KDE Utils/kwallet/Benchmark

Summary

One of the main concerns users had with the wallet was that new entries weren't saved immediately (Bug #105752). Before actually getting to work and coding a workaround (appending new passwords to the file without reencrypting all of it or creating a second file where new passwords are appended) I benchmarked the existing encryption to check the actual overhead that would be incurred by saving to the kwl file as soon as passwords were entered.

Code

I used the following code for benchmarking. Please keep in mind:

• keys and passwords generated using random data are probably longer than the entries you actually have in your wallet.
• only syncing the wallet is benchmarked
• due to hd caching (and a rather modest filesize), most of the time reported should be used encrypting the data.

#include <kaboutdata.h>
#include <kcomponentdata.h>
#include <kcmdlineargs.h>
#include <kdebug.h>
#include <kwallet.h>
#include <QApplication>
#include <QTime>
#include <QFile>

#include "../backend/kwalletentry.h"
#include "../backend/kwalletbackend.h"

using namespace KWallet;

static int getRandomBlock(QByteArray& randBlock) {
  QFile devrand("/dev/urandom");
  if (devrand.open(QIODevice::ReadOnly)) {
    int rc = devrand.read(randBlock.data(), randBlock.size());
    if (rc != randBlock.size()) {
      return -3;              // not enough data read
    }
    return 0;
  }

  return -1;
}


int main(int argc, char **argv) {
  KAboutData aboutData("kwalletbench", 0, ki18n("kwalletbench"), "version");
  KComponentData componentData(&aboutData);
  QApplication app( argc, argv );

  Backend back("/tmp/benchmark.kwl", true);

  back.open("benchmark");
  back.createFolder("benchmark");
  back.setFolder("benchmark");

  for (int i = 0; i <= 100000; i+=100) {
    for (int j = 0; j < 100; ++j) {
      Entry entry;
      QByteArray key, value;
      key.resize(20);
      if (getRandomBlock(key) != 0) {
        kDebug(0) << "Error";
      }
      value.resize(50);
      if (getRandomBlock(value) != 0) {
        kDebug(0) << "Error";
      }
      entry.setType(Wallet::Password);
      entry.setKey(key);
      entry.setValue(value);
      back.writeEntry(&entry);
    }

    QTime _start = QTime::currentTime();
    back.sync("benchmark");
    QTime _end = QTime::currentTime();

    kDebug(0) << i << ";" << _start.msecsTo(_end);
  }

  back.close();

  return 0;
}

Results

I benchmarked on a Q6600. As the encrypting code is single-threaded, only one core (2.4GHz) is being used. Please bear in mind that I didn't bother to run the test several times as the results are pretty clear - unfortunately this makes some of the numbers seem a little weird.

• DebugFull
  • 1 password: 16ms
  • 100 passwords: 15ms
  • 1000 passwords: 32ms
  • 5000 passwords: 107ms
  • 10000 passwords: 192ms
• Release
  • 1 password: 8ms
  • 100 passwords: 5ms
  • 1000 passwords: 15ms
  • 5000 passwords: 25ms
  • 10000 passwords: 56ms

Discussion

I assume that your usual wallet will contain less than 1000 entries. Due to the fact that any workaround would have to encrypt at least 1 entry (~ 8ms) this workaround would save around 15ms - 8ms = 7ms. This is clearly insignificant. Big overhead for syncing the wallet seems to be a myth.