Android6.0 PackageManagerService dex优化



一、代码

Android6.0 PackageManagerService dex优化是在scanPackageDirtyLI函数中，代码如下：

        if ((scanFlags & SCAN_NO_DEX) == 0) {            int result = mPackageDexOptimizer.performDexOpt(pkg, null /* instruction sets */,                    forceDex, (scanFlags & SCAN_DEFER_DEX) != 0, false /* inclDependencies */,                    (scanFlags & SCAN_BOOTING) == 0);            if (result == PackageDexOptimizer.DEX_OPT_FAILED) {                throw new PackageManagerException(INSTALL_FAILED_DEXOPT, "scanPackageLI");            }        }

主要是调用了PackageDexOptimizer.performDexOpt函数，这个函数又继续调用了performDexOptLI函数

    private int performDexOptLI(PackageParser.Package pkg, String[] targetInstructionSets,            boolean forceDex, boolean defer, boolean bootComplete, ArraySet<String> done) {        final String[] instructionSets = targetInstructionSets != null ?                targetInstructionSets : getAppDexInstructionSets(pkg.applicationInfo);        if (done != null) {            done.add(pkg.packageName);            if (pkg.usesLibraries != null) {//是否有一些共享库的apk也要dex优化                performDexOptLibsLI(pkg.usesLibraries, instructionSets, forceDex, defer,                        bootComplete, done);            }            if (pkg.usesOptionalLibraries != null) {                performDexOptLibsLI(pkg.usesOptionalLibraries, instructionSets, forceDex, defer,                        bootComplete, done);            }        }        if ((pkg.applicationInfo.flags & ApplicationInfo.FLAG_HAS_CODE) == 0) {//没有代码的pkg直接跳过            return DEX_OPT_SKIPPED;        }        final boolean vmSafeMode = (pkg.applicationInfo.flags & ApplicationInfo.FLAG_VM_SAFE_MODE) != 0;        final boolean debuggable = (pkg.applicationInfo.flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0;        final List<String> paths = pkg.getAllCodePathsExcludingResourceOnly();        boolean performedDexOpt = false;        // There are three basic cases here:        // 1.) we need to dexopt, either because we are forced or it is needed        // 2.) we are deferring a needed dexopt        // 3.) we are skipping an unneeded dexopt        final String[] dexCodeInstructionSets = getDexCodeInstructionSets(instructionSets);        for (String dexCodeInstructionSet : dexCodeInstructionSets) {            if (!forceDex && pkg.mDexOptPerformed.contains(dexCodeInstructionSet)) {//没有强制或者已经dex优化过直接continue                continue;            }            for (String path : paths) {//遍历所有代码路径                final int dexoptNeeded;                if (forceDex) {                    dexoptNeeded = DexFile.DEX2OAT_NEEDED;                } else {                    try {                        dexoptNeeded = DexFile.getDexOptNeeded(path, pkg.packageName,                                dexCodeInstructionSet, defer);                    } catch (IOException ioe) {                        Slog.w(TAG, "IOException reading apk: " + path, ioe);                        return DEX_OPT_FAILED;                    }                }                if (!forceDex && defer && dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {                    // We're deciding to defer a needed dexopt. Don't bother dexopting for other                    // paths and instruction sets. We'll deal with them all together when we process                    // our list of deferred dexopts.                    addPackageForDeferredDexopt(pkg);                    return DEX_OPT_DEFERRED;                }                if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {                    final String dexoptType;                    String oatDir = null;                    if (dexoptNeeded == DexFile.DEX2OAT_NEEDED) {                        dexoptType = "dex2oat";//dex-opt类型                        try {                            oatDir = createOatDirIfSupported(pkg, dexCodeInstructionSet);//获取otaDir                        } catch (IOException ioe) {                            Slog.w(TAG, "Unable to create oatDir for package: " + pkg.packageName);                            return DEX_OPT_FAILED;                        }                    } else if (dexoptNeeded == DexFile.PATCHOAT_NEEDED) {                        dexoptType = "patchoat";                    } else if (dexoptNeeded == DexFile.SELF_PATCHOAT_NEEDED) {                        dexoptType = "self patchoat";                    } else {                        throw new IllegalStateException("Invalid dexopt needed: " + dexoptNeeded);                    }                    Log.i(TAG, "Running dexopt (" + dexoptType + ") on: " + path + " pkg="//关键信息打印                            + pkg.applicationInfo.packageName + " isa=" + dexCodeInstructionSet                            + " vmSafeMode=" + vmSafeMode + " debuggable=" + debuggable                            + " oatDir = " + oatDir + " bootComplete=" + bootComplete);                    final int sharedGid = UserHandle.getSharedAppGid(pkg.applicationInfo.uid);                    final int ret = mPackageManagerService.mInstaller.dexopt(path, sharedGid,//调用installd的dexopt                            !pkg.isForwardLocked(), pkg.packageName, dexCodeInstructionSet,                            dexoptNeeded, vmSafeMode, debuggable, oatDir, bootComplete);                    // Dex2oat might fail due to compiler / verifier errors. We soldier on                    // regardless, and attempt to interpret the app as a safety net.                    if (ret == 0) {//Installd dexopt成功了                        performedDexOpt = true;                    }                }            }            // At this point we haven't failed dexopt and we haven't deferred dexopt. We must            // either have either succeeded dexopt, or have had getDexOptNeeded tell us            // it isn't required. We therefore mark that this package doesn't need dexopt unless            // it's forced. performedDexOpt will tell us whether we performed dex-opt or skipped            // it.            pkg.mDexOptPerformed.add(dexCodeInstructionSet);//这代表已经处理过了        }        // If we've gotten here, we're sure that no error occurred and that we haven't        // deferred dex-opt. We've either dex-opted one more paths or instruction sets or        // we've skipped all of them because they are up to date. In both cases this        // package doesn't need dexopt any longer.        return performedDexOpt ? DEX_OPT_PERFORMED : DEX_OPT_SKIPPED;    }

上面这个函数遍历apk所有的代码路径，根据解析得到dexoptType，最后用installd来完成dexopt工作。

其中还有一个当dexoptType为dex2oat时，会调用createOatDirIfSupported来得到oatdir，其他情况oatdir为空了。

createOatDirIfSupported函数也是codePath如果是目录，就用Installd在该目录下创建一个目录，如果是apk文件直接返回空。

    private String createOatDirIfSupported(PackageParser.Package pkg, String dexInstructionSet)            throws IOException {        if (!pkg.canHaveOatDir()) {            return null;        }        File codePath = new File(pkg.codePath);        if (codePath.isDirectory()) {            File oatDir = getOatDir(codePath);            mPackageManagerService.mInstaller.createOatDir(oatDir.getAbsolutePath(),                    dexInstructionSet);            return oatDir.getAbsolutePath();        }        return null;    }

最后我们再来看下Installd的dexopt函数，先会根据oat_dir是否为空，如果不为空判断是否有效，然后也会根据这个oat_dir计算这个out_path，没有oat_dir就会调用create_cache_path函数来计算out_path。

int dexopt(const char *apk_path, uid_t uid, bool is_public,           const char *pkgname, const char *instruction_set, int dexopt_needed,           bool vm_safe_mode, bool debuggable, const char* oat_dir, bool boot_complete){    ......    // Early best-effort check whether we can fit the the path into our buffers.    // Note: the cache path will require an additional 5 bytes for ".swap", but we'll try to run    // without a swap file, if necessary.    if (strlen(apk_path) >= (PKG_PATH_MAX - 8)) {        ALOGE("apk_path too long '%s'\n", apk_path);        return -1;    }    if (oat_dir != NULL && oat_dir[0] != '!') {        if (validate_apk_path(oat_dir)) {            ALOGE("invalid oat_dir '%s'\n", oat_dir);            return -1;        }        if (calculate_oat_file_path(out_path, oat_dir, apk_path, instruction_set)) {            return -1;        }    } else {        if (create_cache_path(out_path, apk_path, instruction_set)) {            return -1;        }    }

calculate_oat_file_path函数就会根据oat_dir等来生成out_path.

int calculate_oat_file_path(char path[PKG_PATH_MAX], const char *oat_dir, const char *apk_path,        const char *instruction_set) {    char *file_name_start;    char *file_name_end;    file_name_start = strrchr(apk_path, '/');    if (file_name_start == NULL) {         ALOGE("apk_path '%s' has no '/'s in it\n", apk_path);        return -1;    }    file_name_end = strrchr(apk_path, '.');    if (file_name_end < file_name_start) {        ALOGE("apk_path '%s' has no extension\n", apk_path);        return -1;    }    // Calculate file_name    int file_name_len = file_name_end - file_name_start - 1;    char file_name[file_name_len + 1];    memcpy(file_name, file_name_start + 1, file_name_len);    file_name[file_name_len] = '\0';    // <apk_parent_dir>/oat/<isa>/<file_name>.odex    snprintf(path, PKG_PATH_MAX, "%s/%s/%s.odex", oat_dir, instruction_set, file_name);    return 0;}

没有oat_dir就会调用create_cache_path函数来计算out_path,最后会在DALVIK_CACHE_PREFIX目录下创建，而这个目录就是/data/dalvik-cache/，也就是最终会在这个目录下生成dex文件。

int create_cache_path(char path[PKG_PATH_MAX], const char *src, const char *instruction_set){    char *tmp;    int srclen;    int dstlen;    srclen = strlen(src);        /* demand that we are an absolute path */    if ((src == 0) || (src[0] != '/') || strstr(src,"..")) {        return -1;    }    if (srclen > PKG_PATH_MAX) {        // XXX: PKG_NAME_MAX?        return -1;    }    dstlen = srclen + strlen(DALVIK_CACHE_PREFIX) +        strlen(instruction_set) +        strlen(DALVIK_CACHE_POSTFIX) + 2;    if (dstlen > PKG_PATH_MAX) {        return -1;    }    sprintf(path,"%s%s/%s%s",            DALVIK_CACHE_PREFIX,            instruction_set,            src + 1, /* skip the leading / */            DALVIK_CACHE_POSTFIX);    for(tmp = path + strlen(DALVIK_CACHE_PREFIX) + strlen(instruction_set) + 1; *tmp; tmp++) {        if (*tmp == '/') {            *tmp = '@';        }    }    return 0;}

继续分析dexopt函数，根据dexopt类型来看源文件，一般是apk文件

    switch (dexopt_needed) {        case DEXOPT_DEX2OAT_NEEDED:            input_file = apk_path;            break;        case DEXOPT_PATCHOAT_NEEDED:            if (!calculate_odex_file_path(in_odex_path, apk_path, instruction_set)) {                return -1;            }            input_file = in_odex_path;            break;        case DEXOPT_SELF_PATCHOAT_NEEDED:            input_file = out_path;            break;        default:            ALOGE("Invalid dexopt needed: %d\n", dexopt_needed);            exit(72);    }

后面就是打开文件，然后fork进程，调用run_dex2oat函数来执行。我们就不分析了

二、实例

2.1 没有目录

最终如果你的apk没有目录，会在如下目录有classes.dex后缀的文件。

root@lc1861evb_arm64:/data/dalvik-cache/arm # lsdata@[e-mail]@classes.dexdata@[e-mail]@classes.dex

2.2 有目录

而有目录的，比如我们自己安装的墨迹天气，会有一个oat目录，最后有一个base.odex文件

root@lc1861evb_arm64:/data/app/com.moji.mjweather-1/oat/arm # lsbase.odex