Write a kind of spec for my performance monitoring work. Peer review is welcome

doc/README.performance_monitoring

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+	Performance analysis with Firebird.
+	Document version 0.1
+	Created by Nickolay Samofatov
+
+Performance monitoring framework is consisted of 2 parts:
+- Trace API
+- Reference implementation of analysis plugin
+
+
+Trace API.
+
+	Trace API allows to plug a monitoring module into the engine and notify it 
+of processes happening there. List of analysis plugins is specified in 
+firebird.conf parameter TracePlugins. Each trace plugin receives notifications 
+on each database attached as a call of procedure having following signature:
+
+ISC_STATUS trace_attach(ISC_STATUS* status, TraceDatabase* db);
+
+Conceptually db is the database trace interface, but it is implemented as a 
+structure of function pointers and void* object pointer.
+
+Given this interface plugin may install hooks for particular events and receive 
+notifications on them. In fact, set of hooks is also implemented as a structure 
+with function pointers.
+
+See ntrace.h module for definitions of these structures and events supported.
+
+
+Default analysis module.
+
+	Reference implementation of analysis plugin is centered around a concept of 
+performance snapshot. Snapshot detail may vary, but in any case it contains
+information on all activities performed by server during a given period of time,
+possibly in aggregated form. All snapshots may be compared to allow quanititive
+measurements of performance improvements due to various optimization activities
+or changes in user applications and infrastucture.
+
+Snapshot data is collected by trace module in raw form in a binary log file and 
+then may be loaded into a stats database using ntrace utility.
+
+Stored snapshots may contain data on usage of indices, statements executed, 
+their plans and performance counters, IO statistics and other performance data.
+
+Level of detail for information collected is set up in analysis trace module 
+configuration file on per-database basis.
+
+Default analysis module does not have GUI and only provides a database with
+data on server activities and some stored procedures to use and maintain it.
+
+It is expected that third parties develop GUI tools, custom trace modules and 
+statistics tools to statisfy rich client needs.