#!/usr/bin/env python3
  #
  # Copyright (C) 2019 Tejun Heo <tj@kernel.org>
  # Copyright (C) 2019 Andy Newell <newella@fb.com>
  # Copyright (C) 2019 Facebook
  
  desc = """
  Generate linear IO cost model coefficients used by the blk-iocost
  controller.  If the target raw testdev is specified, destructive tests
  are performed against the whole device; otherwise, on
  ./iocost-coef-fio.testfile.  The result can be written directly to
  /sys/fs/cgroup/io.cost.model.
  
  On high performance devices, --numjobs > 1 is needed to achieve
  saturation.
  
  See Documentation/admin-guide/cgroup-v2.rst and block/blk-iocost.c
  for more details.
  """
  
  import argparse
  import re
  import json
  import glob
  import os
  import sys
  import atexit
  import shutil
  import tempfile
  import subprocess
  
  parser = argparse.ArgumentParser(description=desc,
                                   formatter_class=argparse.RawTextHelpFormatter)
  parser.add_argument('--testdev', metavar='DEV',
                      help='Raw block device to use for testing, ignores --testfile-size')
  parser.add_argument('--testfile-size-gb', type=float, metavar='GIGABYTES', default=16,
                      help='Testfile size in gigabytes (default: %(default)s)')
  parser.add_argument('--duration', type=int, metavar='SECONDS', default=120,
                      help='Individual test run duration in seconds (default: %(default)s)')
  parser.add_argument('--seqio-block-mb', metavar='MEGABYTES', type=int, default=128,
                      help='Sequential test block size in megabytes (default: %(default)s)')
  parser.add_argument('--seq-depth', type=int, metavar='DEPTH', default=64,
                      help='Sequential test queue depth (default: %(default)s)')
  parser.add_argument('--rand-depth', type=int, metavar='DEPTH', default=64,
                      help='Random test queue depth (default: %(default)s)')
  parser.add_argument('--numjobs', type=int, metavar='JOBS', default=1,
                      help='Number of parallel fio jobs to run (default: %(default)s)')
  parser.add_argument('--quiet', action='store_true')
  parser.add_argument('--verbose', action='store_true')
  
  def info(msg):
      if not args.quiet:
          print(msg)
  
  def dbg(msg):
      if args.verbose and not args.quiet:
          print(msg)
  
  # determine ('DEVNAME', 'MAJ:MIN') for @path
  def dir_to_dev(path):
      # find the block device the current directory is on
      devname = subprocess.run(f'findmnt -nvo SOURCE -T{path}',
                               stdout=subprocess.PIPE, shell=True).stdout
      devname = os.path.basename(devname).decode('utf-8').strip()
  
      # partition -> whole device
      parents = glob.glob('/sys/block/*/' + devname)
      if len(parents):
          devname = os.path.basename(os.path.dirname(parents[0]))
      rdev = os.stat(f'/dev/{devname}').st_rdev
      return (devname, f'{os.major(rdev)}:{os.minor(rdev)}')
  
  def create_testfile(path, size):
      global args
  
      if os.path.isfile(path) and os.stat(path).st_size == size:
          return
  
      info(f'Creating testfile {path}')
      subprocess.check_call(f'rm -f {path}', shell=True)
      subprocess.check_call(f'touch {path}', shell=True)
      subprocess.call(f'chattr +C {path}', shell=True)
      subprocess.check_call(
          f'pv -s {size} -pr /dev/urandom {"-q" if args.quiet else ""} | '
          f'dd of={path} count={size} '
          f'iflag=count_bytes,fullblock oflag=direct bs=16M status=none',
          shell=True)
  
  def run_fio(testfile, duration, iotype, iodepth, blocksize, jobs):
      global args
  
      eta = 'never' if args.quiet else 'always'
      outfile = tempfile.NamedTemporaryFile()
      cmd = (f'fio --direct=1 --ioengine=libaio --name=coef '
             f'--filename={testfile} --runtime={round(duration)} '
             f'--readwrite={iotype} --iodepth={iodepth} --blocksize={blocksize} '
             f'--eta={eta} --output-format json --output={outfile.name} '
             f'--time_based --numjobs={jobs}')
      if args.verbose:
          dbg(f'Running {cmd}')
      subprocess.check_call(cmd, shell=True)
      with open(outfile.name, 'r') as f:
          d = json.loads(f.read())
      return sum(j['read']['bw_bytes'] + j['write']['bw_bytes'] for j in d['jobs'])
  
  def restore_elevator_nomerges():
      global elevator_path, nomerges_path, elevator, nomerges
  
      info(f'Restoring elevator to {elevator} and nomerges to {nomerges}')
      with open(elevator_path, 'w') as f:
          f.write(elevator)
      with open(nomerges_path, 'w') as f:
          f.write(nomerges)
  
  
  args = parser.parse_args()
  
  missing = False
  for cmd in [ 'findmnt', 'pv', 'dd', 'fio' ]:
      if not shutil.which(cmd):
          print(f'Required command "{cmd}" is missing', file=sys.stderr)
          missing = True
  if missing:
      sys.exit(1)
  
  if args.testdev:
      devname = os.path.basename(args.testdev)
      rdev = os.stat(f'/dev/{devname}').st_rdev
      devno = f'{os.major(rdev)}:{os.minor(rdev)}'
      testfile = f'/dev/{devname}'
      info(f'Test target: {devname}({devno})')
  else:
      devname, devno = dir_to_dev('.')
      testfile = 'iocost-coef-fio.testfile'
      testfile_size = int(args.testfile_size_gb * 2 ** 30)
      create_testfile(testfile, testfile_size)
      info(f'Test target: {testfile} on {devname}({devno})')
  
  elevator_path = f'/sys/block/{devname}/queue/scheduler'
  nomerges_path = f'/sys/block/{devname}/queue/nomerges'
  
  with open(elevator_path, 'r') as f:
      elevator = re.sub(r'.*\[(.*)\].*', r'\1', f.read().strip())
  with open(nomerges_path, 'r') as f:
      nomerges = f.read().strip()
  
  info(f'Temporarily disabling elevator and merges')
  atexit.register(restore_elevator_nomerges)
  with open(elevator_path, 'w') as f:
      f.write('none')
  with open(nomerges_path, 'w') as f:
      f.write('1')
  
  info('Determining rbps...')
  rbps = run_fio(testfile, args.duration, 'read',
                 1, args.seqio_block_mb * (2 ** 20), args.numjobs)
  info(f'
  rbps={rbps}, determining rseqiops...')
  rseqiops = round(run_fio(testfile, args.duration, 'read',
                           args.seq_depth, 4096, args.numjobs) / 4096)
  info(f'
  rseqiops={rseqiops}, determining rrandiops...')
  rrandiops = round(run_fio(testfile, args.duration, 'randread',
                            args.rand_depth, 4096, args.numjobs) / 4096)
  info(f'
  rrandiops={rrandiops}, determining wbps...')
  wbps = run_fio(testfile, args.duration, 'write',
                 1, args.seqio_block_mb * (2 ** 20), args.numjobs)
  info(f'
  wbps={wbps}, determining wseqiops...')
  wseqiops = round(run_fio(testfile, args.duration, 'write',
                           args.seq_depth, 4096, args.numjobs) / 4096)
  info(f'
  wseqiops={wseqiops}, determining wrandiops...')
  wrandiops = round(run_fio(testfile, args.duration, 'randwrite',
                            args.rand_depth, 4096, args.numjobs) / 4096)
  info(f'
  wrandiops={wrandiops}')
  restore_elevator_nomerges()
  atexit.unregister(restore_elevator_nomerges)
  info('')
  
  print(f'{devno} rbps={rbps} rseqiops={rseqiops} rrandiops={rrandiops} '
        f'wbps={wbps} wseqiops={wseqiops} wrandiops={wrandiops}')