How to speed up python networking?

Question

I am finding python networking slow. I have a server (written in C). I tested it with my client (python). I could reach `2MB/s`. It worried me so I checked this: host1 (client): `cat some_big_file | nc host2 9999` host2 (server): `nc -l 0.0.0.0 9999 | pv > /dev/null` I reached something around 120MB/s (1Gb). The server is not a bottleneck, we use it on production and it can handle more. But to be sure I copied simple python `gevent` server for tests. It looks like this: ``` #!/usr/bin/env python from gevent.server import StreamServer from gevent.pool import Pool def handle(socket, address): while True: print socket.recv(1024) pool = Pool(20000) server = StreamServer(('0.0.0.0', 9999), handle, spawn=pool) server.serve_forever() ``` Next measure is to send from `nc (host1)` to `gserver (host2)`. host1: `cat some_big_file | nc host2 9999` host2: `./gserver.py | pv > /dev/null` The output on `host2`: `[ 101MB/s]`. Not bad. But still, when I use my python client, it's slow. I switched clie…

Accepted Answer

The problem is not really that networking is slow - python function calls have a lot of overhead. If you call `connection.send` a lot of times, you're going to have a lot of wasted CPU time on function calls.

On my computer, your program averages about 35 MB/s. Doing a simple modification, I get 450 MB/s:

```
#...
c.send('xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'*10+'
')
```

I could reach speeds over 1GB/s, by sending even more data at once.

If you want to maximize your throughput, you should send as much data as possible in a single call to `send`. A simple way of doing it would be concatenating several strings before sending the final result. If you do this, remember python strings are immutable, so successive string concatenation (with large strings) is slow. You'll want to use a `bytearray` instead.

How to speed up python networking?

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