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What are the reasons for lag in-game
Posted: 25 Feb 2014, 14:55
by Speiros02
I'm aware that this is an ongoing problem, and might not be specific to my system, but I would like to get some ideas...as many as possible actually...as to what is causing the lag in-game. This would be great to see an exhaustive list as such, and then maybe AFTER that, a new post on how each one can be addressed...
So, what do YOU know of that causes lag in-game?
Re: What are the reasons for lag in-game
Posted: 25 Feb 2014, 16:02
by o11c
There are a number of reasons, but it usually comes down to "your internet is crap":
- You're on wifi.
- Your ISP is dropping packets. This is especially a problem in parts of Europe, which due to business politics, has terrible backbone routing even though end-user internet connections have higher bandwidth than the US. This can sometimes be fixed by making your own tunnel, but I don't know where to put it.
- The DDoS-resistant datacenter we're in might be fighting off an attack against a bigger target in the same datacenter.
- Occasionally there may be spikes due to server load. I *think* I have fixed all of these.
Re: What are the reasons for lag in-game
Posted: 25 Feb 2014, 16:19
by Speiros02
o11c wrote:There are a number of reasons, but it usually comes down to "your internet is crap":
- You're on wifi.
- Your ISP is dropping packets. This is especially a problem in parts of Europe, which due to business politics, has terrible backbone routing even though end-user internet connections have higher bandwidth than the US. This can sometimes be fixed by making your own tunnel, but I don't know where to put it.
- The DDoS-resistant datacenter we're in might be fighting off an attack against a bigger target in the same datacenter.
- Occasionally there may be spikes due to server load. I *think* I have fixed all of these.
lol, well I can't argue about my internet being crap...Australia is certainly behind the rest of the world in internet, due to the distance from other continents, and the small population. It's also hell expensive. Thanks for the points.
Re: What are the reasons for lag in-game
Posted: 18 Mar 2014, 19:55
by Hello=)
Ahh, people. You can use traceroute, mtr or similar tools to get idea where packet loss/delay happens and measure it in technical ways, which would allow to distinguish "wireless crap" and other cases. Internet is complicated thing where many things can fall apart. Failure of any part of quite lengthy chain would make you unhappy. Use proper tools to get idea what wrong and troubleshoot it (if you can). If packets are lost or delayed on your area - your fault. If on ISP area - their fault. Some intermediate routers? Good luck to explain their owners it suxx, when you're not their customer, etc
.
Re: What are the reasons for lag in-game
Posted: 19 Mar 2014, 15:21
by Nard
I also still have lags while I have a somewhat good average ping (160-210ms). They occur mostly when number of players gets over (about) 45. They can be repeated small lags (( less or about a second, with period of a few seconds), or spikes of several seconds ("rare").
Re: What are the reasons for lag in-game
Posted: 19 Mar 2014, 15:36
by veryape
I havn't actually noticed network lags, but sometimes when i run to the GY alone it feels like it takes some time for the mobs to spawn. So i run there, see that there are no mobs in the initial part of the gy. I continue on in searching for the people i think have cleared them and end up in the middle of all the spawns and die.
Other than that I havn't had any kind of lag problems have happened often enough for me to think that it has to do with the server/location of the server.
Re: What are the reasons for lag in-game
Posted: 19 Mar 2014, 15:57
by Chay
veryape wrote:but sometimes when i run to the GY alone it feels like it takes some time for the mobs to spawn. So i run there, see that there are no mobs in the initial part of the gy. I continue on in searching for the people i think have cleared them and end up in the middle of all the spawns and die.
that's not lag, the mobs are killed only every xy seconds via a fixed timer, the spawn you see is just the usual (fixed timed) respawn after mob exitus, not triggered by anyone entering the map . (
so in fact if you stay dead on the gy you can also see skels rise from the death and soon crumble to dust again
Re: What are the reasons for lag in-game
Posted: 19 Mar 2014, 19:23
by Nard
veryape wrote:I havn't actually noticed network lags,
Indeed, The lags I am speaking about have nothing to do with network. (nor my vido settings or any kind of computer overload from my side. I checked with only manaplus lanched, and also with different computers an OSes)
Re: What are the reasons for lag in-game
Posted: 19 Mar 2014, 19:55
by AnonDuck
Nard wrote:I also still have lags while I have a somewhat good average ping (160-210ms). They occur mostly when number of players gets over (about) 45. They can be repeated small lags (( less or about a second, with period of a few seconds), or spikes of several seconds ("rare").
The occasional lost TCP packet will do that. When TCP loses a packet the stream has to recover. TMW uses fast-recovery TCP options to make this happen as quickly as possible but it can still take some time to recover and lead to instability of the stream for a small time afterwards. "Peak internet usage" hours could easily explain the relation to online players and packet loss. The output of netstat -s corroborates this hypothesis There are many TCP recoveries happening and Quick-Ack mode is activated quite often:
Another possibility is that the server is overloaded or stalling. Judging by the CPU load on the server it doesn't look like there is any sort of bottleneck in processing power. The map-server may be stalling somehow without using much CPU. There is no insturmentation in place to determine if this is happening. Knowing the code-base and o11c's attention to detail (and simply watching the machine carefully with an experienced eye) this possibility seems more unlikely to me than the first.
Re: What are the reasons for lag in-game
Posted: 19 Mar 2014, 20:07
by o11c
There *used* to be a bit of server code that stuck the process in D state every 1024 seconds, I changed it to fork so it could execute asynchronously.
There might still be a tiny delay, but I don't expect it to be visible. That said, I do still have plans to fix it by switching to syslog.
Re: What are the reasons for lag in-game
Posted: 20 Mar 2014, 06:41
by Nard
MadCamel wrote:The occasional lost TCP packet will do that. When TCP loses a packet the stream has to recover.[...]
Another possibility is that the server is overloaded or stalling. Judging by the CPU load on the server it doesn't look like there is any sort of bottleneck in processing power. The map-server may be stalling somehow without using much CPU. There is no insturmentation in place to determine if this is happening. Knowing the code-base and o11c's attention to detail (and simply watching the machine carefully with an experienced eye) this possibility seems more unlikely to me than the first.
On several occasions, I tried to find correlations betwen the "lags" I observed, manaplus ping and netstat logs (various time intervals). Unfortunately the "measures" were not precise and synced enough to show anything more than the most obvious ones, which were network related.
Packet loss probably occur in the following issue that I should have reported again along with lags: After disconnecting an account, it happens that the server does not receive the message and the char stays online. It can stay online
several hours, the maximum i could see at the moment is about 12h, until I reconnect. I should perhaps call that client-server misunderstanding instead of packet loss.
In the same order of ideas, The mobs ghosting have "recently" been significantly reduced (I sincerely can't say when it occured).
About bottlenecks: It may be the time to test again playing configurations where it was known that they caused lags (Illia for example, before V0id made the "exploit" mod).
If they still occur, It might be interesting to develop instruments on both client and server sides, but it would require to define properly what we call a lag and which points to look at.
@o11c: I never noticed (nor heard about from players) anything like about 20mn periodic. The time period is long enough though so we can have missed it. Glad to know that this issue is fixed anyway. Thank you.
Re: What are the reasons for lag in-game
Posted: 03 May 2014, 07:48
by Deimheucadh
here is my tracert output:
Yekaterinburg - Moscow - Poland - Stockholm - Frankfurt - Duesseldorf - Paris - Washington - Houston
200 ms each hip. what do you think, do i feel lags?
Re: What are the reasons for lag in-game
Posted: 03 May 2014, 17:15
by o11c
Deimheucadh wrote:here is my tracert output:
Yekaterinburg - Moscow - Poland - Stockholm - Frankfurt - Duesseldorf - Paris - Washington - Houston
200 ms each hip. what do you think, do i feel lags?
The 200 ms is a total, and 200 ms go get to the other side of the world is as good as you can get.
The troubling thing is your hop 2, which shows an average of 260 ms and a max of 411 ms, so you're losing over 50% of your packets there.