Performance for loading a blob at a particular commit and accessing some of its immutable fields. Benchmark A access its fields and crosses the runtime boundary for each field access. Benchmark B does not access any fields and thus doesn't cross the runtime boundary as often (to be precise, 7 times versus 4 times). As you can see, performance is…

Benchmark A

var git = require('../'),
    path = require('path');

// This example opens a certain file, `README.md`, at a particular commit,
// and prints the first 10 lines as well as some metadata.

function doIt(cb) {
  git.Repo.open(path.resolve(__dirname, '../.git'), function(error, repo) {
    if (error) throw error;

    repo.getCommit('59b20b8d5c6ff8d09518454d4dd8b7b30f095ab5', function(error, commit) {
      if (error) throw error;

      commit.getEntry('README.md', function(error, entry) {
        if (error) throw error;

        entry.getBlob(function(error, blob) {
          if (error) throw error;

          cb([entry.name(), entry.sha(), blob.size()]); // crosses the runtime barrier 3 times.
        });
      });
    });
  });
}

function repeat(i, f, next) {
  if (i == 0) return next();

  f(function() { repeat(i - 1, f, next) })
}

var warmup = 100,
    num = 2000;

repeat(warmup, doIt, function() {
  var start = new Date().getTime();
  repeat(num, doIt, function() {
    var end = new Date().getTime();
    console.log('Completed ' + num + ' operations, at ' + ((end - start) / num).toString() + 'ms per operation');
  })
});

// Completed 2000 operations, at 0.64ms per operation
// Completed 2000 operations, at 0.6435ms per operation
// Completed 2000 operations, at 0.638ms per operation
// Completed 2000 operations, at 0.6505ms per operation

Benchmark B

var git = require('../'),
    path = require('path');

// This example opens a certain file, `README.md`, at a particular commit,
// and prints the first 10 lines as well as some metadata.

function doIt(cb) {
  git.Repo.open(path.resolve(__dirname, '../.git'), function(error, repo) {
    if (error) throw error;

    repo.getCommit('59b20b8d5c6ff8d09518454d4dd8b7b30f095ab5', function(error, commit) {
      if (error) throw error;

      commit.getEntry('README.md', function(error, entry) {
        if (error) throw error;

        entry.getBlob(function(error, blob) {
          if (error) throw error;

          cb() //[entry.name(), entry.sha(), blob.size()]); // crosses the runtime barrier 3 times.
        });
      });
    });
  });
}

function repeat(i, f, next) {
  if (i == 0) return next();

  f(function() { repeat(i - 1, f, next) })
}

var warmup = 100,
    num = 2000;

repeat(warmup, doIt, function() {
  var start = new Date().getTime();
  repeat(num, doIt, function() {
    var end = new Date().getTime();
    console.log('Completed ' + num + ' operations, at ' + ((end - start) / num).toString() + 'ms per operation');
  })
});

// Completed 2000 operations, at 0.639ms per operation
// Completed 2000 operations, at 0.6315ms per operation
// Completed 2000 operations, at 0.63ms per operation