As per https://www.novell.com/support/kb/doc.php?id=7012805
"This message isn't really an error per se, it's more just informational.
There is an environmental variable, TCMALLOC_LARGE_ALLOC_REPORT_THRESHOLD, which by default is set to 1073741824 bytes. ~1GB
So if there is an allocation that is == or exceeds 1GB of memory, this message will be displayed in the ndsd.log.
If there is a great deal of memory in the server, such as greater than 8G - 32GB and/or a fairly large eDirectory database you may see this message more readily. You can just modify the threshold to be greater than the typical alloc that your seeing in the ndsd.log."
I'm not sure this is specifically correct given I'm unaware of the environment you're using, I'd say the explanation can be generalized as a warning that 1GB of memory has been allocated by the running application.
Further info:
https://github.com/gperftools/gperftools/issues/360
Edit: As per the OPS comments, it appears that the same error was produced when allocating 1gb and 21gb so it would be safe to assume that there is a programmatic error that is using all available memory, I would go back and review the code.