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So much fun it is to have multiple servers with 1.5 TB of ram slowly fill up with negative cache dentries to the point that the server kernel finally decides th

So much fun it is to have multiple servers with 1.5 TB of ram slowly fill up with negative cache dentries to the point that the server kernel finally decides that memory pressure is a thing and purges the negative entries all at once - which results in the server being locked up and unresponsive for about ~3 minutes. Oh yeah, and no tunables to control the negative dentry specific behavior.

throwaway2048 5y ago
In general the linux kernel seems extremely badly behaved under ram pressure, see how it reacts to swapping.
- alyandon 5y ago
  It wasn't even actual ram pressure - there was ~500 GB of unused ram but something like 800 GB or so of negative cache dentries. So, it was over some threshold that the kernel decided it was time to start reclaiming all those entries and locked up the entire server while it was doing so. Madness.