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From Justin Erenkrantz <jerenkra...@ebuilt.com>
Subject SDBM locking...
Date Sun, 13 May 2001 02:48:02 GMT
This message is really directed towards Bill and Greg...

What is the status of the SDBM locking code?  I know that Bill
committed some stuff to implement reference counting and other 
things.  I'm not sure if he finished that commit or not (I think so).

In my "tests" (if you could call them that), the mod_mbox code is 
spending a lot of time obtaining and releasing file locks related to the
SDBM code (besides writing to the network).  Is there any plan to 
implement either a fast path without locking or to somehow address the 
locking speed?

Wouldn't it be possible to just hold the file lock for the duration that
we have the SDBM open rather than obtaining and releasing it at every
call?  So, if you open with an exclusive lock, you get an exclusive file
lock on the DBM until you close it.  The file handle is open at all points,
so I'm not sure what the logic is for getting and releasing the file
lock at each call - the cache is almost useless because it'll be
invalidated all the time.  

If a shared lock on that file exists, exclusive locks will block until
the shared locks are released (shared locks should not be affected), and
if an exclusive lock is held by someone, everyone waits until it is
released.

Or, is there a drawback to this that I am not seeing?  -- justin


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