User:Babbage Linden/Office Hours/2008 09 17

Transcript of Babbage Linden's office hours:

[8:01]	Nock Forager:	Hi Cale
[8:02]	Cale Flanagan:	hi noch and babbage
[8:02]	Nock Forager:	Hi Babbage
[8:02]	Babbage Linden:	hi everyone
[8:02]	Cale Flanagan:	(i meant nock)
[8:03]	Cale Flanagan:	oh some steam is coming:)
[8:03]	Babbage Linden:	everyone, i'd like to introduce scouse
[8:03]	Scouse Linden:	hello
[8:03]	Nock Forager:	Hi Scouse
[8:03]	Babbage Linden:	who has been working with me on mono for the last year
[8:03]	Cale Flanagan:	hello scouse, the smoker:)
[8:03]	Babbage Linden:	hi yuu
[8:03]	Scouse Linden:	*crunch*
[8:04]	Yuu Nakamichi:	hello :)
[8:05]	Babbage Linden:	let's wait a couple of minutes for people to turn up
[8:05]	Babbage Linden:	then i'll let you know where we are with mono
[8:05]	Cale Flanagan:	i wanst sure where to go, in ur picksis an office but thats elsewhere
[8:06]	Cale Flanagan:	oh i love that, i only see he tag:)
[8:06]	Babbage Linden:	ok, lets kick off
[8:06]	Fake Fitzgerald:	hi
[8:06]	Babbage Linden:	hi fake
[8:07]	Nock Forager:	low prim, eco av :)
[8:07]	Cale Flanagan:	and hide is only shoes:) wow
[8:07]	Babbage Linden:	later today we will be starting the roll of 1.24.6 to the main grid
[8:07]	Hidenori Glushenko:	lol
[8:07]	Babbage Linden:	which has been on the preview grid since monday
[8:07]	Babbage Linden:	the 2 main fixes for mono are the timer/rez/state_entry event problem
[8:08]	Babbage Linden:	and further hardening against the problems that were causing the C# error messages and crashes
[8:08]	Cale Flanagan:	like seeing something like .ctor?
[8:08]	Babbage Linden:	SVC-2908
[8:08]	Babbage Linden:	and
[8:09]	Babbage Linden:	SVC-2973
[8:09]	Babbage Linden:	(which are linked here: http://jira.secondlife.com/browse/SVC-1276)
[8:09]	Cale Flanagan:	maybe take a poke at svc-3066?:)
[8:09]	Babbage Linden:	with these 2 fixes, scripts should run as before on the original scripting engine
[8:10]	Cale Flanagan:	ur svc doesnt exist:)
[8:10]	Babbage Linden:	and there are no outstanding crash bugs that we know of
[8:10]	Babbage Linden:	so, now we'll turn to the mono only problems
[8:10]	Babbage Linden:	but likely we'll bundle them together
[8:10]	Babbage Linden:	rather than doing a 1.24.7 roll next week
[8:10]	Babbage Linden:	but we'll see
[8:11]	Babbage Linden:	we're currently looking at VWR-8997
[8:11]	Babbage Linden:	and SVC-3072
[8:11]	Babbage Linden:	as well as tuning the application domain unloading
[8:12]	Babbage Linden:	as we've seen domain unloading caused by some applications which start/stop and rez many different scripts
[8:12]	Babbage Linden:	now you should see domain unloading unless you stop 100 different scripts
[8:12]	Babbage Linden:	which should be very rare in normal operation
[8:13]	Babbage Linden:	we've also parameterised the domain unloader
[8:13]	Scouse Linden:	Stop 100 scripts, and there are no other copies running
[8:13]	Babbage Linden:	so we can tweak the parameters more easily
[8:13]	Babbage Linden:	so, we can tune the process over time
[8:13]	Babbage Linden:	to trade off frequency of domain unloads with size of simulator memory usage
[8:14]	Babbage Linden:	that's where we are at the moment
[8:14]	Babbage Linden:	if other crash bugs or problems with the original scripting engine come up we will jump on those
[8:14]	Babbage Linden:	otherwise we'll work through the mono issues to get mono scripts all working correctly
[8:15]	Cale Flanagan:	is mine 3066 prob also domain unloading related?
[8:15]	Scouse Linden:	No I'd guess not
[8:15]	Scouse Linden:	It looks like a new problem
[8:15]	Scouse Linden:	We will look at it as a high priority
[8:16]	Cale Flanagan:	thats good, bec my c experience told me, thaere can be something bad behind it
[8:16]	Babbage Linden:	have you tried this on 1.24.6 on the preview grid cale?
[8:16]	Babbage Linden:	it looks like something we may now catch
[8:16]	Cale Flanagan:	no, havent tried yet, can do after this
[8:16]	Babbage Linden:	thanks
[8:17]	Babbage Linden:	if you could add a comment letting us know whether this still occurs on 1.24.6 that would be great
[8:17]	Cale Flanagan:	i observed a bit more on this heap crashing scripts, what was the reason to stop them
[8:17]	Cale Flanagan:	i saw that they eat much simtime
[8:18]	Cale Flanagan:	i have them runing and crashed and having up to 6ms intop scripts
[8:19]	Babbage Linden:	that sounds strange
[8:19]	Babbage Linden:	each frame, each script should only get around 185us regardless of what it's doing
[8:19]	Babbage Linden:	to use 6ms of frame time for scripts you should need many of them
[8:20]	Cale Flanagan:	its only what top scripts is telling me, in statistic window i see no big impact on script time
[8:20]	Babbage Linden:	so, it may be a problem with top scripts
[8:21]	Babbage Linden:	has anyone else seen anything we should have a look at?
[8:21]	Nock Forager:	Not so. calm wind this week.
[8:22]	Babbage Linden:	that's good to know
[8:22]	Nock Forager:	ah I've got some tech text about Mono optimization.
[8:22]	Babbage Linden:	sounds like we're making progress :-)
[8:23]	Babbage Linden:	thanks nock
[8:23]	Babbage Linden:	where did you get the text?
[8:23]	Nock Forager:	From the auther, Jam Leili.
[8:24]	Nock Forager:	I talked with him and translated it in japanese already.
[8:24]	Babbage Linden:	thanks
[8:24]	Babbage Linden:	i'll have a read through it later and let you know if there are any misunderstandings
[8:25]	Cale Flanagan:	thanks nock
[8:25]	Nock Forager:	XLR do you need a copy?
[8:25]	Babbage Linden:	in general you should try to write easy to understand and maintain software
[8:25]	Babbage Linden:	and let us (and the mono developers) optimise the runtime
[8:26]	Babbage Linden:	if we change things in the future there is no guarantee that any of these tricks will continue to work
[8:26]	Nock Forager:	hmhm
[8:27]	Nock Forager:	The text explained not such as voodo magic, but maybe starndard in programings.
[8:27]	Scouse Linden:	The statements about eliminating variables are also probably not true
[8:27]	Nock Forager:	So I think it's ok.
[8:27]	Scouse Linden:	The compiler makes good use of variables
[8:27]	Babbage Linden:	i'll read through and let you know
[8:27]	Nock Forager:	thanks.
[8:27]	Cale Flanagan:	oh yes, u have a same-string detector somewhere?
[8:28]	Cale Flanagan:	i put over 7000times a 37 bytes string in a list (thast 500k)
[8:28]	Babbage Linden:	the way collection operations work
[8:28]	Babbage Linden:	is that they copy references around where they can
[8:29]	Babbage Linden:	so, when you add an int or vector to a list
[8:29]	Babbage Linden:	it gets boxed in to an object
[8:29]	Babbage Linden:	and then a reference to the object is stored in the list
[8:29]	Babbage Linden:	as you can't change the value while it's in a list
[8:29]	Babbage Linden:	if you copy the list around
[8:29]	Babbage Linden:	it just copies the references
[8:29]	Babbage Linden:	instead of copying the values
[8:30]	Babbage Linden:	so, if you put a string in a list
[8:30]	Babbage Linden:	then repeatedly copy the list or append it to another list
[8:30]	Fake Fitzgerald:	copy on write?
[8:30]	Babbage Linden:	the runtime copies a 4 byte reference to the string
[8:30]	Babbage Linden:	instead of the (many byte) string itself
[8:30]	Babbage Linden:	(it's kind of copy on write, yes)
[8:30]	Babbage Linden:	copy on unbox
[8:31]	Cale Flanagan:	i counted 8 bytes foreach entry:) regardless if a string or an int
[8:31]	Babbage Linden:	right
[8:31]	Babbage Linden:	there is an overhead from the arraylist
[8:31]	Babbage Linden:	and the object gets a vtable and sync data which adds 8 bytes
[8:32]	Cale Flanagan:	very interesting stuff, will this someday documented for hardcore scripters?:)
[8:32]	Babbage Linden:	yes, it's already in a couple of office hour notes :-)
[8:32]	Scouse Linden:	yes in the CIL Standard
[8:32]	Cale Flanagan:	oh great, thast a small book, i think:)))
[8:32]	Babbage Linden:	what we're doing here is different to how LSL handled lists and strings, so it's worth knowing about
[8:33]	Babbage Linden:	sorry, the original scripting engine ;-)
[8:33]	Cale Flanagan:	i als saw a difference in strings and keys
[8:33]	Cale Flanagan:	if i add a key as key or as string to a list
[8:33]	Babbage Linden:	in order to be able to differentiate between keys and strings
[8:33]	Babbage Linden:	a key is represented as a wrapped list
[8:34]	Babbage Linden:	so a key object has a reference to the string it wraps
[8:34]	Babbage Linden:	whereas a string is just a CLI string
[8:34]	Babbage Linden:	it's unfortunate that we had to differentiate them
[8:34]	Babbage Linden:	but we did
[8:34]	Babbage Linden:	it's also unfortunate that you can store any string in a key
[8:35]	Babbage Linden:	which could otherwise be represented more concisely as a UUID
[8:35]	Cale Flanagan:	then u could have saved them as real keys:) i found a way to save some space with utf coding, ist a bit hell but 22bytes for a key is good
[8:36]	Babbage Linden:	hopefully one day we'll be able to provide CLI byte arrays
[8:36]	Babbage Linden:	and access to the GUID class
[8:36]	Babbage Linden:	and provide implicit conversion operators that will create a LindenLab.SecondLife.Key from a CLI GUID
[8:36]	Babbage Linden:	so you can store keys in a few bytes
[8:37]	Cale Flanagan:	sounds good
[8:37]	Babbage Linden:	but we can maintain compatibility with the existing API
[8:37]	Babbage Linden:	which allows you to pass a Key with the value "thisisnotakey"
[8:37]	Cale Flanagan:	y, u can simply flag them...
[8:38]	Yuu Nakamichi:	sorry if this has been brought up earlier but I was wondering if there's still help needed on svc-2908
[8:39]	Yuu Nakamichi:	(the c# error messages)
[8:39]	Babbage Linden:	there still seem to be some problems that cause C# error messages
[8:39]	Babbage Linden:	(that JIRA task became a dumping ground for many different issues)
[8:40]	Yuu Nakamichi nods
[8:40]	Babbage Linden:	if you look at baron nowhere's last comment he can still get error messages about arrayindexoutofbounds
[8:40]	Babbage Linden:	so if you see anything around that, please let us know in the jura
[8:40]	Yuu Nakamichi:	ok
[8:40]	Babbage Linden:	i think it's caused by the scripts count of pending events
[8:41]	Babbage Linden:	and queue of pending events getting out of sync
[8:41]	Babbage Linden:	we could defensively code around it
[8:41]	Babbage Linden:	by checking the event queue before taking the next event
[8:41]	Babbage Linden:	but that would mask the problem
[8:41]	Babbage Linden:	it would be better to be able to identify how the counts get out of sync
[8:42]	Yuu Nakamichi:	I'm happy to lend a hand with testing on the preview grid
[8:43]	Yuu Nakamichi:	I see vektor has been testing it there
[8:43]	Babbage Linden:	yes
[8:43]	Babbage Linden:	probably our approach going forward will be to work on the most easily reproducable issues
[8:43]	Babbage Linden:	and wait for information on the others
[8:43]	Babbage Linden:	gathered from running the latest code on the grid
[8:44]	Babbage Linden:	for example, i think the c# error message issue should become clearer once 1.24.6 is deployed
[8:44]	Babbage Linden:	to the main grid
[8:44]	Babbage Linden:	which will clear away lots of reports of the errors we've fixed
[8:44]	Babbage Linden:	which may make the remaining issues clearer to understand
[8:44]	Yuu Nakamichi:	got it
[8:45]	Babbage Linden:	so, i'm looking forward to people playing with 1.24.6 on the main grid
[8:45]	Babbage Linden:	and collecting information for us to look at next week
[8:45]	Babbage Linden:	some of the problems we've fixed were very intermittent
[8:45]	Babbage Linden:	and caused by invalid memory
[8:46]	Babbage Linden:	making them difficult to reason about
[8:46]	Babbage Linden:	and meaning that many errors had the same cause but different symptoms
[8:46]	Babbage Linden:	hopefully we've fixed all the invalid memory issues and so should be left with more logical errors
[8:46]	Babbage Linden:	or even better, no errors at all :-)
[8:47]	Cale Flanagan:	if there are no bugs, there must be something broken:)
[8:48]	Babbage Linden:	any more questions?
[8:48]	Babbage Linden:	comments?
[8:48]	Babbage Linden:	suggestions?
[8:49]	Cale Flanagan:	if i start with my wishlist...:)
[8:49]	Yuu Nakamichi:	the mono OH are now here, once a week?
[8:49]	Babbage Linden:	periapse also holds an office hour on fridays
[8:49]	Babbage Linden:	at 3PM pacific time i think
[8:50]	Babbage Linden:	the details are in the wiki
[8:50]	Yuu Nakamichi:	ok thx :)
[8:50]	Babbage Linden:	but yes, i hold office hours here at 8AM on wednesdays
[8:50]	Babbage Linden:	at the moment they are mostly about the mono deploy
[8:50]	Babbage Linden:	but i hope to talk about scripting and technology more widely as we get the mono deploy all smoothed out
[8:51]	Yuu Nakamichi:	great :)
[8:52]	Nock Forager:	Nice. I hope you come to our convention and talk about Mono some :) http://lsl-con.org/2008/lsl-convention-2008-en.php
[8:53]	Babbage Linden:	i'll have to see what i can do
[8:53]	Nock Forager:	(Sorry, it's bit Japanese language depended).
[8:53]	Babbage Linden:	thanks for the invitation :-)
[8:53]	Babbage Linden:	are you also holding it in world?
[8:53]	Babbage Linden:	i imagine i could definitely come to that
[8:54]	Yuu Nakamichi:	wow thanks nock
[8:54]	Nock Forager:	Yes it's in-world event. at "New Script" region.
[8:54]	Babbage Linden:	excellent
[8:54]	Yuu Nakamichi:	what's the date?
[8:55]	Nock Forager:	date... ops I forgot to write it on the page. I should add.
[8:55]	Nock Forager:	it's 2008/10/18 to 2008/11/02.
[8:55]	Yuu Nakamichi:	cool thx :)
[8:55]	Yuu Nakamichi:	two weeks? :)
[8:56]	Nock Forager:	Yes, weekend for some session talk.
[8:56]	Yuu Nakamichi:	excellent
[8:57]	Yuu Nakamichi:	is this the first resident-driven convention that focuses on LSL?
[8:57]	Babbage Linden:	thanks nock
[8:57]	Nock Forager:	Not so. we did it in 2007 too.
[8:57]	Babbage Linden:	i'll let you know if i can make it
[8:57]	Yuu Nakamichi:	I see.
[8:58]	Nock Forager:	Thanks Babbage. We'll make your sheet reserved. :)
[8:58]	Babbage Linden:	ok, any last questions
[8:58]	Babbage Linden:	?
[8:59]	Cale Flanagan:	i only have to say thanks for all answers
[8:59]	Babbage Linden:	np
[8:59]	Babbage Linden:	thanks for coming everyone
[8:59]	Babbage Linden:	i'll see you all next week
[8:59]	Fake Fitzgerald:	thanks Babbage
[8:59]	Yuu Nakamichi:	thanks babbage
[8:59]	Nock Forager:	Thanks for meeting. see you in next week.
[8:59]	Fake Fitzgerald:	see you next
[8:59]	Babbage Linden:	bye!
[8:59]	Cale Flanagan:	(and the teddy:))
[9:00]	Cale Flanagan:	bye