped ? mDroppedCount : 0;

    }

    unsigned short setDropped(unsigned short value);

    unsigned short getMsgLen() const {

        return mMsg ? mMsgLen : 0;

        return mDropped ? 0 : mMsgLen;

    }

    const char* getMsg() const {

        return mMsg;

        return mDropped ? nullptr : mMsg;

    }

    log_time getRealTime(void) const {

        return mRealTime;