Here are the latest results on compression ratios for the first 295,000 blocks, compressionlevel=6. I think there are more than enough datapoints for statistical significance. Results are very much similar to the previous test. I'll work on getting a comparison between how much time savings/loss in time there is when syncing the blockchains: compressed vs uncompressed. Still, I think it's clear that serving up compressed blocks, at least historical blocks, will be of benefit for those that have bandwidth caps on their internet connections. The proposal, so far is fairly simple: 1) compress blocks with some compression library: currently zlib but I can investigate other possiblities 2) As a fall back we need to advertise compression as a service. That way we can turn off compression AND decompression completely if needed. 3) Do the compression at the datastream level in the code. CDataStream is the obvious place. Test Results: range = block size range ubytes = average size of uncompressed blocks cbytes = average size of compressed blocks ctime = average time to compress dtime = average time to decompress cmp_ratio% = compression ratio datapoints = number of datapoints taken range ubytes cbytes ctime dtime cmp_ratio% datapoints 0-250b 215 189 0.001 0.000 12.40 91280 250-500b 438 404 0.001 0.000 7.85 13217 500-1KB 761 701 0.001 0.000 7.86 11434 1KB-10KB 4149 3547 0.001 0.000 14.51 52180 10KB-100KB 41934 32604 0.005 0.001 22.25 82890 100KB-200KB 146303 108080 0.016 0.001 26.13 29886 200KB-300KB 243299 179281 0.025 0.002 26.31 25066 300KB-400KB 344636 266177 0.036 0.003 22.77 4956 400KB-500KB 463201 356862 0.046 0.004 22.96 3167 500KB-600KB 545123 429854 0.056 0.005 21.15 366 600KB-700KB 647736 510931 0.065 0.006 21.12 254 700KB-800KB 746540 587287 0.073 0.008 21.33 294 800KB-900KB 868121 682650 0.087 0.008 21.36 199 900KB-1MB 945747 726307 0.091 0.010 23.20 304 On 10/11/2015 8:46 AM, Jeff Garzik via bitcoin-dev wrote: > Comments: > > 1) cblock seems a reasonable way to extend the protocol. Further > wrapping should probably be done at the stream level. > > 2) zlib has crappy security track record. > > 3) A fallback path to non-compressed is required, should compression > fail or crash. > > 4) Most blocks and transactions have runs of zeroes and/or highly > common bit-patterns, which contributes to useful compression even at > smaller sizes. Peter Ts's most recent numbers bear this out. zlib > has a dictionary (32K?) which works well with repeated patterns such > as those you see with concatenated runs of transactions. > > 5) LZO should provide much better compression, at a cost of CPU > performance and using a less-reviewed, less-field-tested library. > > > > > > On Tue, Nov 10, 2015 at 11:30 AM, Tier Nolan via bitcoin-dev > > wrote: > > > > On Tue, Nov 10, 2015 at 4:11 PM, Peter Tschipper > > wrote: > > There are better ways of sending new blocks, that's certainly > true but for sending historical blocks and seding transactions > I don't think so. This PR is really designed to save > bandwidth and not intended to be a huge performance > improvement in terms of time spent sending. > > > If the main point is for historical data, then sticking to just > blocks is the best plan. > > Since small blocks don't compress well, you could define a > "cblocks" message that handles multiple blocks (just concatenate > the block messages as payload before compression). > > The sending peer could combine blocks so that each cblock is > compressing at least 10kB of block data (or whatever is optimal). > It is probably worth specifying a maximum size for network buffer > reasons (either 1MB or 1 block maximum). > > Similarly, transactions could be combined together and compressed > "ctxs". The inv messages could be modified so that you can > request groups of 10-20 transactions. That would depend on how > much of an improvement compressed transactions would represent. > > More generally, you could define a message which is a compressed > message holder. That is probably to complex to be worth the > effort though. > > > >> >> On Tue, Nov 10, 2015 at 5:40 AM, Johnathan Corgan via >> bitcoin-dev > > wrote: >> >> On Mon, Nov 9, 2015 at 5:58 PM, gladoscc via bitcoin-dev >> > > wrote: >> >> >> I think 25% bandwidth savings is certainly >> considerable, especially for people running full >> nodes in countries like Australia where internet >> bandwidth is lower and there are data caps. >> >> >> ​ This reinforces the idea that such trade-off decisions >> should be be local and negotiated between peers, not a >> required feature of the network P2P.​ >> >> >> -- >> Johnathan Corgan >> Corgan Labs - SDR Training and Development Services >> http://corganlabs.com >> >> _______________________________________________ >> bitcoin-dev mailing list >> bitcoin-dev@lists.linuxfoundation.org >> >> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >> >> >> >> >> _______________________________________________ >> bitcoin-dev mailing list >> bitcoin-dev@lists.linuxfoundation.org >> >> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > > > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > > > > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev