y/metrics.go
func init() {
	NumReads = expvar.NewInt("badger_disk_reads_total")
	NumWrites = expvar.NewInt("badger_disk_writes_total")
	NumBytesRead = expvar.NewInt("badger_read_bytes")
	NumBytesWritten = expvar.NewInt("badger_written_bytes")
	NumLSMGets = expvar.NewMap("badger_lsm_level_gets_total")
	NumLSMBloomHits = expvar.NewMap("badger_lsm_bloom_hits_total")
	NumGets = expvar.NewInt("badger_gets_total")
	NumPuts = expvar.NewInt("badger_puts_total")
	NumBlockedPuts = expvar.NewInt("badger_blocked_puts_total")
	NumMemtableGets = expvar.NewInt("badger_memtable_gets_total")
	LSMSize = expvar.NewMap("badger_lsm_size_bytes")
	VlogSize = expvar.NewMap("badger_vlog_size_bytes")
	PendingWrites = expvar.NewMap("badger_pending_writes_total")
}
func init() {
	NumReads = expvar.NewInt("badger_disk_reads_total")
	NumWrites = expvar.NewInt("badger_disk_writes_total")
	NumBytesRead = expvar.NewInt("badger_read_bytes")
	NumBytesWritten = expvar.NewInt("badger_written_bytes")
	NumLSMGets = expvar.NewMap("badger_lsm_level_gets_total")
	NumLSMBloomHits = expvar.NewMap("badger_lsm_bloom_hits_total")
	NumGets = expvar.NewInt("badger_gets_total")
	NumPuts = expvar.NewInt("badger_puts_total")
	NumBlockedPuts = expvar.NewInt("badger_blocked_puts_total")
	NumMemtableGets = expvar.NewInt("badger_memtable_gets_total")
	LSMSize = expvar.NewMap("badger_lsm_size_bytes")
	VlogSize = expvar.NewMap("badger_vlog_size_bytes")
	PendingWrites = expvar.NewMap("badger_pending_writes_total")
}
// These variables are global and have cumulative values for all kv stores.