[PATCH 0/1] NFS: pnfs: cache data server entries for a short grace period

[Lei Lei2 Yin]

Hi,

This patch keeps pNFS data server cache entries alive for a short grace
period after the last reference is dropped.

Today, a data server cache entry is destroyed immediately when the last
reference goes away. In open/close-heavy workloads, that can lead to
repeated teardown and re-creation of the same data server cache entry
when the same data server is reused again shortly afterwards.

This patch defers destruction for a short time and reuses the existing
entry if the same data server is looked up again before the timeout
expires. Since destruction is deferred, it also reaps scheduled destroy
work during netns teardown.

In testing with workloads that repeatedly open and close files, the
additional read/write latency associated with repeated data server cache
churn dropped from a few milliseconds, and in some runs tens of
milliseconds, to under 100 microseconds.

Thanks,
Lei Yin

Lei Yin (1):
  NFS: pnfs: cache data server entries for a short grace period