this post was submitted on 02 Sep 2023
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ZRAM is insane (www.kernel.org)
submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/[email protected]
 

I got a cheap netbook style laptop for traveling some weeks ago (HP Stream 11" with 4 GB of RAM and a N4120). Didn't expect much more from this hardware than opening a few browser tabs and doing some retro gaming via Steam.

Shared RAM with graphics card means that 3.64 GB of RAM are effectively usable for the OS. This was even too little RAM to open a handful of tabs w/o having tabs being unresponsive for seconds sometimes in a very annoying way. Another thing which made trouble was the Wifi - I guess it went into power saving, was swapped and didn't load fast enough to provide a good experience. (Of course I wasted an hour checking for Wifi drivers/support.)

In short: Even for my low expectations for this laptop it was an underwhelming experience.

First step was to look at my vm.swappiness and set it to 10, which already helped, but still the machine had hiccups and annoying timeouts.

In a last, desperate effort I enabled ZRAM on the laptop... and literally WTF: Saying it is a night and day difference doesn't do the experience justice. Typing this words now on the Stream, which I use exactly the same way as my much more beefy other machines (my next worst computer has 8G of RAM and an Intel Core i3), browsing with 10 open tabs, e-mail client open on another virtual desktop... it is crazy, it makes the Stream fun to use and I use it at home for everything which isn't heavily CPU/IO bound.

What surprised me the most: No hiccups, no timeouts and it even fixed the Wifi issues on this little machine. Didn't expect this would be possible, especially with a N4120 and 3.64 GB of RAM.

In short, my laptop changed from not even reaching my low/realistic expectations to being my favorite technical purchase of the last years, thanks to ZRAM.

Besides making this a ZRAM appreciation post, I really want to spread the word about it. Especially for old hardware and limited RAM situations, IMHO it should be the first thing which comes to mind/is recommended.

Fedora and PopOS use it by default, so it is well tested and should IMHO again, be a default at least for desktop setups.

Give it a try - supposedly it even improved the experience on much more beefy computers for gaming etc.

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[–] [email protected] 1 points 1 year ago (1 children)

No worries, SSDs/sd cards feel different when one grew up with hard disks.

Anecdotal: I am running Raspberrry Pis as home servers for nearly 10 years by now. In the beginning, the sd cards would die within a short period of time. (The first we months, perhaps year?)

I don't know if it is a combination of better tuning of Raspbian and improvements in the sd card technology, but I haven't had a problem with sd cards for at least 9 years now, and at least one Pi is running 24/7 at all times, with lots of IO. (Full disclosure: I am also over provisioning the Pis with big sd cards, to hopefully have better wear leveling.)

With SSDs I personally never experienced hardware failures, OTOH with the dropping prices I bought new ones and replaced the old ones regularly.

What I do nowadays on my machines:

  • ZRAM w/o writeback and a 2nd physical swap device (the physical swap is never touched, even in my low memory devices)
  • I set noatime mount option for all my SSD/sd card to decrease unnecessary reads/write
  • After a hard disk failure many years ago, my important data is backed up to other machines nearly continuously (that's the primary role of the 24/7 Pi)

Don't know if it is helpful, but I would recommend you to use noatime, experiment with ZRAM with zstd and see if your swap is touched at all and use BTRFS for checksums, to detect any trouble with your SSDs early on.

[–] [email protected] 2 points 1 year ago (1 children)

On Raspberry Pi, a larger SD card helps spread out those writes. Alternatively, get a high endurance SD card which is made to handle more writes. Log2ram helps further by journaling logs in RAM then dumps them to your SD card once a day (or at configured interval)

Personally, I just boot my Pi from an SSD in a USB3 enclosure, with log2ram running - best of both worlds.

[–] [email protected] 1 points 1 year ago

Nice, thanks for the hint!