When I need to do echo 3 > /proc/sys/vm/drop_caches with a sync beforehand, is it better to use

sync && echo 3 > /proc/sys/vm/drop_caches or

sync ; echo 3 > /proc/sys/vm/drop_caches.

Does it even matter because both commands are safe for the filesystem data? Or might the second version lose data in the process?

  • You only lose performance, not data. – Michael Hampton Dec 14 '15 at 12:39

More like... you shouldn't need to do this at all. What's the root or underlying performance problem you're trying to correct with the drop_caches routine?

For the record, sync ; echo 3 > /proc/sys/vm/drop_caches is fine.

  • I wuld argue that the sync is superfluous as when dropping the cache the system will need to sync the contents to disk anyway. You don't lose data whatever you do. – wurtel Dec 14 '15 at 13:09
  • I stumbled upon this gem while migrating and old system to a VM. There are some long running processes that seem to leak memory over time. – micxer Dec 16 '15 at 8:39

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