syntax

Documentation

Overview

Package syntax documents the syntax used by benchmark filter and projection expressions.

These expressions work with benchmark data in the Go benchmark format (https://golang.org/design/14313-benchmark-format). Each benchmark result (a line beginning with "Benchmark") consists of several field, including a name, name-based configuration, and file configuration pairs ("key: value" lines).

Keys

Filters and projections share a common set of keys for referring to these fields of a benchmark result:

- ".name" refers to the benchmark name, excluding per-benchmark configuration. For example, the ".name" of the "BenchmarkCopy/size=4k-16" benchmark is "Copy".

- ".fullname" refers to the full benchmark name, including per-benchmark configuration, but excluding the "Benchmark" prefix. For example, the ".fullname" of "BenchmarkCopy/size=4k-16" is "Copy/size=4k-16".

- "/{key}" refers to value of {key} from the benchmark name configuration. For example, the "/size" of "BenchmarkCopy/size=4k-16", is "4k". As a special case, "/gomaxprocs" recognizes both a literal "/gomaxprocs=" in the name, and the "-N" convention. For the above example, "/gomaxprocs" is "16".

- Any name NOT prefixed with "/" or "." refers to the value of a file configuration key. For example, the "testing" package automatically emits a few file configuration keys, including "pkg", "goos", and "goarch", so the projection "pkg" extracts the package path of a benchmark.

- ".config" (only in projections) refers to the all file configuration keys of a benchmark. The value of .config isn't a string like the other fields, but rather a tuple. .config is useful for grouping results by all file configuration keys to avoid grouping together incomparable results. For example, benchstat separates results with different .config into different tables.

- ".unit" (only in filters) refers to individual measurements in a result, such as the "ns/op" measurement. The filter ".unit:ns/op" extracts just the ns/op measurement of a result. This will match both original units (e.g., "ns/op") and tidied units (e.g., "sec/op").

- ".file" refers to the input file provided on the command line (for command-line tools that use benchfmt.Files).

Filters

Filters are boolean expressions that match or exclude benchmark results or individual measurements.

Filters are built from key-value terms:

key:value     - Match if key's value is exactly "value".
key:"value"   - Same, but value is a double-quoted Go string that
                may contain spaces or other special characters.
"key":value   - Keys may also be double-quoted.
key:/regexp/  - Match if key's value matches a regular expression.
key:(val1 OR val2 OR ...)
              - Short-hand for key:val1 OR key:val2. Values may be
                double-quoted strings or regexps.
*             - Match everything.

These terms can be combined into larger expressions as follows:

x y ...       - Match if x, y, etc. all match.
x AND y       - Same as x y.
x OR y        - Match if x or y match.
-x            - Match if x does not match.
(...)         - Subexpression.

Precise syntax:

expr     = andExpr {"OR" andExpr}
andExpr  = match {"AND"? match}
match    = "(" expr ")"
         | "-" match
         | "*"
         | key ":" value
         | key ":" "(" value {"OR" value} ")"
key      = word
value    = word
         | "/" regexp "/"

Projections

A projection expresses how to extract a tuple of data from a benchmark result, as well as a sort order for projected tuples.

A projection is a comma- or space-separated list of fields. Each field specifies a key and optionally a sort order and a filter as follows:

- "key" extracts the named field and orders it using the order values of this key are first observed in the data.

- "key@order" specifies one of the built-in named sort orders. This can be "alpha" or "num" for alphabetic or numeric sorting. "num" understands basic use of metric and IEC prefixes like "2k" and "1Mi".

- "key@(value value ...)" specifies a fixed value order for key. It also specifies a filter: if key has a value that isn't any of the specified values, the result is filtered out.

Precise syntax:

expr     = part {","? part}
part     = key
         | key "@" order
         | key "@" "(" word {word} ")"
key      = word
order    = word

Common syntax

Filters and projections share the following common base syntax:

word     = bareWord
         | double-quoted Go string
bareWord = [^-*"():@,][^ ():@,]*