Can megaprims cause sim lag? (Tme Dilation) - Or anything else?

On the sim where I currently live a guy appears to be building a (sort of) copy of some new york skyscrapers on a platform at about 3200 metres in the sky.

The skyscrapers themselves are just over 100 metres tall (at the tallest) and he appears to still be working on it (adding more when I checked today)

The sim I'm on this morning had no Avatars on it (apart from me) but a few shops below on the ground (again some tall ones using a few Megaprims)

But to be honest, not a LOT of things on the Sim compared to many I've seen (like when you get LOTS of houses all full of stuff/scripts running.)

The TimeDilation (for no reason I can tell) seems to wander between 0.99 and 0.50 ish.

Normally in the 0.80 to 0.99 ish range but as I walk about it just drops to 0.5 ish, for a second then pop back up to 0.8, 0.9 for a few more seconds, then back to 0.6, 0.7 then back to 0.9 again.... As so it goes on.

I can get some screen grabs later of my statistics window, but I'm just wondering why this should be happening and what I could look for to perhaps suggest to the sim owner to look at?

I had the other box (can't remember it's name) the one with the 3 green lights that change colour and in time with my lag when walking I had warnings about long ping times and also sim FPS going below 20.

My client side seems fine (green light)

Apart from Megaprims, is there anything else obvious I could look around for? (see if I spot anything obvious) that would cause this on a sim with only 1 or 2 avatars on it.

This is on Mainland by the way.

I use quite a few megaprims and the sim stats don't show anything like you've described. Dipping low briefly sounds like it is caused by a script. If the dip is at around 1 minute intervals, then it sounds like a temp rezzer script. You can check if it's a temp rezzer by watching the number of prims in the sim. If they go up briefly every minute or so, then there will almost certainly be a temp rezzer there. More than one temp rezzer would cause more spikes in the number of prims, of course.

Oh, right. Do I assume the statistics window shows me that (I'm not at MY pc right now, so can't check)

But no, the Time Dilation number is not dropping like once a minute or something like that. It's in constant flow up and down all the time.

Every second it may change 0.99 , 0.95, 0.65, 0.80, 0.50, 0.60, 0.85, 0.98, 0.98, 0.95, 0.75, 0.60

It could go all thru that range in like 10 to 15 seconds.

I can't really "feel" a pattern to is as of yet. Only that it can vary between 0.50 and 0.99 a few times during 1 minute.

the old walking normally, then walking without moving much, then jump forwards quite a bit as it catches up with itself. that kinda thing.

Yes it does show you that. The "Objects" stat is actually prims.

From those numbers, it could be heavy scripts. It could even be caused by another sim that's using the same CPU. If you have access to live support, perhaps you could get a Linden to have a look.

[added]
If several temp rezzers are being used, they won't operate at the same time, so you would get more dips in the space of minute. Check the prims anyway. I'll explain why...

Temp rezzers that are used to keep objects rezzed without adding to the prim usage, re-rezz the objects every minute - a few seconds before the previous rezzed set of temporary objects are due to be cleaned up (deleted) by SL's system. For those few seconds, twice the number of prims that a temp rezzer rezzes are rezzed, and the prim count goes up accordingly. So if someone has a number of temp rezzers operating, increases in prims will occur much more frequently than at 1 minute intervals.

It's something you can check, anyway.

megaprims can cause anomalies if they are not set phantom or (possibly) are sculpted. I saw dramatic changes in performance when i would rez then derez my 100m megaprim icebergs.
the sculpted bit i am not sure about, but large, nonphantom megas have historically played hell with havok. unless havok4 overcame this... i havent played with megas in a while.

The Anomalies you are refering to were only pre Havok 4. Havok 4 solved all issues related to mega prims.

So in answer to the OP. No, the only issues that remain with Mega Prims are the publics fear of them.

We use quite a few Megas in BSG47, wich relies heavily on physics because of the fighter combat, among many other things. We have not encountered any problems with them.

I'd suggest looking a little deeper into those sim statistics and reporting back. TBH, the kind of behavior you're describing sounds on the surface like physics, which these days is unlikely to be megaprims, and more likely to be somebody's scripted physical pet wandering around. But it may not be physics at all. You can look at the details and see what kind of activity the sim is using during the frames, and even kind of graph them over a short interval to see which components track the time dilation.

Oh, hey... actually, this could be *me*! Is this Tussock, by any chance? I have a build kind of like that (not New York, but skyline screens around a platform at I think about that height). And this morning I was just testing a physical elevator script that was giving me all kinds of fits, getting stuck for no apparent reason, and that may have been pretty laggy, but I'd have never noticed, buried in trying to debug the damned thing. (If not Tussock, then never mind.)

I also have not noticed negative effects from the use of MegaPrims.

I did once have a pretty bad experience with a freely and commonly available non-physical vehicle which I was testing, and had left out on the land when I logged off. I awoke the next morning to several angry IMs from the island owner that my single poorly-scripted object was bringing the sim's time dilation down to 0.5 constantly, and obviously affecting every other renter/visitor on the sim!


.

No, you're ok, it's not you.... LOL

Different SIM, though (as I'm at work) I can't remember the name of it now, but I know it's not Tussock

Thanks to all of you for the thoughts and advice so far.

Admittedly I have a number of (I'd guess) mosty simple scripts running on my plot.
A number or Prim and texture animation ones, a few rotations, couple of campfires, a butterfly poofer, a couple of water noise rocks, some firefly particle things that last a few seconds and a nice fountain.

From memory the statistics bar did say there were like 4500 odd scripts running, (not sure where they all are)

But........... and it's a "BIG BUT"..........

I just thought of something that I'll mention (I forgot about it earlier)

In the corner of the SIM underwater is a shipwreck with a diver in it (an Avatar) which I''m guessing is a BOT of some sort

I think he's quite new (avatar date 2009) and if you go into his profile, it says his job is to keep and eye on the SIMs performance (which when I first saw it, I though, that's good)

But I'm just wondering.....................

Do you think this means they have this Avatar/Bot running something that keeps checking the SIM and in some way ITSELF actually causing lag?

Or am I was off the mark here and any tool like that (running from an (Avatar/bot) 24 hours a day would not be the cause of this?

There are all sorts of nasty things a bot script *could* do to lag a sim pretty badly, but collecting the statistics (by bot or even by script) wouldn't be the first thing that came to mind, and especially not the kind of swings in dilation that you're reporting.

If you can get a handle on which part of processing (physics, image download, network, etc.) is swinging in phase with the overall frame time, that will give some clue where to look next. (These data are seen by expanding the Time line and the sub-lines that appear within, on the Statistics Bar. The wiki, http://wiki.secondlife.com/wiki/Statistics_Bar_Guide, gives some hints for interpreting the numbers.)

My hunch is that scripts will actually swing out-of-phase with frame time--that scripts will be getting throttled because too much other stuff is vying for the CPU, but that's just a hunch.

Also, you may be able to get a Linden expert out to investigate, by filing a support ticket. They can see data that (especially Mainland) owners just can't, to track down what specific stuff is lagging. (Or, they may reboot the sim and the problem mysteriously disappear never to return.)

Does it really do this every few seconds or is it closer to a minute? Could be a temp rezzer..

When you get back in-world, post the region name here..

No. Megaprims don't cause problems anymore. Only reason (= excuse) why Linden hasn't yet add support them for the viewer is that they are mass destruction weapon for griefers (like dropping super sized primitives to 16m2 parcel).

As said before, TimeDilation problem is likely caused by:
1. Scripts running in SIM
2. Physical objects in SIM (too many of them)
3. If SIM is not full SIM it is sharing processor with another SIM - thus another SIM can cause problems for SIM sharing processor with it.

Well.. I wouldn't say "megaprims can't lag the sim any more" because they can. They just don't do it nearly as much as they used to.

That said, if they're not set to physical in a place with lots of other physical or, maybe, if they not being used as a floor in a really high-traffic place, they're pretty harmless as far as the sim is concerned.

That bot in the corner sounds interesting. It could be owned by someone in the sim who uses it to gather data when s/he is doing/testing things that could cause the performance to deteriorate.

Well, sorta. Megaprims have been created from time-to-time, whenever a bug
crops up in the system to allow it. Then the megas are passed around by
people to use. The most common set of of megaprims are the ones created
long, long ago by Gene Replacement. These megaprims have a defect,
which is that they are not the shape and size they appear to be in-world.
Some of them are actually much bigger than they appear, because they
are Path Cut to look that way. They take up more space than it seems.
The only problem with that is that it can mess up the mini-map, and they
can invisibly protrude onto neighboring parcels. However, I understand
that the physics (collisions/non-Phantom) problems where they drove
the simulator crazy were solved a while back with the Havok 4 software.

Megaprims can also lie across sim boundaries, and with the old megas
you might not even realize that you're doing it. This used to cause some
kind of problem; don't know whether that's still true or not.

Megaprims do represent a large volume in which to detect collisions,
so they can cause that much lag. But not in the buggy sim-crashing
way as they often did before.

If you're just using them in your own space, megas are fine.
The Linden policy on them seems to vary depending on who you ask,
but I am pretty sure they are officially allowed on private islands, at least.
On the mainland, it is observed that the Lindens don't go around randomly
deleting people's megaprims as a matter of course, so they are at least
tolerated if there isn't some real problem happening.

Second Life could easily allow the creation of megaprims directly and
legitimately from the Viewer. Other grids have that. I'm not quite sure
why Linden Lab doesn't allow it.

Megaprims won't cause lag any more than normal ones, whether phantom, physical or normal. Supposedly they can increase sim crosstalk if placed on the border of a sim but from my experience any affect is minimal, if present at all.

As for why LL has yet to enable them, the only reference I can recall is that they want to get an option worked out so that you can return a prim that's overhanging your land, even if it's not centered on your land. This way even if someone rezzed a megaprim across half a sim or something, land owners can get rid of it without having to file ARs. Other than that issue, there isn't anything actually holding LL back on megaprims.

Btw, the original Gene Replacement megaprims should only be used if you need prims larger than 256x256. And the only people who really have any business rezzing such prims are private island/homestead/openspace owners since their sims are usually isolated and prims will not cross into other sims. Nobody else should be messing with them, especially on the mainland.

Really? Got a source for that statement? I think Andrew Linden has said differently..

As far as you TD goes, i highly doubt it is Mega prims causing that fluctuation.

Go to the very bottom of the Stats dialog and click the line named "time". Clicking this opens a few "sub times". This will help you see what is using too much time and effecting TD.

Most likely you are using too much physics time, or possibly script time. This is easily determined by looking at the "sub times".

If you determine it is a physics issue, you can use beacons to find to offending objects.
If you think it is scripts and you own or manage the region you can use top scripts to find the nasties.

(there was a H1 bug that caused mass collision issues with megas, i *thought* it was cleaned up in H4. Example, too many people standing on the same prim)


Please post your region name when you get a chance. There are lots of us troubleshooters here in the forums, just itching to fix your problem =))

Personal experience and numerous threads on the subject elsewhere in the forums (post-Havok1). During the Havok4 beta megaprims were apparently discussed into the ground and out the other side of the world. Browse through the blog posts and comments. If there was any significant negative effects LL could have and would have addressed them back then.

I've used megaprims extensively in building as I tend to work on larger scales. I've also seem some nice lag-free sims that had lots of megaprims and some horrid laggy ones with virtually none. Bad scripting/too many scripts is a much bigger factor than prims.

I've also experimented with them in physical form (the main problem area in the past) in sandboxes and when I had private land, and they behaved like any other prim. Dropping a few dozen 30x30x30 physical boxes (as an example) caused as much lag as the same number in 2x2x2 boxes. If the lag was any worse for the megaprims it was so small you won't notice it without an actual benchmark.

Lindens never say anything more officially, have never removed the megaprims though they could easily, I hear no validated reports of megaprims causing lag problems and have never encountered it myself (I started after H4 was grid-wide). I'm stepping out of this thread now because even I am sick and tired of the topic.

I know sim owners that still find that overhanging megas outside of the sim boundaries causes problems, from lag-like symptoms to other anomalies. This is post Havok4, and in unbounded sims where crosstalk is not an issue. There was a time not so long ago where if LL came to your sim for a support ticket and found a mega overhanging the boundary, they would just pick up and leave and tell you to call them when you had removed it since it was pointless for them to try and troubleshoot issues until that was resolved.

I hear normal prims cause lag too, try using 1000 10x10 floor panels sometime instead of a single megaprim.
I've seen peoples hair & boots lag a sim