* expands number of erasure coding shreds in the last batch in slots (#16484)
Number of parity coding shreds is always less than the number of data
shreds in FEC blocks:
https://github.com/solana-labs/solana/blob/6907a2366/ledger/src/shred.rs#L719
Data shreds are batched in chunks of 32 shreds each:
https://github.com/solana-labs/solana/blob/6907a2366/ledger/src/shred.rs#L714
However the very last batch of data shreds in a slot can be small, in
which case the loss rate can be exacerbated.
This commit expands the number of coding shreds in the last FEC block in
slots to: 64 - number of data shreds; so that FEC blocks are always 64
data and parity coding shreds each.
As a consequence of this, the last FEC block has more parity coding
shreds than data shreds. So for some shred indices we will have a coding
shred but no data shreds. This should not cause any kind of overlapping
FEC blocks as in:
https://github.com/solana-labs/solana/pull/10095
since this is done only for the very last batch in a slot, and the next
slot will reset the shred index.
(cherry picked from commit 37b8587d4e)
# Conflicts:
# core/benches/shredder.rs
# ledger/src/shred.rs
* removes backport merge conflicts
* ignore the flaky test for now
Co-authored-by: behzad nouri <behzadnouri@gmail.com>
* buffers data shreds to make larger erasure coded sets (#15849)
Broadcast stage batches up to 8 entries:
https://github.com/solana-labs/solana/blob/79280b304/core/src/broadcast_stage/broadcast_utils.rs#L26-L29
which will be serialized into some number of shreds and chunked into FEC
sets of at most 32 shreds each:
https://github.com/solana-labs/solana/blob/79280b304/ledger/src/shred.rs#L576-L597
So depending on the size of entries, FEC sets can be small, which may
aggravate loss rate.
For example 16 FEC sets of 2:2 data/code shreds each have higher loss
rate than one 32:32 set.
This commit broadcasts data shreds immediately, but also buffers them
until it has a batch of 32 data shreds, at which point 32 coding shreds
are generated and broadcasted.
(cherry picked from commit 4f82b897bc)
# Conflicts:
# ledger/src/shred.rs
* removes backport merge conflicts
Co-authored-by: behzad nouri <behzadnouri@gmail.com>
