Based on some simple testing done with a few combinations of cache
sizes, it seems that the block cache has grown in importance compared to
the where we were before changing on-disk format and adding a lot of
other point caches.
With these settings, there's roughly a 15% performance increase when
processing blocks in the 18M range over the status quo while memory
usage decreases by more than 1gb!
Only a few values were tested so there's certainly more to do here but
this change sets up a better baseline for any future optimizations.
In particular, since the initial defaults were chosen root vertex id:s
were introduced as key prefixes meaning that storage for each account
will be grouped together and thus it becomes more likely that a block
loaded from disk will be hit multiple times - this seems to give the
block cache an edge over the row cache, specially when traversing the
storage trie.
* creating a seq from a table that holds lots of changes means copying
all data into the table - this can be several GB of data while syncing
blocks
* nim fails to optimize the moving of the `WidthFirstForest` - the real
solution is to not construct a `wff` to begin with, but this PR provides
relief while that is being worked on
This spike fix allows us to bump the rocksdb cache by another 2 GB and
still have a significantly lower peak memory usage during sync.
When processing long ranges of blocks, the account cache grows unbounded
which cause huge memory spikes.
Here, we move the cache to a second-level cache after each block - the
second-level cache is cleared on the next block after that which creates
a simple LRU effect.
There's a small performance cost of course, though overall the freed-up
memory can now be reassigned to the rocksdb row cache which not only
makes up for the loss but overall leads to a performance increase.
The bump to 2gb of rocksdb row cache here needs more testing but is
slightly less and loosely basedy on the savings from this PR and the
circular ref fix in #2408 - another way to phrase this is that it's
better to give rocksdb more breathing room than let the memory sit
unused until circular ref collection happens ;)
These options are there mainly to drive experiments, and are therefore
hidden.
One thing that this PR brings in is an initial set of caches and buffers for rocksdb - the set that I've been using during various performance tests to get to a viable baseline performance level.
Jacek Sieka