Ask New 2.4 Maintainer Marcelo Tosatti Anything

Linus keeps hinting (declaring, even) that he's nearly ready to work full-time on the 2.5 development branch of his kernel, and hand the 2.4 kernel off to Marcelo Tosatti. Marcelo's graciously agreeed to answer questions (you might want to read some of his mailing list contributions first), so here's your chance to ask him what he'll do in the famous footsteps of Linus and Alan Cox, and how he got there. Please only put one question per post; we'll pass along the top-rated comments to Marcelo for his answers, and hear back from him shortly.

My Question

[ekrout]

Will Alan Cox's choice to not unveil security changes in the kernel changelog potentially affect other developers?

background

[-tji]

For those of us not part of the kernel community, can you give us an overview of your background and past work done in the Linux world?

2.4 and 2.5

[Anonymous Coward]

How much do you expect to be backported from 2.5? Obviously there's a lot of stuff people are interested in putting in the kernel, but should probably refine in a development kernel first (e.g. XFS, JFS, preemption, lowlatency, etc.)

Money

[bnatale]

Does someone pay you for working on linux, do you have another job where you can earn some money to buy food or do you have to beg on the mainstreet in your spare time?

Hit by a bus

[moonboy]

I'd hate to stray from the status quo where standard interview questions are concerned, so in keeping with it, I ask:

What's it like knowing that, if (God forbid) Linus and Alan were hit by a bus, you might be "The Man"?

Hey, someone had to ask.

Hardware to support in 2.4?

[Lumpish Scholar]

What hardware do you think will need additional support in the 2.4 branch? Big (>150G) hard disks? KT266A and/or nForce chipset motherboards? USB 2.0?

Expectations

[MikeBabcock]

In the time you've been aware of or been using Linux, how have your expectations for what it ought to be or eventually become changed? I know in the time I've used it I'd never expected it, for example, to become a desktop OS but rather a good server or embedded product. What did you expect when you first started with Linux, and what do you expect now?

Age a question

[debrain]

If what I've read is correct, you are the youngest maintainer for this kernel. Do you have any feelings on a social level, regarding much of the peer review and critism will come from people who are older? (and very possibly set in their ways, and potentially intimidating)

Preemptile

[bnatale]

Ok, here comes the question that everyone wants to have answered: When will the patches to make linux fully preemptile be included in the official kernel?

security patches in the Changelogs?

[LMCBoy]

Will you be following Alan Cox's lead by withholding security patch information from the kernel Changelogs?

Threads

[Exmet Paff Daxx]

What are your thoughts about threads? Specifically, do you support Linus's "Context of Execution" generality with clone() or are you going to focus more on plain POSIX pthreads compliance?

Any chance of Alan Cox's multi-threaded post-mortem debugging patch which dumps multiple core files for each lightweight process (LWP) making it into the kernel? How about support for post mortem debugging of multithreaded core files in general (right now there is zero support).

Any rants about threading as a general topic would work.

Time for renumbering?

[cperciva]

While linux has a tradition of giving stable kernels even subversions and unstable kernels odd subversions, the history of the 2.4 kernel has been far from stable so far.

Wouldn't it make more sense to take 2.4.14 (or 2.4.15 whenever it comes out) and call that 2.5.0, while moving the unstable kernels over to 2.6? While it would break the even/odd numbering paradigm, that seems a better option than having a subversion which starts out unstable and partway through morphs into a stable form.

Stability vs Features

[azaroth42]

How do you intend to decide which new patches should be added to 2.4, the stable tree, and which are not to be included as being more appropriate to just 2.5, the unstable development tree?
For example, do new or updated device drivers rank more highly than VM updates?

-- Azaroth

How do you plan to handle the big companies?

[hansendc]

As all of us know, many large companies are putting large amounts of resources toward Linux. 2.4 will continue to be important to these companies because it is the version currently being shipped with the distributions, and will continue to be shipped for at least a year or two.

How are you going to deal with the submissions from people like IBM and SGI who are going to want to make significant changes to 2.4?

Do you use a distribution?

[martinde]

If you use a distribution, which one and why? How about a GUI environment? VI or emacs?

Alan Cox and politics

[melquiades]

Alan Cox's stand on the changelog is clearly not only a matter of personal protection, but a political statement. He has chosen an issue that is tremendously important to Linux, free software, and software developers everywhere, and certainly it's right for him to be pursuing it.

But is the Linux kernel the right forum for politics? Do you feel that it's a bad idea to involve the kernel in politics -- a slippery slope in which the software itself becomes a political pawn? Or would you say that the kernel -- and all software -- has already become a political pawn, and Cox's actions are entirely justified given that free software's existence is under increasing threat?

Human interest

[ChrisJones]

What scares you the most about taking on this fairly hefty responsibility?

The Deal with Marcelo, Alan and Linus?

[Zeio]

This is a mixed question/comment.

What is going on here?

It seems that Alan has stopped doing his -AC series...

Linus is finishing up 2.4.X after making some deep changes to the VM (Adrea's new VM), and thankfully adding EXT3, but form what I have been reading, 2.4.15 is the end of the stable kernel series (with no XFS or JFS support which is upsetting).

Andrea has a plethora of experimental/tweaked patches in ftp.kernel.org/pub/linux/kernel/people/andrea. What is interesting/worrisome to me is that Marcelo's directory there is empty.

Marcelo must be a great guy, I've seen a lot of banter on newsgroups with him, and a few chages in the stable changelog here and there, but to me it looks like a lot of talk. Alan used to release (past tense, it seems it has stopped) AC patches on a near daily basis, to me, Marcelo is vapor.

Is the maintainer's jobs simple to make small changes to the kernel when errata is found? Or is it, as Alan has done, to integrate and merge a LOT of stuff to produce a useful and robust hybrid kernel and then suggest that maybe the unbroken things should be merged in.

I wish Marcelo luck in this endeavor, but also wish to see loads of "maintainence," Linux really, really needs feverish active development, and there a lot of people, Like Alan and Linus, who put out quite a bit. I am hoping Marcelo will set a new precedent for uber-feverish maintenance - maybe even see XFS and JFS and other things that the distributions have to waste huge amounts of time tinkering and adding various enterprise-ish things to make the Linux kernel stand up for, as they put it, prime time.

Money

[bribecka]

I'm assuming that maintaining the kernel is a volunteer, non-paying position. And since it takes money to live in this world, how do you find time to actually earn a living while keeping up with the kernel?

Kernel releases

[Anonymous Coward]

How do you feel about the recent increase in kernel releases every few odd weeks? Looking at your mailing list contributions, I get the impression that recent kernels seem to have more bugs/features than previous kernels (then again, I am new to Linux). Specifically, do you feel Linus and Co. have been hasty with their work?

CML2, cvs, kdb, crypto and more

[iamsure]

If during the course of your maintainership CML2 proves very successful (as I beleive it already has) would you consider using it instead of CML1?

Also, would you consider moving crypto into the main tree in the near future? Debian has, Redhat will "soon"..

Would you consider using bitkeeper, cvs, or even complete changelogs with proper attribution of WHICH merges took place?

And finally, would you consider FINALLY bringing kdb into the main kernel? Linus doesnt want it, but he doesnt want it because he doesnt see the value. He didnt say he banned it..

Patches

[return 42]

Linus likes very small patches, everything broken down into little chunks of functionality. Alan is ok with bigger patches. What do you like and dislike in the patches people send you?

Why you?

[CmdrPinkTaco]

This is not intended as a flame or a troll, more of an interview style question. I figure since we are the people who are putting our trust in this person to handle *our* kernel, that this should also be our chance to learn about the person responsible.

What makes you think that you can handle maintaining the Linux Kernel? What qualifications do you have and why should we (the people) trust you with the Linux kernel.

I realize that this is actually two questions, but they more or less go together in one answer.

Interaction with distros

[DaoudaW]

A number of distros are already using 2.4.x. I am curious how much of the maintenance of the 2.4 kernel will be simply incorporating changes already made by the different distros, how much will be making changes in response to distro requests, and how much of the process is independent from the distros?

A pretty generic question

[archen]

How do you view Linux in the scheme of things? Mainly where do you think the niche of Linux is now, and where will it be years from now. How do you view the direction Linux tends to be taking compared to other OS's (Windows XP, FreeBSD, etc) - ["direction" is up to what ever you personally interpret it to be BTW]

Any plans to improve documenting the kernel?

[Carnage4Life]

Currently the Linux kernel is filled with functions that are either poorly documented or completely undocumented. One of the purported benefits of Free Software is that many developers can jump in and help yet when you have functions like __free_pages_ok [linux.no] in page_alloc.c that are important, complex yet the only comment is

Buddy system. Hairy. You really aren't expected to understand this.

doesn't this somehow defeat the point of the source being available in the first place? Basically the question I have to ask is this, "I have flirted with the thought of sending comment only patches to the kernel to further help people understand certain subtleties (e.g. why the pprev and next pointers in user_struct are not what they seem) in the source code especially CS students who are learning about the kernel in operating systems classes. If someone were to start such a program would such patches be accepted into the kernel?

Are you ready.......

[the_2nd_coming]

Are you Ready and psychologically prepared to become one of the Linux head Honchos? I mean in about a year or so, people will be throwing your name around places like /. and Linux today as freely as they do now with Linus and Alan.....Do you think it will be difficult for you to handle the sudden fame?

code control

[brer_rabbit]

Have you thought about putting your changes under some sort of version control software? If you started putting the kernel/patches under CVS, maybe the rest of the kernel crowd would follow.

National biases.

[saintlupus]

In your experience, is the kernel development genuinely international and multilingual, or are there tensions between developers from different regions or who speak different native languages?

--saint

A question

[jd]

Will you replace the VM system, the first chane you get? :)

No, the -real- question is whether you will be treating 2.4.x as a "maintained but dead" branch, or whether you'll be actively beating the code senseless with a (plank *) twoByFour?

(Quick followup: If you -are- going to actively develop 2.4.x, will you be restricting that to merging in 2.5.x code, or will you be seeking out new patches, boldly coding where no kernel has gone before?)

Conectiva & Kernel & Security

[GdoL]

As a brazilian citizen (and Conectiva employee), will you be free to publish anything on the changelogs?

Kernel growth -- is it a problem?

[connorbd]

While I am a passionate Linux supporter, I have also come to the conclusion that kernel bloat is likely to be a major issue fairly soon. It appears to have been the case for some time that =486 systems Need Not Apply, and Red Hat in particular has become a rather memory-hungry distro (it won't even install on my 16MB Pentium system, though I doubt this is really a kernel issue). The end result is that Linux seems slowly to be growing out of the lower-end used-server-in-a-closet market that helped it get so big in the first place.

My question: I presume kernel bloat, both in terms of code size and resource demands, can impact heavily on maintainability. Do you see this as a significant issue for the future, how much of a problem is it, and is it something that can be easily addressed without tearing apart the code base and reorganizing it from the ground up?

/Brian

diary

[Lennie]

Do you have a diary, like Alan Cox we can read ?

Because we all like to know, if you'll actually be doing what your gonna promise now :)

How often

[Cro Magnon]

Lately, Linus has been releasing a new 2.4 version every month (sometimes more). Will you continue at that pace, or slow it down?

Age

[FreakOfTheWeek]

How will you respond to criticism from the corporate world (most of whom don't understand what linux is, let alone a kernel), that "linux" is being maintained by an 18 year old?
Do you think this will reflect badly on the image of linux? (as seen from IT decision makers)

Google/VM/Corporate influences

[slick_rick]

While browsing through the kernel mailing list a while back... I noticed a post [theaimsgroup.com] that went unanswered about some specific problems Google was having with 2.4 kernels and the new/old VM.
It seems obvious from this post that Google can't use 2.4 until this gets worked out, and Google is one of Linux's big success stories...

How does that weigh in on the todo scale versus my problem with the Visor driver? What if it was Connectiva that had the problem? (Or Redhat?)

(and a quick second question: How can any human read teh 7000 posts a month to the mailing list and still get any coding done?)

Re:Do you use a distribution?

[bfree]

To rewrite the above question the way I'd like it asked:

What operating systems and platforms do you personally use and which ones do you also use (and why)?

Do you run a common environment on all your machines (in as far as possible) or do you run different things in different places and which environments do you prefer for what?

What development tools do you use (especially for the kernel), would you do anything differebtly for the kernel (like make it compile with other compilers) if you could (or will you) and would you like to (or will you) place the Linux stable kernel into CVS or another version control system?

Do you feel any personal preferences for anything might actually be in anyway reflected in your work as the stable kernel maintainer?

Do you have a good lawyer? Are you planing on travelling to the U.S.A. (for all I know you live there, excuse my ignorance:-)? Have you experience dealing with politicians, business leaders and large groups and do you see this as a part of your job description?

When you stop maintaing the stable kernel, what would you like people to be saying about your reign?

Linux or BSD :-)

Boot Messsages

[x00]

Linus has stated that he'd like to get rid of a lot of the "non-informational" messages on boot and with this I have to agree with him.

Do you plan on furthering this cause, and helping make our boot times a simpler, less complicated read?

Features vs Stability

[spudgun]

Do you intend to bend to popular demand for features at the price of stability or is stability king in the stable kernel ?

Conectiva issues

[Stonehead]

Is Conectiva going to let you spend all your time to the 2.4 kernel?
I read that you live in the same house as Rik van Riel, who wrote the first Linux 2.4 VM and who also works for Conectiva. Rik wrote in his not-that-very-often updated diary that he travelled a lot in Brazil, to help customers anywhere. That takes a lot of time. Is your job going to be different once Alan Cox passes the maintainership?

orphaned branch

[Anonymous Coward]

Marcello,

Any chance that sun-32 will be maintained again?
Since 2.3.5 all we hear is: be patient....
All sun support is currently for 64-bit users
Kernel code does not even compile anymore!

Re:Any plans to improve documenting the kernel?

[cymen]

How can something be impossible to document? If the person understands the problem well enough to write the code, they should be able to express the same thoughts and intentions in English comments.

When you write code you write for a specific standard (or compiler or interpreter) but when you write English you write for unknown. Descriptions could at some point get more lengthy than code. Would that be bad? I don't know. I'd rather have the information than not, personally. But I can see why bibles of information are kept out of the kernel.

stuff&life....

[rarruda]

Hi Marcelo,

I have grown to respect quite a bit you as well as some of the other folks who work in kernel development at conectiva in Brazil (Rik, Arnaldo..).

I have been wanting to try to read more and more about the linux kernel, and maybe(?) try to get involved, so i must ask how did you start out? Any pointers that i should follow to get to understand more deeply the kernel? I mean you are not in heavy kernel hacking and you are a few years younger than me... (My guess is that it wasnt in college, since by now you should be doing the infamous college entrance exams... aka vestibular =P)

Also it seems that you value your privacy, since there isnt much public information about you out there... Would you elaborate a little on how you got where you are? =)

Just one more thing... I feel i must say that all Brazilians and young people in general are very proud and happy to see where you are now! Thanks a lot and keep up the good work!

Re:Money

[sg_oneill]

Noe *that* raises an interesting point. Since you are working at Concectiva (perhaps with Rik?) , what is your take on the Rik VM vs Andrea VM debate (largely resolved presumably) and is it even relevant anymore

question for Marcello

[Apostata]

Not that I wish to put you in an uncomfortable situation, but would it be possible to get your reaction to Eric S. Raymond's comment about the state of kernel development:

"I've been examining the existing kernel configuration system, and I have about concluded that the best favor we could do everybody involved with it is to take it out behind the barn and shoot it through the head."

For someone as persuasive and influential as Raymond to make such a statement, it begs for a response, if not a rebuttal.