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To: Matt Corallo <lf-lists@mattcorallo.com>,
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Subject: Re: [bitcoin-dev] [BIP Draft] Datastream compression of Blocks and
Transactions
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On 30/11/2015 9:28 PM, Matt Corallo wrote:
> I'm really not a fan of this at all. To start with, adding a compression library that is directly accessible to the network on financial software is a really, really scary idea.
Why scary? LZO has no current security issues, and it will be
configureable by each node operator so it can be turned off completely
if needed or desired.
> If there were a massive improvement, I'd find it acceptable, but the improvement you've shown really isn't all that much.
Why is 15% at the low end, to 27% at the high end not good? It sounds
like a very good boost.
> The numbers you recently posted show it improving the very beginning of IBD somewhat over high-latency connections, but if we're throughput-limited after the very beginning of IBD, we should fix that, not compress the blocks.
I only did the compression up to the 200,000 block to better isolate the
transmission of data from the post processing of blocks and determine
whether the compressing of data was adding to much to the total
transmission time.
I think it's clear from the data that as the data (blocks, transactions)
increase in size that (1) they compress better and (2) they have a
bigger and positive impact on improving performance when compressed.
> Additionally, I'd be very surprised if this had any significant effect on the speed at which new blocks traverse the network (do you have any simulations or other thoughts on this?).
From the table below, at 120000 blocks the time to sync the chain was
roughly the same for compressed vs. uncompressed however after that
point as block sizes start increasing, all compression libraries
peformed much faster than uncompressed. The data provided in this
testing clearly shows that as block size increases, the performance
improvement by compressing data also increases.
TABLE 5:
Results shown in seconds with 60ms of induced latency
Num blks sync'd Uncmp Zlib-1 Zlib-6 LZO1x-1 LZO1x-999
--------------- ----- ------ ------ ------- ---------
120000 3226 3416 3397 3266 3302
130000 4010 3983 3773 3625 3703
140000 4914 4503 4292 4127 4287
150000 5806 4928 4719 4529 4821
160000 6674 5249 5164 4840 5314
170000 7563 5603 5669 5289 6002
180000 8477 6054 6268 5858 6638
190000 9843 7085 7278 6868 7679
200000 11338 8215 8433 8044 8795
As far as, what happens after the block is received, then obviously
compression isn't going to help in post processing and validating the
block, but in the pure transmission of the object it most certainly and
logically does and in a fairly direct proportion to the file size (a
file that is 20% smaller will be transmited "at least" 20% faster, you
can use any data transfer time calculator
<http://www.calctool.org/CALC/prof/computing/transfer_time> for that).
The only issue, that I can see that required testing was to show how
much compression there would be, and how much time the compression of
the data would add to the sending of the data.
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<div class="moz-cite-prefix"><br>
On 30/11/2015 9:28 PM, Matt Corallo wrote:<br>
</div>
<blockquote
cite="mid:90EF4E6C-9A71-4A35-A938-EAFC1A24DD24@mattcorallo.com"
type="cite">
<pre wrap="">I'm really not a fan of this at all. To start with, adding a compression library that is directly accessible to the network on financial software is a really, really scary idea. </pre>
</blockquote>
Why scary? LZO has no current security issues, and it will be
configureable by each node operator so it can be turned off
completely if needed or desired. <br>
<blockquote
cite="mid:90EF4E6C-9A71-4A35-A938-EAFC1A24DD24@mattcorallo.com"
type="cite">
<pre wrap="">If there were a massive improvement, I'd find it acceptable, but the improvement you've shown really isn't all that much.</pre>
</blockquote>
Why is 15% at the low end, to 27% at the high end not good? It
sounds like a very good boost. <br>
<blockquote
cite="mid:90EF4E6C-9A71-4A35-A938-EAFC1A24DD24@mattcorallo.com"
type="cite">
<pre wrap=""> The numbers you recently posted show it improving the very beginning of IBD somewhat over high-latency connections, but if we're throughput-limited after the very beginning of IBD, we should fix that, not compress the blocks. </pre>
</blockquote>
I only did the compression up to the 200,000 block to better isolate
the transmission of data from the post processing of blocks and
determine whether the compressing of data was adding to much to the
total transmission time.<br>
<br>
I think it's clear from the data that as the data (blocks,
transactions) increase in size that (1) they compress better and (2)
they have a bigger and positive impact on improving performance when
compressed.<br>
<br>
<blockquote
cite="mid:90EF4E6C-9A71-4A35-A938-EAFC1A24DD24@mattcorallo.com"
type="cite">
<pre wrap="">Additionally, I'd be very surprised if this had any significant effect on the speed at which new blocks traverse the network (do you have any simulations or other thoughts on this?).
</pre>
</blockquote>
From the table below, at 120000 blocks the time to sync the chain
was roughly the same for compressed vs. uncompressed however after
that point as block sizes start increasing, all compression
libraries peformed much faster than uncompressed. The data provided
in this testing clearly shows that as block size increases, the
performance improvement by compressing data also increases.<br>
<br>
TABLE 5:<br>
Results shown in seconds with 60ms of induced latency<br>
Num blks sync'd Uncmp Zlib-1 Zlib-6 LZO1x-1 LZO1x-999<br>
--------------- ----- ------ ------ ------- --------- <br>
120000 3226 3416 3397 3266 3302<br>
130000 4010 3983 3773 3625 3703<br>
140000 4914 4503 4292 4127 4287<br>
150000 5806 4928 4719 4529 4821<br>
160000 6674 5249 5164 4840 5314<br>
170000 7563 5603 5669 5289 6002<br>
180000 8477 6054 6268 5858 6638<br>
190000 9843 7085 7278 6868 7679<br>
200000 11338 8215 8433 8044 8795<br>
<br>
<br>
As far as, what happens after the block is received, then obviously
compression isn't going to help in post processing and validating
the block, but in the pure transmission of the object it most
certainly and logically does and in a fairly direct proportion to
the file size (a file that is 20% smaller will be transmited "at
least" 20% faster, you can use any data transfer time <a
href="http://www.calctool.org/CALC/prof/computing/transfer_time">calculator</a>
for that). The only issue, that I can see that required testing was
to show how much compression there would be, and how much time the
compression of the data would add to the sending of the data. <br>
<br>
<br>
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