The BTI partition index trie writer flushes all buffered nodes at the
end of each SSTable via complete_until_depth(0), called from
bti_partition_index_writer_impl::finish(). This is a tight synchronous
loop that writes trie nodes through file_writer::write(), which uses a
buffered output_stream: individual writes that fit in the buffer are
plain memcpy operations returning a ready future, so .get() never
yields. As a result the reactor can stall for several milliseconds on
large SSTables.
The entire call chain runs inside seastar::async() (via
sstable::write_components()), so seastar::thread::maybe_yield() is
safe to call here. Add it at the top of both tight loops:
- complete_until_depth(), which iterates over trie depth
- lay_out_children(), which iterates over child branches per node
Fixes SCYLLADB-1885
Closesscylladb/scylladb#29798
(cherry picked from commit d0813769ec)
Closesscylladb/scylladb#29810Closesscylladb/scylladb#29816
d33fb5159a