[Lustre-devel] Reducing amount of glimpses
Oleg.Drokin at Sun.COM
Fri Feb 1 22:26:35 PST 2008
Doing some large scale testing at ORNL, interesting pattern came up.
Suppose we are doing large-scale IOR testing on a shared file.
Some unlucky client does its writing at highest offset (or, at the
was unlucky enough to grab whole-object PW lock).
As other clients do their writes, they would do glimpses first to
find out file
size. Now those glimpses turn into thousands of glimpse requests
to that poor
client. And many of them actually coming in parallel.
So I was thinking - perhaps it would be nice for a
filter_intent_policy() to check
if there are any glimpse requests being in flight to that client
already for that
same lock, and if there are, just wait for the request to return
and use data from
Of course potential caveat here is that we have no way to tell if
the request reached
client by the time we started our processing or not, and so
potentially we might get
size data that is a bit stale, but I wonder if this is critical
enough in our case?
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