1# Copyright (c) 2012 The Chromium OS Authors. All rights reserved. 2# Use of this source code is governed by a BSD-style license that can be 3# found in the LICENSE file. 4 5"""A tool to measure single-stream link bandwidth using HTTP connections.""" 6 7import logging, random, time, urllib2 8 9import numpy.random 10 11TIMEOUT = 90 12 13 14class Error(Exception): 15 pass 16 17 18def TimeTransfer(url, data): 19 """Transfers data to/from url. Returns (time, url contents).""" 20 start_time = time.time() 21 result = urllib2.urlopen(url, data=data, timeout=TIMEOUT) 22 got = result.read() 23 transfer_time = time.time() - start_time 24 if transfer_time <= 0: 25 raise Error("Transfer of %s bytes took nonsensical time %s" 26 % (url, transfer_time)) 27 return (transfer_time, got) 28 29 30def TimeTransferDown(url_pattern, size): 31 url = url_pattern % {'size': size} 32 (transfer_time, got) = TimeTransfer(url, data=None) 33 if len(got) != size: 34 raise Error('Got %d bytes, expected %d' % (len(got), size)) 35 return transfer_time 36 37 38def TimeTransferUp(url, size): 39 """If size > 0, POST size bytes to URL, else GET url. Return time taken.""" 40 data = numpy.random.bytes(size) 41 (transfer_time, _) = TimeTransfer(url, data) 42 return transfer_time 43 44 45def BenchmarkOneDirection(latency, label, url, benchmark_function): 46 """Transfer a reasonable amount of data and record the speed. 47 48 Args: 49 latency: Time for a 1-byte transfer 50 label: Label to add to perf keyvals 51 url: URL (or pattern) to transfer at 52 benchmark_function: Function to perform actual transfer 53 Returns: 54 Key-value dictionary, suitable for reporting to write_perf_keyval. 55 """ 56 57 size = 1 << 15 # Start with a small download 58 maximum_size = 1 << 24 # Go large, if necessary 59 multiple = 1 60 61 remaining = 2 62 transfer_time = 0 63 64 # Long enough that startup latency shouldn't dominate. 65 target = max(20 * latency, 10) 66 logging.info('Target time: %s' % target) 67 68 while remaining > 0: 69 size = min(int(size * multiple), maximum_size) 70 transfer_time = benchmark_function(url, size) 71 logging.info('Transfer of %s took %s (%s b/s)' 72 % (size, transfer_time, 8 * size / transfer_time)) 73 if transfer_time >= target: 74 break 75 remaining -= 1 76 77 # Take the latency into account when guessing a size for a 78 # larger transfer. This is a pretty simple model, but it 79 # appears to work. 80 adjusted_transfer_time = max(transfer_time - latency, 0.01) 81 multiple = target / adjusted_transfer_time 82 83 if remaining == 0: 84 logging.warning( 85 'Max size transfer still took less than minimum desired time %s' 86 % target) 87 88 return {'seconds_%s_fetch_time' % label: transfer_time, 89 'bytes_%s_bytes_transferred' % label: size, 90 'bits_second_%s_speed' % label: 8 * size / transfer_time, 91 } 92 93 94def HttpSpeed(download_url_format_string, 95 upload_url): 96 """Measures upload and download performance to the supplied URLs. 97 98 Args: 99 download_url_format_string: URL pattern with %(size) for payload bytes 100 upload_url: URL that accepts large POSTs 101 Returns: 102 A dict of perf_keyval 103 """ 104 # We want the download to be substantially longer than the 105 # one-byte fetch time that we can isolate bandwidth instead of 106 # latency. 107 latency = TimeTransferDown(download_url_format_string, 1) 108 109 logging.info('Latency is %s' % latency) 110 111 down = BenchmarkOneDirection( 112 latency, 113 'downlink', 114 download_url_format_string, 115 TimeTransferDown) 116 117 up = BenchmarkOneDirection( 118 latency, 119 'uplink', 120 upload_url, 121 TimeTransferUp) 122 123 up.update(down) 124 return up 125