Me and my friend are making a node.js game, and we have been testing cpu, but after profiling this process called zlib is sucking most of the CPU/RAM

3 clients connected to a game is fine, but when 12~13 players are connected it uses 58% where zlib is using about 30% of this cpu.

inclusive      self           name
ticks   total  ticks   total
64775   58.5%  64775   58.5%  /lib/x86_64-linux-gnu/libc-2.19.so
25001   22.6%    224    0.2%  LazyCompile: *callback zlib.js:409
//this one is a different zlib
7435    6.7%     82    0.1%  LazyCompile: ~callback zlib.js:409

Is there any way to decrease the cpu usage from this? or is there a reason why it is increasing so much.

I have done some reading and I am told it is from socket.io so here is our section of socket sending most of the data.

for (var i = 0; i < users.length; i++) {
    if (u.room == users[i].room && users[i].x + users[i].radius >= u.x - u.screenWidth / 2 - 20 && users[i].x - users[i].radius <= u.x + u.screenWidth / 2 + 20 && users[i].y + users[i].radius >= u.y - u.screenHeight / 2 - 20 && users[i].y - users[i].radius <= u.y + u.screenHeight / 2 + 20) {
        if (users[i].id == u.id) {
            visiblePlayers.push({
                x: users[i].x,
                y: users[i].y,
                angle: users[i].angle,
                hue: users[i].hue,
                radius: users[i].radius,
                squeeze: users[i].squeeze,
                name: users[i].name,
                dead: users[i].dead,
                isPlayer: true,
                kills: users[i].kills
            });
        } else {
            visiblePlayers.push({
                x: users[i].x,
                y: users[i].y,
                angle: users[i].angle,
                hue: users[i].hue,
                radius: users[i].radius,
                squeeze: users[i].squeeze,
                name: users[i].name,
                dead: users[i].dead
            });
        }
        // SEND DYING INFO: (FOR OFFLINE ANIMATION):
        if (users[i].dying) {
            visiblePlayers[visiblePlayers.length - 1].dying = true;
        }
    }
}
var visibleEnergy = [];
for (var i = 0; i < energies.length; i++) {
    if (u.firstSend || (energies[i].updated && energies[i].room == u.room)) {
        var anim = energies[i].animate;
        if (u.firstSend)
            anim = true;
        visibleEnergy.push({
            x: energies[i].x,
            y: energies[i].y,
            radius: energies[i].radius,
            index: i,
            animate: anim,
            hue: energies[i].hue,
            room: energies[i].room
        });
    }
}

// SEND PLAYER UPDATES TO CLIENTS:
sockets[u.id].emit('serverTellPlayerMove', visiblePlayers,
    visibleEnergy);

Zlib is one of out problems, but also if there are any other optimisation methods to decrease server CPU Thanks.

My friend and I are making a node.js game, and we have been testing CPU. After profiling, it was determined that this process called zlib is sucking most of the CPU/RAM.

3 clients connected to a game is fine, but when 12~13 players are connected it uses 58% where zlib is using about 30% of this CPU.

inclusive      self           name
ticks   total  ticks   total
64775   58.5%  64775   58.5%  /lib/x86_64-linux-gnu/libc-2.19.so
25001   22.6%    224    0.2%  LazyCompile: *callback zlib.js:409
//this one is a different zlib
7435    6.7%     82    0.1%  LazyCompile: ~callback zlib.js:409

Is there any way to decrease the CPU usage from this? Or is there a reason why it is increasing so much?

I have done some reading and I am told it is from socket.io, so here is our section of socket sending most of the data:

for (var i = 0; i < users.length; i++) {
    if (u.room == users[i].room && users[i].x + users[i].radius >= u.x - u.screenWidth / 2 - 20 && users[i].x - users[i].radius <= u.x + u.screenWidth / 2 + 20 && users[i].y + users[i].radius >= u.y - u.screenHeight / 2 - 20 && users[i].y - users[i].radius <= u.y + u.screenHeight / 2 + 20) {
        if (users[i].id == u.id) {
            visiblePlayers.push({
                x: users[i].x,
                y: users[i].y,
                angle: users[i].angle,
                hue: users[i].hue,
                radius: users[i].radius,
                squeeze: users[i].squeeze,
                name: users[i].name,
                dead: users[i].dead,
                isPlayer: true,
                kills: users[i].kills
            });
        } else {
            visiblePlayers.push({
                x: users[i].x,
                y: users[i].y,
                angle: users[i].angle,
                hue: users[i].hue,
                radius: users[i].radius,
                squeeze: users[i].squeeze,
                name: users[i].name,
                dead: users[i].dead
            });
        }
        // SEND DYING INFO: (FOR OFFLINE ANIMATION):
        if (users[i].dying) {
            visiblePlayers[visiblePlayers.length - 1].dying = true;
        }
    }
}
var visibleEnergy = [];
for (var i = 0; i < energies.length; i++) {
    if (u.firstSend || (energies[i].updated && energies[i].room == u.room)) {
        var anim = energies[i].animate;
        if (u.firstSend)
            anim = true;
        visibleEnergy.push({
            x: energies[i].x,
            y: energies[i].y,
            radius: energies[i].radius,
            index: i,
            animate: anim,
            hue: energies[i].hue,
            room: energies[i].room
        });
    }
}

// SEND PLAYER UPDATES TO CLIENTS:
sockets[u.id].emit('serverTellPlayerMove', visiblePlayers,
    visibleEnergy);