Is vm.extra_free_kbytes available in Red Hat Enterprise Linux?

Solution Unverified - Updated -


This patch was proposed for the upstream kernel by Rik van Riel of Red Hat in 2011:


This parameter tells the VM to keep extra free memory between the threshold
where background reclaim (kswapd) kicks in, and the threshold where direct
reclaim (by allocating processes) kicks in.

This is useful for workloads that require low latency memory allocations
and have a bounded burstiness in memory allocations, for example a
realtime application that receives and transmits network traffic
(causing in-kernel memory allocations) with a maximum total message burst
size of 200MB may need 200MB of extra free memory to avoid direct reclaim
related latencies.


  • Red Hat Enterprise Linux 7 and later version
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 5

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