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Side by Side Diff: tools/android/loading/prefetch_view.py

Issue 1813723002: clovis: Identify prefetchable resources from dependencies and tracing. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: . Created 4 years, 9 months ago
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1 # Copyright 2016 The Chromium 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 """Models the effect of prefetching resources from a loading trace.
6
7 For example, this can be used to evaluate NoState Prefetch
8 (https://goo.gl/B3nRUR).
9
10 When executed as a script, takes a trace as a command-line arguments and shows
11 how many requests were prefetched.
12 """
13
14 import itertools
15 import operator
16
17 import loading_trace
18 import request_dependencies_lens
19
20
21 class PrefetchSimulationView(object):
22 """Simulates the effect of prefetching resources discoverable by the preload
23 scanner.
24 """
25 def __init__(self, trace, dependencies_lens):
26 """Initializes an instance of PrefetchSimulationView.
27
28 Args:
29 trace: (LoadingTrace) a loading trace.
30 dependencies_lens: (RequestDependencyLens) request dependencies.
31 """
32 self.trace = trace
33 self.dependencies_lens = dependencies_lens
34 self._resource_events = self.trace.tracing_track.Filter(
35 categories=set([u'blink.net']))
36 assert len(self._resource_events.GetEvents()) > 0,\
37 'Was the "blink.net" category enabled at trace collection time?"'
38
39 def ParserDiscoverableRequests(self, request, recurse=False):
40 """Returns a list of requests discovered by the parser from a given request.
41
42 Args:
43 request: (Request) Root request.
44
45 Returns:
46 [Request]
47 """
48 # TODO(lizeb): handle the recursive case.
49 assert not recurse
50 discoverable_requests = [request]
51 first_request = self.dependencies_lens.GetRedirectChain(request)[-1]
52 deps = self.dependencies_lens.GetRequestDependencies()
53 for (first, second, reason) in deps:
54 if first.request_id == first_request.request_id and reason == 'parser':
55 discoverable_requests.append(second)
56 return discoverable_requests
57
58 def ExpandRedirectChains(self, requests):
59 return list(itertools.chain.from_iterable(
60 [self.dependencies_lens.GetRedirectChain(r) for r in requests]))
61
62 def PreloadedRequests(self, request):
63 """Returns the requests that have been preloaded from a given request.
64
65 This list is the set of request that are:
66 - Discoverable by the parser
67 - Found in the trace log.
68
69 Before looking for dependencies, this follows the redirect chain.
70
71 Args:
72 request: (Request) Root request.
73
74 Returns:
75 A list of Request. Does not include the root request. This list is a
76 subset of the one returned by ParserDiscoverableRequests().
77 """
78 # Preload step events are emitted in ResourceFetcher::preloadStarted().
79 preload_step_events = filter(
80 lambda e: e.args.get('step') == 'Preload',
81 self._resource_events.GetEvents())
82 preloaded_urls = set()
83 for preload_step_event in preload_step_events:
84 preload_event = self._resource_events.EventFromStep(preload_step_event)
85 if preload_event:
86 preloaded_urls.add(preload_event.args['url'])
87 parser_requests = self.ParserDiscoverableRequests(request)
88 preloaded_root_requests = filter(
89 lambda r: r.url in preloaded_urls, parser_requests)
90 # We can actually fetch the whole redirect chain.
91 return [request] + list(itertools.chain.from_iterable(
92 [self.dependencies_lens.GetRedirectChain(r)
93 for r in preloaded_root_requests]))
94
95
96 def _PrintSummary(prefetch_view):
97 requests = prefetch_view.trace.request_track.GetEvents()
98 first_request = prefetch_view.trace.request_track.GetEvents()[0]
99 parser_requests = prefetch_view.ExpandRedirectChains(
100 prefetch_view.ParserDiscoverableRequests(first_request))
101 preloaded_requests = prefetch_view.ExpandRedirectChains(
102 prefetch_view.PreloadedRequests(first_request))
103 print '%d requests, %d parser from the main request, %d preloaded' % (
104 len(requests), len(parser_requests), len(preloaded_requests))
105
106
107 def main(filename):
108 trace = loading_trace.LoadingTrace.FromJsonFile(filename)
109 dependencies_lens = request_dependencies_lens.RequestDependencyLens(trace)
110 prefetch_view = PrefetchSimulationView(trace, dependencies_lens)
111 _PrintSummary(prefetch_view)
112
113
114 if __name__ == '__main__':
115 import sys
116 main(sys.argv[1])
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