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Commit ed3bbc3a authored by Steve Kondik's avatar Steve Kondik
Browse files

core: Reduce mutex contention in ActivityManager 

 * applyOomAdjLocked in ActivityManager will call into native
   layer to adjust tasks in the cpuctl and memory cgroups. The global AM
   lock is held while this happens, and on a busy system can result in
   slowdowns.
 * The cpuctl cgroup is already handled in a sane way. Adjust the memory
   cgroup code to cache file descriptors to reduce overhead by an order
   of magnitude.
 * These cgroups are actually exactly the same in their content, in the
   future when remounting a cgroup fs is supported we can combine them.

Change-Id: If0043e651eebdf73075a96e6de618badd8b5935b
parent b09f7797

core/jni/android_util_Process.cpp

+25 −12
Original line number Diff line number Diff line
@@ -370,27 +370,40 @@ jint android_os_Process_getThreadPriority(JNIEnv* env, jobject clazz, 
    return pri;

}



static bool memcgSupported = false;

static int memcgTasksFd = -1;

static int memcgSwapTasksFd = -1;

static pthread_once_t memcgInitOnce = PTHREAD_ONCE_INIT;



static void memcgInit(void) {

    if (!access("/sys/fs/cgroup/memory/tasks", F_OK)) {

        memcgTasksFd = open("/sys/fs/cgroup/memory/tasks", O_WRONLY);

        if (memcgTasksFd < 0) {

            return;

        }

        memcgSwapTasksFd = open("/sys/fs/cgroup/memory/sw/tasks", O_WRONLY);

        if (memcgSwapTasksFd < 0) {

            close(memcgTasksFd);

            return;

        }

        memcgSupported = true;

    }

}



jboolean android_os_Process_setSwappiness(JNIEnv *env, jobject clazz,

                                          jint pid, jboolean is_increased)

{

    char text[64];



    if (is_increased) {

        strcpy(text, "/sys/fs/cgroup/memory/sw/tasks");

    } else {

        strcpy(text, "/sys/fs/cgroup/memory/tasks");

    }



    struct stat st;

    if (stat(text, &st) || !S_ISREG(st.st_mode)) {

    pthread_once(&memcgInitOnce, memcgInit);

    if (!memcgSupported) {

        return false;

    }



    int fd = open(text, O_WRONLY);

    int fd = is_increased ? memcgSwapTasksFd : memcgTasksFd;

    char text[64];



    if (fd >= 0) {

        sprintf(text, "%" PRId32, pid);

        write(fd, text, strlen(text));

        close(fd);

    }



    return true;