Significant slowdown for each file written

[natevw]

var vol = require("./img_volume.js").createDriverSync("/Users/natevw/Desktop/fat32.img"),
    fs = require("./").createFileSystem(vol, {umask:0020, uid:99, gid:42});

function writeData(data) {
  setImmediate(function () {
    var t1 = Date.now();
    fs.writeFile("sample-"+t1+".bin", data, function (e) {
      var t2 = Date.now();
      console.log(t2 - t1);
      writeData(data);
    });
  });
}
writeData(Buffer(512*1024));

The output grows steadily, starting at around 330ms for the write and growing to 2004ms after less than 50 files: https://gist.github.com/natevw/41ac4cf4f3788d4193ed

Contrary to https://github.com/tessel/sdcard/issues/20, creating a new filesystem instance (or in this case: a whole new process!) does not keep the timings low.

[natevw]

Script updated for on-device testing too:

var fs = null,
    data = Buffer(512*1024);

if (0) {
  var vol = require("./img_volume.js").createDriverSync("/Users/natevw/Desktop/fat32.img"),
      fs = require("./").createFileSystem(vol, {umask:0020, uid:99, gid:42});
  writeData();
} else {
  var sd = require('sdcard').use(require('tessel').port['A'], {getFilesystems:true}),
      fs = null;
  sd.on('ready', function(e, fss) {
    if (e) throw e;
    fs = fss[0];
    writeData();
  });
}

function writeData() {
  setImmediate(function () {
    var t1 = Date.now();
    fs.writeFile("sample-"+t1+".bin", data, function (e) {
      var t2 = Date.now();
      console.log(t2 - t1);
      writeData();
    });
  });
}

[natevw]

Couple notes:

• sdcard is currently dependent on fatfs@^0.9.5 which predates a bunch of caching fixes/improvements!
• with latest version, I see a slowdown as the number of files grows, and then a bit of a speedup back to a stable point: https://gist.github.com/natevw/7e5880db3a8e86b42639 (the original script above exhibits similar: https://gist.github.com/natevw/d35155eeccf53c6ff5ab)

[natevw]

Latest test script:

var fs = null,
    data = Buffer(60*1024);

if (0) {
  var vol = require("fatfs/img_volume.js").createDriverSync("/Users/natevw/Desktop/fat32.img"),
      fs = require('fatfs').createFileSystem(vol, {umask:0020, uid:99, gid:42});
  writeData();
} else {
  var sd = require("./").use(require('tessel').port['A'], {getFilesystems:true}),
      fs = null;
  sd.on('ready', function (fss) {
    fs = fss[0];
    writeData();
  });
}

function writeData() {
  setImmediate(function () {
    var t1 = Date.now();
    //process.stdout.write("--> Writing "+t1+"…\t");
    fs.writeFile("sample-"+t1+".bin", data, function (e) {
      var t2 = Date.now();
      console.log(t2 - t1);
      writeData();
    });
  });
}

…gives results like this on a dirty card (i.e. already lots of existing files):

25544
22281
21707
22458
22115
23038
22843
22223

So at this point there's still AFAIK a weird temporary slowdown during the first couple dozen files, but it does seem to stabilize.