On 12/31/2015 06:36 AM, Amit Kapila wrote:
Going further on this work, I have written a patch for separating the
tranches for extensions.  The basic idea is to expose two new API's,
first to request a new tranche and second to assign a lock from that
RequestAddinLWLockTranche(const char *tranche_name, int num_lwlocks)
will be used by extensions to request a new tranche with specified number
of locks, this will be used instead of current API RequestAddinLWLocks().
We need to remember this information for each extension and then
during startup we need to create separate tranches and still have locks
for extensions in the MainLWLockArray such that the base for each
tranche will point to the locks corresponding to that tranche.  As for
each proc/backend, we need to register the tranche separately, the
information of newly formed tranches needs to be passed to backends
via save/restore_backend_variables mechanism for EXEC_BACKEND
LWLock *LWLockAssignFromTranche(const char *tranche_name) will
assign a lock for the specified tranche.  This also ensures that no
more than requested number of LWLocks can be assigned from a
specified tranche.

Also I have retained NUM_USER_DEFINED_LWLOCKS in
MainLWLockArray so that if any extensions want to assign a LWLock
after startup, it can be used from this pool.  The tranche for such locks
will be reported as main.

This is based on the suggestions by Robert in the mail:


+1 for the idea.

However, RequestAddinLWLocks and LWLockAssign are used by extensions outside of the main tree, so I think it would be better to deprecate the methods for starters with a log statement.

NUM_USER_DEFINED_LWLOCKS aren't enough in many cases, so the existing functionality needs to be maintained during the deprecation period.

If extensions needs to upgrade to the new API I think LWLockAssign should be removed.

doc/src/sgml/xfunc.sgml needs an update on how the new API should be used.

Best regards,

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