The default database write batch size is increased from 16 MiB to 32 MiB to improve I/O efficiency and performance during UTXO flushes, particularly during Initial Block Download and `assumeutxo` loads.
On systems with slower I/O, a larger batch size reduces overhead from numerous small writes. Measurements show this change provides a modest performance improvement on most hardware during a critical section, with a minimal peak memory increase (approx. 75 MiB on default settings).
This avoids having to rely on implicit casts when passing them to the
various functions allocating the caches.
This also ensures that if the requested amount of db_cache does not fit
in a size_t, it is clamped to the maximum value of a size_t.
Also take this opportunity to make the total amounts of cache in the
chainstate manager a size_t too.
They are not related to the txdb, so a better place for them is the
new kernel and node cache file. Re-use the default amount of kernel
cache for the default node cache.
Carrying non-kernel related fields in the cache sizes for the indexes is
confusing for kernel library users. The cache sizes also are set
currently with magic numbers in bitcoin-chainstate. The comments for the
cache size calculations are also not completely clear.
Solve these things by moving the kernel-specific cache size fields to
their own struct.
This slightly changes the way the cache is allocated if the txindex
and/or blockfilterindex is used. Since they are now given precedence
over the block tree db cache, this results in a bit less cache being
allocated to the block tree db, coinsdb and coins caches. The effect is
negligible though, i.e. cache sizes with default dbcache reported
through the logs are:
master:
Cache configuration:
* Using 2.0 MiB for block index database
* Using 56.0 MiB for transaction index database
* Using 49.0 MiB for basic block filter index database
* Using 8.0 MiB for chain state database
* Using 335.0 MiB for in-memory UTXO set (plus up to 286.1 MiB of unused mempool space)
this branch:
Cache configuration:
* Using 2.0 MiB for block index database
* Using 56.2 MiB for transaction index database
* Using 49.2 MiB for basic block filter index database
* Using 8.0 MiB for chain state database
* Using 334.5 MiB for in-memory UTXO set (plus up to 286.1 MiB of unused mempool space)
