Currently mongoimport uses a 4kb buffer for reading data. This can be confirmed by running strace. I provide the data via standard input.

Unfortunately this is a very small buffer size which means there are lots of read() calls. Since I am piping data in from another process this also causes lots of context switches. The Linux pipe buffer size is 64kb. Stdio default buffer size is 4 or 8kb. 4kb in mongoimport is really out of sync.

Since the code is doing bulk reads, please use a larger size. 64kb at least would be nice. I'm supplying over 2GB of data. The net effect of the current value is that imports are slower than they should be.