Is kernel oplocks = yes a good default?
ambi at samba.org
Wed Apr 11 07:25:59 MDT 2012
I was wondering why Samba servers running on Linux are not giving out
Level II oplocks by default and thus cause performance degradation for
Digging into that, I discovered that this due to "kernel oplocks" set to
yes by default and on the two platforms that have kernel oplock support
code for (Linux and IRIX), level 2 oplocks are not supported by the
kernel. (OneFS is the only platform that has support for them).
Another bad thing is that kernel oplocks is a global parameter. So if an
admin is interested in getting NFS/shell interop for just a certain
share, (s)he cannot turn them off for the other shares to get better
performance from those.
I have worked on a patchset that converts the parameter into a share
option that will allow for more fine-grained configuration.
Please have a look at it.
It makes the raw.oplocks test pass when using kernel oplocks = no for
just the share to be tested.
Additionally, I would like to question the current default value of
kernel oplocks: we shouldn't cut off our users from the performance
benefits of level II oplocks on one of our major platforms by default.
I can update the patchset to also flip the default if this is considered
to be a good idea.
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