dcat  

dcat is a very simple tool for examining performance of I/O facilities available in the D programming language ecosystem. dcat reads input from a file or standard input and writes results to standard output. The I/O methods to test are specified on the command line. Most tests focus on reading and writing line-by-line. Use Unix time or similar to get timing data.

Clone this repo and build with LDC using the command:

$ dub build --compiler=ldc2 --build=release-lto-pgo --build-mode=allAtOnce --combined

The above builds with LTO and PGO. To skip PGO and use LTO only:

$ dub build --compiler=ldc2 --build=release-lto --build-mode=allAtOnce --combined

The executable is written to ./bin/dcat. Run dcat --help to see a list of tests available, or simply look at the code.

Build Notes:

• The dub.json file works with dub-1.15.0 and later but not dub-1.14.0 and earlier. To use with dub-1.14.0 changing $$? to $? in the dub.json file, in the cli-test section. See dub issue #1709.
• dub packaged with dmd-2.089.x and earlier has intermittent failures on travis-ci due to stack overflows. See: druntime PR #2904. These issues are addressed in dmd-2.090.0 and ldc-1.20.0.
• This project does not build with dmd-2.088.0. This is due to an issue in the io package version 0.2.2 library triggered by regression in DMD. See druntime PR #2853. Other compiler versions are fine.

Tests available are based on components from:

• D Standard Library
• Steven Schveighoffer's iopipe library
• Martin Nowak's std.io library
• eBay's TSV Utilities

Some benchmarks generated with this tool can be found on the issues page.

Example timing run

The example below performs runs on the google one-gram file for the letter 's', available from the Google Books ngram datasets. It has been downloaded as googlebooks-eng-all-1gram-20120701-s.tsv. The command below was run on MacOS and uses the GNU versions of time and wc, which are installed as gtime and gwc by Homebrew.

This command runs several of the available dcat tests five time each and writes the results to the file perf-results.tsv. The [g]wc` command is used to load the file into disk cache so every run starts from the same basis with respect to caches.

$ echo $'test\telapsed\tuser\tsystem\tcpu_pct\tmem' > perf-results.tsv; \
  gwc -l googlebooks-eng-all-1gram-20120701-s.tsv; \
  for i in 1 2 3 4 5; \
      do echo "---> Run ${i}"; \
      for t in byLineInRawOut byLineInBufOut bufferedByLineInBufOut iopipeByLineInRawOut iopipeByLineInBufOut; \
          do gtime -p --format="${t}\t%e\t%U\t%S\t%P\t%M" -a -o perf-results.tsv \
              ./bin/dcat -t ${t}  googlebooks-eng-all-1gram-20120701-s.tsv  > /dev/null; \
      done; \
  done

The results are written to perf-results.tsv.

$ head perf-results.tsv
test	elapsed	user	system	cpu_pct	mem
byLineInRawOut	22.50	21.63	0.84	99%	1832
byLineInBufOut	9.32	8.46	0.85	99%	1816
bufferedByLineInBufOut	6.41	5.98	0.42	99%	1976
iopipeByLineInRawOut	19.74	19.26	0.47	99%	1816
iopipeByLineInBufOut	2.95	2.48	0.46	99%	1836
byLineInRawOut	22.39	21.53	0.84	99%	1800
byLineInBufOut	9.31	8.45	0.85	99%	1828
bufferedByLineInBufOut	6.41	5.98	0.42	99%	1976
iopipeByLineInRawOut	19.86	19.35	0.48	99%	1816

Median timing values can be calculated using tsv-utils as follows:

$ tsv-summarize -H --group-by 1 --median 2-4,6 perf-results.tsv | tsv-pretty -p 2
test                    elapsed_median  user_median  system_median  mem_median
byLineInRawOut                   22.41        21.56           0.84        1812
byLineInBufOut                    9.32         8.45           0.85        1816
bufferedByLineInBufOut            6.41         5.98           0.42        1976
iopipeByLineInRawOut             19.75        19.26           0.47        1828
iopipeByLineInBufOut              2.96         2.49           0.46        1836