janwas
37663d86fb
file_cache: avoid caching 0-length files (prevents div by 0) adts: bit more defensiveness against size=0 trace: now use "dividers" in the trace file instead of relying on monotony property of the get_time source. this avoids incorrectly splitting the trace into runs when time is actually not monotonous (which would cause lots of warnings), e.g. due to debugger. in the process, changed interface to return (most-recent first) runs, instead of only the raw unsorted entries. This was SVN commit r3832.
99 lines
3.0 KiB
C
99 lines
3.0 KiB
C
/**
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* =========================================================================
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* File : trace.h
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* Project : 0 A.D.
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* Description : allows recording and 'playing back' a sequence of
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* : I/Os - useful for benchmarking and archive builder.
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*
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* @author Jan.Wassenberg@stud.uni-karlsruhe.de
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* =========================================================================
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*/
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/*
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* Copyright (c) 2006 Jan Wassenberg
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*
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* Redistribution and/or modification are also permitted under the
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* terms of the GNU General Public License as published by the
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* Free Software Foundation (version 2 or later, at your option).
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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*/
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#ifndef TRACE_H__
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#define TRACE_H__
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extern void trace_enable(bool want_enabled);
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extern void trace_shutdown();
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extern void trace_notify_io(const char* P_fn, size_t size, uint flags);
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extern void trace_notify_free(const char* P_fn, size_t size);
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// TraceEntry operation type.
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// note: rather than only a list of accessed files, we also need to
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// know the application's behavior WRT caching (e.g. when it releases
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// cached buffers). this is necessary so that our simulation can
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// yield the same behavior.
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enum TraceOp
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{
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TO_IO,
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TO_FREE,
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};
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// stores one event that is relevant for file IO / caching.
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//
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// size-optimized a bit since these are all kept in memory
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// (to prevent trace file writes from affecting other IOs)
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struct TraceEntry
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{
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// note: float instead of double for nice 16 byte struct size
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float timestamp; // returned by get_time before operation starts
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const char* atom_fn; // path+name of affected file
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// rationale: store size in the trace because other applications
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// that use this trace format but not our IO code wouldn't know
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// size (since they cannot retrieve the file info given atom_fn).
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size_t size; // of IO (usually the entire file)
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uint op : 8; // operation - see TraceOp
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uint flags : 24; // misc, e.g. file_io flags.
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};
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struct TraceRun
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{
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const TraceEntry* ents;
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size_t num_ents;
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};
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struct Trace
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{
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// most recent first! (see rationale in source)
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const TraceRun* runs;
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size_t num_runs;
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size_t total_ents;
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};
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extern void trace_get(Trace* t);
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extern LibError trace_write_to_file(const char* trace_filename);
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extern LibError trace_read_from_file(const char* trace_filename, Trace* t);
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extern void trace_gen_random(size_t num_entries);
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// simulate carrying out the entry's TraceOp to determine
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// whether this IO would be satisfied by the file_buf cache.
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extern bool trace_entry_causes_io(const TraceEntry* ent);
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enum TraceRunFlags
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{
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TRF_SYNC_TO_TIMESTAMP = 1
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};
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// carry out all operations specified in the trace.
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// if flags&TRF_SYNC_TO_TIMESTAMP, waits until timestamp for each event is
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// reached; otherwise, they are run as fast as possible.
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extern LibError trace_run(const char* trace_filename, uint flags = 0);
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#endif // #ifndef TRACE_H__
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