Memory usage exceeds expectations!

[biuboombiuboom]

I am using vector to consume messages from Kafka and write them to ClickHouse.

The buffer size is 40k, and the batch size is 80k.

800k kafka message size is approximately 700MB, and the converted ClickHouse request size is around 1GB.
But the machine monitoring shows peak memory usage of 30GB, which is about double the expected usage.

config

[sources.in]
session_timeout_ms = 120000
type = "kafka"
bootstrap_servers = "#"
group_id = "flume-clickhouse-event"
topics = ["#"]
librdkafka_options = { "auto.offset.reset" = "latest", "fetch.min.bytes" = "10240" }

[transforms.balance]
type = "remap"
inputs = ["in"]
drop_on_error = true
source = '.route_id=random_int(0,3)'

[transforms.route]
type = "route"
inputs = ["balance"]
reroute_unmatched = false
route.first = '.route_id==0'
route.second = '.route_id==1'
route.third = '.route_id==2'


[sinks.out-clickhouse-1]
type = "clickhouse"
inputs = ["route.first"]
compression = "none"
endpoint = "http://localhost:8125"
database = "mytable"
batch.max_events = 800000
batch.max_bytes = 16106127360
batch.timeout_secs = 120
request.timeout_secs = 120
request.adaptive_concurrency.initial_concurrency=4
# request.adaptive_concurrency.max_concurrency_limit=4
buffer.type = "memory"
buffer.max_events = 400000
buffer.when_full = "block"

[sinks.out-clickhouse-2]
type = "clickhouse"
inputs = ["route.second"]
compression = "none"
endpoint = "http://localhost:8125"
database = "mytable"

batch.max_events = 800000
batch.max_bytes = 16106127360
batch.timeout_secs = 120

request.timeout_secs = 120
request.adaptive_concurrency.initial_concurrency=4
# request.adaptive_concurrency.max_concurrency_limit=4

buffer.type = "memory"
buffer.max_events = 400000
buffer.when_full = "block"

[sinks.out-clickhouse-3]
type = "clickhouse"
inputs = ["route.third"]
compression = "none"
endpoint = "http://localhost:8125"
database = "mytable"
batch.max_events = 800000
batch.max_bytes = 16106127360
batch.timeout_secs = 120
request.timeout_secs = 120
request.adaptive_concurrency.initial_concurrency=4
buffer.type = "memory"
buffer.max_events = 400000
buffer.when_full = "block"

memory monitor