a61907e5d9c1988eb1e018cae5831d6b94f4da7f doc: explain swapping in `reduce-memory.md` (Lőrinc)
Pull request description:
### Problem
Sustained [heavy swapping](https://en.wikipedia.org/wiki/Thrashing_(computer_science)) can grind execution to a halt, but today users get no direct warning from the node when this happens, and this caveat is not documented.
### Fix
We can’t easily detect heavy swap pressure in a reliable, cross-platform way, but we can document what swapping is and why it can severely degrade IBD performance.
---
Note: An earlier version of this PR attempted to detect and warn on heavy swapping (Linux-only), but it was changed to documentation based on review feedback.
ACKs for top commit:
ajtowns:
utACK a61907e5d9c1988eb1e018cae5831d6b94f4da7f
sedited:
ACK a61907e5d9c1988eb1e018cae5831d6b94f4da7f
Tree-SHA512: b21c40d07d78d890c19d3a17faad4ab4127688884dc433a1bdb63d18de07628c048227eba2f1258c6b542a71a986d4250f8abf8f8ffe0cda433ce0c8673978d4
Changes to the default mempool allocation size now documented.
Provides users with guidance on the mempool implications of -blocksonly
mode, along with instructions on how to re-enable old behaviour.
When -blocksonly is set to 1, it interacts with the -walletbroadcast
parameter and sets it to 0 if it has not been set already.This behavior
is not captured by the current documentation, which claims that -blocksonly
does not impact any wallet transactions.
Update the max number of outgoing peers from 8 to 10, due to the
addition of two -blocksonly peers.
