Performance degradation on LRU nuking

Nils Goroll slink at
Tue Sep 1 14:01:09 UTC 2020

On 01/09/2020 15:52, Ameya Prabhu wrote:
> We are seeing performance issues with Varnish’s file storage when the storage
> reaches its capacity and Varnish starts LRU nuking. As soon as varnish begins
> nuking objects, the number of worker threads(MAIN.threads) starts increasing
> until it hits the limit(thread_pool_max) and remains pinned on the
> thread_pool_max. This then leads to incoming requests getting queued. 
some 12-18 months back, I made an effort to prototype improvements to the LRU
nuking, but never reached an anything mature enough for a pull request.

That said, in my case I used malloc storage and the issue was high lock
contention. As you mention you are using file storage, I would suspect that IO
performance could be the bottleneck.

There is no magic knob I would be aware of, other than using more RAM and faster IO.


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