onheapCacheEnabled enormous heap consumption

[Andrey Dolmatov]

We use simple replicated KV cache.
We try to upload 32 000 000 small records <Long, Long> to it (about 6Gb in
data region, persistance disabled). We load data using DataStreamer.

If we set onheapCacheEnabled=false, server node consumes heap about 500 Mb.
If we set onheapCacheEnabled=true, server node consumes heap about 6 Gb.

Why DataStreamer uses heap memory to load data? Why on-heap size is
unlimited (not just 100.000 records)? What default on-heap eviction policy?

<bean class="org.apache.ignite.configuration.CacheConfiguration">

                    <property name="cacheMode" value="REPLICATED"/>
                    <property name="onheapCacheEnabled" value="true"/>
                    <property name="copyOnRead" value="false"/>

Thanks!