In defense of swap: common misconceptions (2018)
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HN comment order(The article is from 2018.) I think the article is strongly from the point of view of what to do "in production". If you have a bunch of servers with known specialized workloads, I can believe that enabling swap is good for efficiency. You can run more tasks and get closer to the memory limit while remaining safe. Coming from a Facebook employee, this makes sense. However, for individual development machines, the pragmatic situation is completely different. The truth is…
In my experience, a misbehaving linux system that's out of RAM and has swap to spare will be unusably slow. The process of switching to a tty, logging in, and killing whatever the offending process is can easily take a good 15 minutes. Xorg will just freeze. Oh, and hopefully you know what process it is, else good luck running `top`. Until this is fixed, I'll just keep running my systems with very small amounts of swap (say, 512MB in…
On my desktop system, most of my problems with swap come from dealing with the aftermath of an out-of-control process eating all my RAM. In this case, the offending program demands memory so quickly that everything from legitimate programs gets swapped out. These programs proceed to run poorly for the next several minutes to an hour depending on usage, since the OS only swaps pages back in once they are referenced, even if there is plenty of free space not…
Swap is still actively harmful if placed on an unsuitable device. A few days ago, I got a complaint about slow ops in a Ceph cluster, and one of the Ceph OSDs spent quite a visible amount of time in response to a simple "ceph tell osd.13 ops" query that is a natural first step when debugging slow ops. Upon investigation, it was found that one of the nodes had a significantly higher load average (50) vs others (14-18). In…
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- Breakout years
- 5
- Total points
- 611
- Total comments
- 630
100+ points or 50+ comments
reference only — not used in Hall rules or ranking
reference only — not used in Hall rules or ranking
Every submission
| Date | Title as submitted | By | Points | Comments |
|---|---|---|---|---|
| 2018-01-09 | In defence of swap: common misconceptions | cdown | 2 | 1 |
| 2018-01-14 | In defence of swap: common misconceptionsFirst breakout | c4urself | 150 | 148 |
| 2020-06-08 | In defence of swap: common misconceptions | rwmj | 68 | 62 |
| 2021-11-09 | In defence of swap: common misconceptions (2018) | 1_player | 8 | 7 |
| 2022-04-20 | In defense of swap: common misconceptions (2018)Hall induction · Best thread | linsomniac | 182 | 165 |
| 2023-11-14 | In defence of swap: common misconceptions | voxadam | 1 | 0 |
| 2024-03-09 | In defense of swap: common misconceptions (2018) | yla92 | 2 | 0 |
| 2024-06-05 | In defence of swap: common misconceptions (2018) | ingve | 82 | 97 |
| 2025-09-21 | In defence of swap: common misconceptions (2018)Latest 20+ point return | jitl | 116 | 150 |