libpsi: initial revision

New library to create, register and destroy PSI monitors in a consistent
way with lmkd.

Test: used within lmkd
Bug: 111308141
Change-Id: If243a97f178e90fe41e2de90c7b858ba82440279
Signed-off-by: Suren Baghdasaryan <surenb@google.com>

lmkd/libpsi/Android.bp

@@ -0,0 +1,22 @@
+cc_library_headers {
+    name: "libpsi_headers",
+    export_include_dirs: ["include"],
+}
+
+cc_library {
+    name: "libpsi",
+    srcs: ["psi.c"],
+    shared_libs: [
+        "liblog"
+    ],
+    header_libs: [
+        "libpsi_headers",
+    ],
+    export_header_lib_headers: [
+        "libpsi_headers",
+    ],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+}

lmkd/libpsi/OWNERS

@@ -0,0 +1 @@
+surenb@google.com

lmkd/libpsi/include/psi/psi.h

@@ -0,0 +1,68 @@
+/*
+ * 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
+ *
+ *      http://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.
+ */
+
+#ifndef __ANDROID_PSI_H__
+#define __ANDROID_PSI_H__
+
+#include <sys/cdefs.h>
+#include <sys/types.h>
+
+__BEGIN_DECLS
+
+enum psi_stall_type {
+    PSI_SOME,
+    PSI_FULL,
+    PSI_TYPE_COUNT
+};
+
+/*
+ * Initializes psi monitor.
+ * stall_type, threshold_us and window_us are monitor parameters
+ * When successful, the function returns file descriptor that can
+ * be used with poll/epoll syscalls to wait for EPOLLPRI events.
+ * When unsuccessful, the function returns -1 and errno is set
+ * appropriately.
+ */
+int init_psi_monitor(enum psi_stall_type stall_type,
+        int threshold_us, int window_us);
+
+/*
+ * Registers psi monitor file descriptor fd on the epoll instance
+ * referred to by the file descriptor epollfd.
+ * data parameter will be associated with event's epoll_data.ptr
+ * member.
+ */
+int register_psi_monitor(int epollfd, int fd, void* data);
+
+/*
+ * Unregisters psi monitor file descriptor fd from the epoll instance
+ * referred to by the file descriptor epollfd.
+ */
+int unregister_psi_monitor(int epollfd, int fd);
+
+/*
+ * Destroys psi monitor.
+ * fd is the file descriptor returned by psi monitor initialization
+ * routine.
+ * Note that if user process exits without calling this routine
+ * kernel will destroy the monitor as its lifetime is linked to
+ * the file descriptor.
+ */
+void destroy_psi_monitor(int fd);
+
+__END_DECLS
+
+#endif  // __ANDROID_PSI_H__

lmkd/libpsi/psi.c

@@ -0,0 +1,99 @@
+/*
+ * 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
+ *
+ *      http://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.
+ */
+
+#define LOG_TAG "libpsi"
+
+#include <errno.h>
+#include <string.h>
+#include <sys/epoll.h>
+
+#include <log/log.h>
+#include "psi/psi.h"
+
+#define PSI_MON_FILE_MEMORY "/proc/pressure/memory"
+
+static const char* stall_type_name[] = {
+        "some",
+        "full",
+};
+
+int init_psi_monitor(enum psi_stall_type stall_type,
+             int threshold_us, int window_us) {
+    int fd;
+    int res;
+    char buf[256];
+
+    fd = TEMP_FAILURE_RETRY(open(PSI_MON_FILE_MEMORY, O_WRONLY | O_CLOEXEC));
+    if (fd < 0) {
+        ALOGE("No kernel psi monitor support (errno=%d)", errno);
+        return -1;
+    }
+
+    switch (stall_type) {
+    case (PSI_SOME):
+    case (PSI_FULL):
+        res = snprintf(buf, sizeof(buf), "%s %d %d",
+            stall_type_name[stall_type], threshold_us, window_us);
+        break;
+    default:
+        ALOGE("Invalid psi stall type: %d", stall_type);
+        errno = EINVAL;
+        goto err;
+    }
+
+    if (res >= (ssize_t)sizeof(buf)) {
+        ALOGE("%s line overflow for psi stall type '%s'",
+            PSI_MON_FILE_MEMORY, stall_type_name[stall_type]);
+        errno = EINVAL;
+        goto err;
+    }
+
+    res = TEMP_FAILURE_RETRY(write(fd, buf, strlen(buf) + 1));
+    if (res < 0) {
+        ALOGE("%s write failed for psi stall type '%s'; errno=%d",
+            PSI_MON_FILE_MEMORY, stall_type_name[stall_type], errno);
+        goto err;
+    }
+
+    return fd;
+
+err:
+    close(fd);
+    return -1;
+}
+
+int register_psi_monitor(int epollfd, int fd, void* data) {
+    int res;
+    struct epoll_event epev;
+
+    epev.events = EPOLLPRI;
+    epev.data.ptr = data;
+    res = epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &epev);
+    if (res < 0) {
+        ALOGE("epoll_ctl for psi monitor failed; errno=%d", errno);
+    }
+    return res;
+}
+
+int unregister_psi_monitor(int epollfd, int fd) {
+    return epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, NULL);
+}
+
+void destroy_psi_monitor(int fd) {
+    if (fd >= 0) {
+        close(fd);
+    }
+}