Message-ID: <555270FF.20508@ontolab.com>
Date:	Tue, 12 May 2015 23:30:39 +0200
From:	Christian Stroetmann <stroetmann@...olab.com>
To:	Daniel Phillips <daniel@...nq.net>
CC:	David Lang <david@...g.hm>, Theodore Ts'o <tytso@....edu>,
	Howard Chu <hyc@...as.com>, Dave Chinner <david@...morbit.com>,
	linux-kernel@...r.kernel.org,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Pavel Machek <pavel@....cz>, tux3@...3.org,
	linux-fsdevel@...r.kernel.org,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: xfs: does mkfs.xfs require fancy switches to get decent performance?
 (was Tux3 Report: How fast can we fsync?)

On 12.05.2015 22:54, Daniel Phillips wrote:
> On 05/12/2015 11:39 AM, David Lang wrote:
>> On Mon, 11 May 2015, Daniel Phillips wrote:
>>>> ...it's the mm and core kernel developers that need to
>>>> review and accept that code *before* we can consider merging tux3.
>>> Please do not say "we" when you know that I am just as much a "we"
>>> as you are. Merging Tux3 is not your decision. The people whose
>>> decision it actually is are perfectly capable of recognizing your
>>> agenda for what it is.
>>>
>>>    http://www.phoronix.com/scan.php?page=news_item&px=MTA0NzM
>>>    "XFS Developer Takes Shots At Btrfs, EXT4"
>> umm, Phoronix has no input on what gets merged into the kernel. they also hae a reputation for
>> trying to turn anything into click-bait by making it sound like a fight when it isn't.
> Perhaps you misunderstood. Linus decides what gets merged. Andrew
> decides. Greg decides. Dave Chinner does not decide, he just does
> his level best to create the impression that our project is unfit
> to merge. Any chance there might be an agenda?
>
> Phoronix published a headline that identifies Dave Chinner as
> someone who takes shots at other projects. Seems pretty much on
> the money to me, and it ought to be obvious why he does it.

Maybe Dave has convincing arguments, that have been misinterpreted by 
that website, which is an interesting but also highliy manipulative 
publication.

>>> The real question is, has the Linux development process become
>>> so political and toxic that worthwhile projects fail to benefit
>>> from supposed grassroots community support. You are the poster
>>> child for that.
>> The linux development process is making code available, responding to concerns from the experts in
>> the community, and letting the code talk for itself.
> Nice idea, but it isn't working. Did you let the code talk to you?
> Right, you let the code talk to Dave Chinner, then you listen to
> what Dave Chinner has to say about it. Any chance that there might
> be some creative licence acting somewhere in that chain?

We are missing the complete useable thing.

>> There have been many people pushing code for inclusion that has not gotten into the kernel, or has
>> not been used by any distros after it's made it into the kernel, in spite of benchmarks being posted
>> that seem to show how wonderful the new code is. ReiserFS was one of the first, and part of what
>> tarnished it's reputation with many people was how much they were pushing the benchmarks that were
>> shown to be faulty (the one I remember most vividly was that the entire benchmark completed in<30
>> seconds, and they had the FS tuned to not start flushing data to disk for 30 seconds, so the entire
>> 'benchmark' ran out of ram without ever touching the disk)
> You know what to do about checking for faulty benchmarks.
>
>> So when Ted and Dave point out problems with the benchmark (the difference in behavior between a
>> single spinning disk, different partitions on the same disk, SSDs, and ramdisks), you would be
>> better off acknowledging them and if you can't adjust and re-run the benchmarks, don't start
>> attacking them as a result.
> Ted and Dave failed to point out any actual problem with any
> benchmark. They invented issues with benchmarks and promoted those
> as FUD.

In general, benchmarks are a critical issue. In this relation, let me 
quote Churchill in a derivated way:
Do not trust a benchmark that you have not forged yourself.

>> As Dave says above, it's not the other filesystem people you have to convince, it's the core VFS and
>> Memory Mangement folks you have to convince. You may need a little benchmarking to show that there
>> is a real advantage to be gained, but the real discussion is going to be on the impact that page
>> forking is going to have on everything else (both in complexity and in performance impact to other
>> things)
> Yet he clearly wrote "we" as if he believes he is part of it.
>
> Now that ENOSPC is done to a standard way beyond what Btrfs had
> when it was merged, the next item on the agenda is writeback. That
> involves us and VFS people as you say, and not Dave Chinner, who
> only intends to obstruct the process as much as he possibly can. He
> should get back to work on his own project. Nobody will miss his
> posts if he doesn't make them. They contribute nothing of value,
> create a lot of bad blood, and just serve to further besmirch the
> famously tarnished reputation of LKML.

At least, I would miss his contributions, specifically his technical 
explanations but also his opinions.

>>> You know that Tux3 is already fast. Not just that of course. It
>>> has a higher standard of data integrity than your metadata-only
>>> journalling filesystem and a small enough code base that it can
>>> be reasonably expected to reach the quality expected of an
>>> enterprise class filesystem, quite possibly before XFS gets
>>> there.
>> We wouldn't expect anyone developing a new filesystem to believe any differently.
> It is not a matter of belief, it is a matter of testable fact. For
> example, you can count the lines. You can run the same benchmarks.
>
> Proving the data consistency claims would be a little harder, you
> need tools for that, and some of those aren't built yet. Or, if you
> have technical ability, you can read the code and the copious design
> material that has been posted and convince yourself that, yes, there
> is something cool here, why didn't anybody do it that way before?
> But of course that starts to sound like work. Debating nontechnical
> issues and playing politics seems so much more like fun.
>
>> If they didn't
>> believe this, why would they be working on the filesystem instead of just using an existing filesystem.
> Right, and it is my job to convince you that what I believe for
> perfectly valid, demonstrable technical reasons, is really true. I do
> not see why you feel it is your job to convince me that the obviously
> broken Linux community process is not in fact broken, and that a
> certain person who obviously has an agenda, is not actually obstructing.
>
>> The ugly reality is that everyone's early versions of their new filesystem looks really good. The
>> problem is when they extend it to cover the corner cases and when it gets stressed by real-world (as
>> opposed to benchmark) workloads. This isn't saying that you are wrong in your belief, just that you
>> may not be right, and nobody will know until you are to a usable state and other people can start
>> beating on it.
> With ENOSPC we are at that state. Tux3 would get more testing and advance
> faster if it was merged. Things like ifdefs, grandiose new schemes for
> writeback infrastructure, dumb little hooks in the mkwrite path, those
> are all just manufactured red herrings. Somebody wanted those to be
> issues, so now they are issues. Fake ones.
>
> Nobody is trying to trick you. Just stating a fact. You ought to be able
> to figure out by now that Tux3 is worth merging.
>
> You might possibly have an argument that merging a filesystem that
> crashes as soon as it fills the disk is just sheer stupidity than can
> only lead to embarrassment in the long run, but then you would need to
> explain why Btrfs was merged. As I recall, it went something like, Chris
> had it on a laptop, so it must be a filesystem, and wow look at that
> feature list. Then it got merged in a completely unusable state and got
> worked on. If it had not been merged, Btrfs would most likely be dead
> right now. After all, who cares about an out of tree filesystem?

I would like to say two points to this statement:
Firstly, Btrfs was supported by Oracle, which is definitely a totally 
different size than a small group of developers.
Secondly, you are right with your complains. Said this, we do not want 
to make the same mistake with Tux3 or any other file system once again.

>
> By the way, I gave my Tux3 presentation at SCALE 7x in Los Angeles in
> 2009, with Tux3 running as my root filesystem. By the standard applied
> to Btrfs, Tux3 should have been merged then, right? After all, our
> nospace handling worked just as well as theirs at that time.

As far as I can remember from the posts on the mailing list, Tux3 has 
changed so significantly in the last 6 years with features that I always 
reference, that it cannot be the same compared with what has been 
presented in 2009 anymore.

>
> Regards,
>
> Daniel

Thanks
Best regards
Have fun
C.S.
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