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FAQ

How do I read an oracleGeneral trace, and how do I convert a csv trace into one?

The oracleGeneral trace is a binary format, so it cannot be read as a text file. Each request is the following struct:

struct {
    uint32_t clock_time;
    uint64_t obj_id;
    uint32_t obj_size;
    int64_t next_access_vtime;  // -1 if there is no next access
};
  • Read the trace: use tracePrint to print the trace as plain text. It is built into bin/ alongside cachesim. 
    ./bin/tracePrint ../data/cloudPhysicsIO.oracleGeneral.bin oracleGeneral
  • Convert a csv trace: use traceConv. See quickstart_traceUtils.md, or run ./bin/traceConv --help. 
    ./bin/traceConv ../data/cloudPhysicsIO.csv csv \
    -t "time-col=2,obj-id-col=5,obj-size-col=4,obj-id-is-num=1" \
    --output-format=oracleGeneral

oracleGeneral traces are usually stored zstd-compressed, and libCacheSim reads them without decompressing first.

What are the units in a trace?

In the sample cloudPhysicsIO.csv, time is in seconds and object size is in bytes.

next_access_vtime is a logical time: the 1-based request index at which this object is next requested — an absolute position in the trace, not the distance to it — or -1 when the object is never accessed again. Algorithms subtract the current request count themselves, so encoding a distance here silently changes eviction order. In cloudPhysicsIO.oracleGeneral.bin, for instance, request 7 stores 19 and that object is next seen at request 19. Algorithms that need future information, such as Belady and BeladySize, rely on it, which is why they only work on oracle traces.

Object ids are hashed unless the reader is told they are already numeric. Pass obj-id-is-num=true in --trace-type-params when the id column holds numbers — cachesim stops with an error if you leave it out on such a trace.

Why does cachesim say "do not support algorithm X"?

Some algorithms are behind an optional build flag because they pull in extra dependencies: GLCache (-DENABLE_GLCACHE=ON), LRB (-DENABLE_LRB=ON), and 3LCache (-DENABLE_3L_CACHE=ON). Rebuild with the relevant flag to enable them. See the README for the full list.

Where can I get larger traces?

The traces in data/ are samples and are far too small to compare miss ratios between algorithms. We maintain a list of open-source cache datasets at cacheMon/cache_dataset.

More questions? Check the documentation index, search the issue tracker, or ask in Discussions.