blob: 1626e7ec50b9592fc33a6ff3cda17341ce342f48 [file] [log] [blame]
/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* rss_hwm_reset clears the RSS high-water mark counters for all currently
* running processes. It writes "5" to /proc/PID/clear_refs for every PID.
*
* It runs in its own process becuase dac_override capability is required
* in order to write to other processes' clear_refs.
*
* It is invoked from a system service by flipping sys.rss_hwm_reset.on
* property to "1".
*/
#define LOG_TAG "rss_hwm_reset"
#include <dirent.h>
#include <string>
#include <android-base/file.h>
#include <android-base/stringprintf.h>
#include <log/log.h>
namespace {
// Resets RSS HWM counter for the selected process by writing 5 to
// /proc/PID/clear_refs.
void reset_rss_hwm(const char* pid) {
std::string clear_refs_path =
::android::base::StringPrintf("/proc/%s/clear_refs", pid);
::android::base::WriteStringToFile("5", clear_refs_path);
}
}
// Clears RSS HWM counters for all currently running processes.
int main(int /* argc */, char** /* argv[] */) {
DIR* dirp = opendir("/proc");
if (dirp == nullptr) {
ALOGE("unable to read /proc");
return 1;
}
struct dirent* entry;
while ((entry = readdir(dirp)) != nullptr) {
// Skip entries that are not directories.
if (entry->d_type != DT_DIR) continue;
// Skip entries that do not contain only numbers.
const char* pid = entry->d_name;
while (*pid) {
if (*pid < '0' || *pid > '9') break;
pid++;
}
if (*pid != 0) continue;
pid = entry->d_name;
reset_rss_hwm(pid);
}
closedir(dirp);
return 0;
}