Merge "Make per-application memcg hierarchy configurable via a property" into pi-dev

#include <android-base/file.h>

#include <android-base/logging.h>

#ifdef __ANDROID__

#include <android-base/properties.h>

#endif

#include <android-base/stringprintf.h>

#include <android-base/strings.h>

#include <private/android_filesystem_config.h>

#include <processgroup/processgroup.h>

#ifdef __ANDROID__

using android::base::GetBoolProperty;

#endif

using android::base::StartsWith;

using android::base::StringPrintf;

using android::base::WriteStringToFile;

static const std::string& GetCgroupRootPath() {

    static std::string cgroup_root_path;

    std::call_once(init_path_flag, [&]() {

            // Check if mem cgroup is mounted, only then check for write-access to avoid

            // SELinux denials

#ifdef __ANDROID__

        // low-ram devices use per-app memcg by default, unlike high-end ones

        bool low_ram_device = GetBoolProperty("ro.config.low_ram", false);

        bool per_app_memcg =

            GetBoolProperty("ro.config.per_app_memcg", low_ram_device);

#else

        // host does not support Android properties

        bool per_app_memcg = false;

#endif

        if (per_app_memcg) {

            // Check if mem cgroup is mounted, only then check for

            // write-access to avoid SELinux denials

            cgroup_root_path =

                (access(MEM_CGROUP_TASKS, F_OK) || access(MEM_CGROUP_PATH, W_OK) ? ACCT_CGROUP_PATH

                                                                                 : MEM_CGROUP_PATH);

                (access(MEM_CGROUP_TASKS, F_OK) || access(MEM_CGROUP_PATH, W_OK) ?

                ACCT_CGROUP_PATH : MEM_CGROUP_PATH);

        } else {

            cgroup_root_path = ACCT_CGROUP_PATH;

        }

    });

    return cgroup_root_path;

}