Add file takes long time and concurrency in ipfs

[beyonderyue]

Version information:

go-ipfs version: 0.4.15-
Repo version: 6
System version: amd64/linux
Golang version: go1.10.2

Type:

Enhancement

Description:

blocks: 15GB
datastore: 860KB
When I add a small file using ipfs add or java-ipfs-api, it will take over 20 seconds.
Why it take so long time?

And does ipfs support add files simutanneously?
When I open 100 threads to add different files to ipfs, it will take long time.
Can you give me some advice when using ipfs in concurrency situation?

[colortigerhu]

you should update Type from "Enhancement" to "Bug"

[Stebalien]

This looks like #5221.