Jorge Timón 於 2015-08-30 14:56 寫到:
On Sun, Aug 30, 2015 at 7:13 PM, <jl2...@xbt.hk> wrote:
This is based on the assumption that miners would always like to use
up the
last byte of the available block size. However, this is just not true:
1. The 6 year blockchain history has shown that most miners have a
soft cap
with their block size.
2. Chinese miners, controlling 60% of the network, rejected Gavin's
initial
20MB proposal and asked for 8MB:
http://cointelegraph.com/news/114577/chinese-mining-pools-propose-alternative-8-mb-block-size
[...]
No, I'm not making such assumption. I'm focusing on what they CAN do,
while suspending judgement on their good will and not trying to
predict their future behavior from historic behaviour.
With 60% of the hashrate, you can easily get 100% by orphaning
everybody else's blocks. More importantly, being under the same
jurisdiction they can be forced to behave in certain way (for example,
censor transactions) by law.
I'm very worried about the current situation no matter how benevolent
current miners are. Thus weakening the only limit to mining
centralization that we have at the consensus rule level seems
extremely risky at this point.
The reason for 60% of block were generated in China is same as the
reason for 60% of your clothes were made in China. The electricity there
is the cheapest on the planet. Many dams were built in the past 10 years
and now they have huge amount of surplus electricity due to economic
downturn.
Not sure if you are aware of this thread:
https://bitcointalk.org/index.php?topic=1072474.0 . Could you imagine
this in any developed country? As long as mining is largely dependent on
energy, there is no hope to break the balance/imbalance.
Bandwidth is probably only a few percent of miners' cost. There is no
evidence that the current level of centralization is a result of block
size. Instead, clear evidence has shown that centralization is a result
of pool mining*, invention of ASIC, and disparity of energy cost. (*
People started pool mining in 2010 because they wanted lower variance,
not because of the inability to run a full node)
For many reasons miners may want to have a smaller block size, which
we
don't need to list them here. Although they can limit it by a softfork
or
even 51% attack, it is a very violent process. Why don't we just allow
them
to vote for a lower limit?
So I think the right way is to choose a mining-centralization-safe
limit,
and let it free float within a range based on miner's vote. If we are
lucky
enough to have some responsible miners, they will keep it as low as
possible, until the legitimate tx volume catches up. Even in the worst
case,
the block size is still mining-centralization-safe. The upper limit
may
increase linearly, if not exponentially, until we find a better
long-term
solution. (sort of a combination of BIP100 and 101, with different
parameters)
My point is, a "soft cap" determined by miners clearly doesn't protect
us from mining centralization: the "hard cap" does.
Knowing that, and given that miners can currently set their own policy
block size maximum, what does this "voting on a lower limit" achieve?
What are the gains? Why are we "lucky" if they keep the lower one as
low as possible?
Even if we could quantify the level of centralization, it is a continuum
and we must compromise between utility and centralization. Unless
BIP101/103 is adopted, adjusting the hard cap always require a hardfork.
For obvious technical and political reasons we can't have hardfork too
frequently. Therefore, we need to leave some leeway: the hard cap may be
a bit too high for today, but we are sure that technology will catch up
in the near future.
Assuming we have plenty amount of "benevolent" miners, they will keep
the block size low unless there is a real demand for larger block space.
This is different from setting an individual soft limit, as that will
lead to block size scarcity and therefore higher tx fee, which may be
good for all miners. And as we say "miners can always decrease the block
size with softfork or 51% attack", BIP100 materializes this possibility
in a much smoother way.
I say "lucky" because I wholeheartedly believe it is good to keep the
block as small as we really need. We can't do this by an equation so I
would prefer to leave the power to miners (and they always have this
power, anyway).
For the matter of "urgency", I agree with you that there is no actual
urgency AT THIS MOMENT. However, if a hardfork may take 5 years to
deploy
(as you suggested), we really have the urgency to make a decision now.
Thank you for admitting it is not urgent!
I suggested 5 years for the concrete hardfork in bip99 because it's
clearly non-urgent and I wanted to be very conservative. I'm happy to
reduce that to say, 1 year (specially given that the change is very
simple to implement).
For a simple block size change (like, say bip102) 1 year (maybe 6
months + miner's confirmation) is probably more than enough as well.
And we can always deploy an urgency hardfork if it is necessary.
Actually, the main point is not urgency but uncertainty. We have
debated for
5 years. Why won't we have 5 more years of debate, plus 5 years of
deployment delay? Are we sticking to 1MB for 10 years? In that case
Bitcoin
Core must be abandoned by the economic majority and a Schism fork must
occur.
Fortunately we haven't been discussing this for 5 years, I don't know
where you get that from.
Jeff and Satoshi discussed this in 2010, although the flame throwing
debate did not start until 2013.
A schism fork it's certainly always a possibility but I would only
consider it after an urgency hardfork (once the issue becomes urgent)
fails due to not being uncontroversial.
Would you agree with me on that?
What would be your criterion for considering an increase in block size
urgent?
The problem is the definition of "urgency" itself is controversial. And
I believe an urgent hardfork should only be done as a bug fix, not
implementation of a new feature. Block size increase should be a planned
feature, as we don't want the tx fee raised to 10USD, before suddenly
dropping to 0.01USD with the hardfork.
I don't think it's urgent today because my free tx always get mined. I
don't know what is urgent and different people have different
definition, but in general I think that should be measured by tx fee in
USD. 0.001USD/byte may be intolerable for many people. (It's about
$0.0001/byte now, and $0.0005/byte when it was $1200/BTC). It's not
difficult to reach this level given the halving and potential bull
market is coming.
Mine is: we should consider a block increase only when minimum market
fees for transactions to be mined (currently zero satoshis) increase
above a high fee (admittedly undefined, but certainly greater than
zero).
As I argued above, it's already too late when things become really
urgent. That will lead to serious market disruption, and the uncertainty
could be very harmful to the development of the bitcoin economy.
Even if it's "urgent", I think we should only increase the maximum if,
at the same time, the new size can be considered safe
mining-centralization-wise (unfortunately we don't have any metric to
measure that nor enough tools to realistically simulate different
sizes in different network topologies at the moment). But once we have
them, the next discussion will be much simpler, so I don't see the
need for block size maximum that changes over time (neither
exponentially nor linearly).
Would you agree with me that mining centralization should be the most
important criterion when changing the block size maximum rule rather
than the level of minimum fees?
As I said above, strictly limiting the block size may have little effect
on mining centralization (because block size at this level is not a
determining factor), while it may seriously suppress the utility.
I'm all for mining decentralization but block size is just not the right
way to improve the situation.
If the community can't agree on this, I'm afraid there will be a
schism hardfork eventually. Another possibility is that those who
aren't concerned with mining centralization start their own altcoin
(centralizedcoin? ), maybe a spinoff [
https://bitcointalk.org/index.php?topic=563972.0 ] if they want to
keep Bitcoin's utxo at the moment of the separation.
But if the community agrees with this and just disagrees on the
maximum block size consensus rule having any effect on mining
centralization (like Gavin and I disagree), we should calm down and
use scientific processes to find out what the relation between the two
actually is (if there's any relation at all).
Would you agree with me on this?
I agree with you, but the balance between centralization and utility is
also important. (and I believe the difference between 1MB and 8MB is
tolerable, at least I must keep my full node running at this level)
I also have an idea to have a "decentralizedcoin", with very small
blocks and everyone could mine with a CPU. That would be interesting if
it is backed by famous devs in this area and is not
yet-another-scamcoin.
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