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Swap has value. E.g. it lets you have a tmpfs that's larger than your physical RAM. Or you can process memory dumps of a machine larger than yours. Or you can j

Swap has value. E.g. it lets you have a tmpfs that's larger than your physical RAM. Or you can process memory dumps of a machine larger than yours. Or you can just freeze a process group and have it dumped to disk so other processes can use the RAM in the meantime. It can definitely help avoiding the OOM killer. Swap occupancy and swap activity are not the same. The former is fine, the latter should be kept small.

xxs 6y ago
> Or you can process memory dumps of a machine larger than yours. You should be able to that in software anyways - instead of loading to memory entirely, all it has to do is memory map the file dump. About the need to freeze a process (group). I don't quite see how that's useful on a server. On a desktop machine I have never run into such a case where closing the application would not suffice. Is there an example? Last - using the swap pretty much means no disk cache.
- the8472 6y ago
  > You should be able to that in software anyways - instead of loading to memory entirely, all it has to do is memory map the file dump. Should, perhaps. But in practice I have had analyzers gobble up more memory than available. > About the need to freeze a process (group). I don't quite see how that's useful on a server. On a desktop machine I have never run into such a case where closing the application would not suffice. Is there an example? Long-running renderjob, preempted by a higher-priority one. Technically they're resumable so we could stop them and resume the other one later from a snapshot file but that isn't implemented in the current workers. So as long as the machine has enough ram+swap it's easier to freeze the current job and start the higher-priority one. > Last - using the swap pretty much means no disk cache. I don't know all the tunables of the swap subsystem well enough but I have seen swap being used before running out of physical ram. I assume some IO displaced inactive applications.
  - xxs 6y ago
    >analyzers gobble up more memory than available. I can run 128GB, if need be. But yeah if the software is pitiful and poorly implemented. Running on swap is an one-time-option I guess. >so we could stop them and resume the other one later from a snapshot file but that isn't implemented in the current workers. Indeed, this seems like a poor implementation, lacking 'save' function. I have not run into similar cases.

xxs 6y ago

> Or you can process memory dumps of a machine larger than yours. You should be able to that in software anyways - instead of loading to memory entirely, all it has to do is memory map the file dump. About the need to freeze a process (group). I don't quite see how that's useful on a server. On a desktop machine I have never run into such a case where closing the application would not suffice. Is there an example? Last - using the swap pretty much means no disk cache.

the8472 6y ago
> You should be able to that in software anyways - instead of loading to memory entirely, all it has to do is memory map the file dump. Should, perhaps. But in practice I have had analyzers gobble up more memory than available. > About the need to freeze a process (group). I don't quite see how that's useful on a server. On a desktop machine I have never run into such a case where closing the application would not suffice. Is there an example? Long-running renderjob, preempted by a higher-priority one. Technically they're resumable so we could stop them and resume the other one later from a snapshot file but that isn't implemented in the current workers. So as long as the machine has enough ram+swap it's easier to freeze the current job and start the higher-priority one. > Last - using the swap pretty much means no disk cache. I don't know all the tunables of the swap subsystem well enough but I have seen swap being used before running out of physical ram. I assume some IO displaced inactive applications.
- xxs 6y ago
  >analyzers gobble up more memory than available. I can run 128GB, if need be. But yeah if the software is pitiful and poorly implemented. Running on swap is an one-time-option I guess. >so we could stop them and resume the other one later from a snapshot file but that isn't implemented in the current workers. Indeed, this seems like a poor implementation, lacking 'save' function. I have not run into similar cases.