SSD vs. tmpfs speed

I made a tmpfs filesystem in my home directory on Ubuntu using this command:

$ mount -t tmpfs -o size=1G,nr_inodes=10k,mode=0777 tmpfs space
$ df -h space .
File system                  Size    Used Avail. Avail% Mounted at
tmpfs                        1,0G    100M  925M   10%   /home/user/space
/dev/mapper/ubuntu--vg-root  914G    373G  495G   43%   /

Then I wrote this Python program:

#!/usr/bin/env python3

import time
import pickle


def f(fn):
    start = time.time()
    with open(fn, "rb") as fh:
        data = pickle.load(fh)
    end = time.time()
    print(str(end - start) + "s")
    return data


obj = list(map(str, range(10 * 1024 * 1024)))  # approx. 100M


def l(fn):
    with open(fn, "wb") as fh:
        pickle.dump(obj, fh)


print("Dump obj.pkl")
l("obj.pkl")
print("Dump space/obj.pkl")
l("space/obj.pkl")

_ = f("obj.pkl")
_ = f("space/obj.pkl")

The result:

Dump obj.pkl
Dump space/obj.pkl
0.6715312004089355s
0.6940639019012451s

I am confused about this result. Isn’t the tmpfs a file system based on RAM and isn’t RAM supposed to be notably faster than any hard disk, including SSDs?

Furthermore, I noticed that this program is using over 15GB of RAM when I increase the target file size to approx. 1 GB.

How can this be explained?

The background of this experiment is that I am trying to find alternative caching locations to the hard disk and Redis that are faster and available to multiple worker processes.

Answer

Answer flowing on from comments:

The time elapsed seems to be a python thing, rather than the media of choice.

In a similar set-up (SSD vs tmpfs) using OS commands on Linux the speed difference in writing a 100MB file is notable:

To tmpfs:

$ time dd if=/dev/zero of=space/test.img bs=1048576 count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB, 100 MiB) copied, 0.0231555 s, 4.5 GB/s

real    0m0.030s
user    0m0.000s
sys 0m0.030s

To SSD:

$ time dd if=/dev/zero of=test.img bs=1048576 count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB, 100 MiB) copied, 0.165582 s, 633 MB/s

real    0m0.178s
user    0m0.000s
sys 0m0.060s