Adding upstream version 1.4.10.upstream/1.4.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 46 insertions, 0 deletions

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+How And Why To Use TDB Tracing
+==============================
+
+You can trace all TDB operations, using TDB_TRACE.  It is not complete
+(error conditions which expect to the logged will not always be traced
+correctly, so you should set up a logging function too), but is designed
+to collect benchmark-style traces to allow us to optimize TDB.
+
+Note: tracing is not efficient, and the trace files are huge: a
+traverse of the database is particularly large!  But they compress very
+well with rzip (http://rzip.samba.org)
+
+How to gather trace files:
+--------------------------
+1) Uncomment /* #define TDB_TRACE 1 */ in tdb_private.h.
+2) Rebuild TDB, and everything that uses it.
+3) Run something.
+
+Your trace files will be called <tdbname>.trace.<pid>.  These files
+will not be overwritten: if the same process reopens the same TDB, an
+error will be logged and tracing will be disabled.
+
+How to replay trace files:
+--------------------------
+1) For benchmarking, remember to rebuild tdb with #define TDB_TRACE commented
+   out again!
+2) Grab the latest "replace_trace.c" from CCAN's tdb module (tools/ dir):
+	http://ccan.ozlabs.org/tarballs/tdb.tar.bz2
+3) Compile up replay_trace, munging as necessary.
+4) Run replay_trace <scratch-tdb-name> <tracefiles>...
+
+If given more than one trace file (presumably from the same tdb)
+replay_trace will try to figure out the dependencies between the operations
+and fire off a child to run each trace.  Occasionally it gets stuck, in
+which case it will add another dependency and retry.  Eventually it will
+give a speed value.
+
+replay_trace can intuit the existence of previous data in the tdb (ie.
+activity prior to the trace(s) supplied) and will prepopulate as
+necessary.
+
+You can run --quiet for straight benchmark results, and -n to run multiple
+times (this saves time, since it need only calculate dependencies once).
+
+Good luck!
+Rusty Russell <rusty@rustcorp.com.au>