[Varnish] #1754: n_objecthead increase just before oomkill

[Varnish]

#1754: n_objecthead increase just before oomkill
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 Reporter:  lkarsten  |      Owner:
     Type:  defect    |     Status:  new
 Priority:  normal    |  Milestone:
Component:  varnishd  |    Version:  trunk
 Severity:  normal    |   Keywords:
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 In 4.0.3 we've seen on some occasions that systems running with long TTLs
 + LRU to clean up, with storage tuned to size of physical memory, have
 been subject to the out of memory handling (oomkiller) in Linux.

 A rise in n_objecthead, not correlated with n_object or n_objectcore, was
 seen in the hours before on some varnishstat plots.

 Assumption that something starts to leak that is not accounted as normal
 storage, and the system (tuned just to the edge of storage) goes over the
 safe limit after a while.

 We don't have the full picture here, making this ticket to have somewhere
 to keep it.

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Ticket URL: <https://www.varnish-cache.org/trac/ticket/1754>
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