Wednesday, July 28, 2021

Fun with Linux I/O Stats

A discussion with my wife about random I/O and how I’m not sure NVMe would make a measurable difference to my life got me to wondering, how much I/O does a modern Linux system perform during bootup?

I have Ubuntu Studio 21.04 installed on hardware, and it issues around 18,800 read requests for 1.5 million sectors to boot to the desktop (and to start Alacritty to cat /proc/diskstats.)

I then installed Linux Mint 20.2 Cinnamon Edition and Xubuntu 21.04 in virtual machines, and ran similar tests, using their native terminal emulators.  Mint issues around 19,000 read requests for 1.2 million sectors.

Xubuntu issues about 20,500 read requests for 1.4 million sectors.

To be fair, Xubuntu does win the “least RAM used” contest.  After checking the diskstats file, free -m indicated 428 MB in use on Xubuntu, 547 MB on Mint Cinnamon, and 637 MB on Ubuntu Studio.

Xubuntu was a surprising disappointment; besides issuing the most read requests to boot up, it lacked in features.  The keyboard layout wouldn’t work.  I also discovered along the way that its live environment can’t control the backlight on a “late 2012” iMac, unlike mainline Ubuntu.

(Originally, I was hoping to get the info from the live environment, but the automatic media check dashed my hopes.)

Based on the information so far, I don’t have any new evidence that NVMe would be much of a performance boost.  Sure, the numbers are bigger, but I’m looking for a life-altering wow factor, like going from HDD to SSD was.

Added 2021-07-29: Synthetic benchmarks don’t seem to add up to real-world performance.  (As usual!) It makes great gains in CrystalDiskMark, but actual tasks can turn game load times from 36 to 30 seconds, or a 1.8 GB Photoshop file from 18 to 11 seconds.  To be fair, that seems to be on the order of magnitude of Linux booting up, which I’m largely interested in as the most massive task I tend to put my hardware to.  It’s not like the SATA SSD is so slow that my mind wanders while waiting for Firefox to load.

For something that’s marketed as if it’s five to ten times faster, that’s a disappointingly weak effect in practice.  And worse, a PCIe 4.0 drive can cost more than double of what the SATA variant does, with the same manufacturer and capacity.  For that kind of money, I want the performance to double across the board.  But I’m getting older, wiser, and grumpier.

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