diff options
Diffstat (limited to 'chrome/browser/net/dns_global.cc')
| -rw-r--r-- | chrome/browser/net/dns_global.cc | 32 |
1 files changed, 29 insertions, 3 deletions
diff --git a/chrome/browser/net/dns_global.cc b/chrome/browser/net/dns_global.cc index a61b85d..f7fe990 100644 --- a/chrome/browser/net/dns_global.cc +++ b/chrome/browser/net/dns_global.cc @@ -543,13 +543,21 @@ DnsGlobalInit::DnsGlobalInit(PrefService* user_prefs, // latency of page loads. FieldTrial::Probability kDivisor = 100; // For each option (i.e., non-default), we have a fixed probability. - FieldTrial::Probability kProbabilityPerGroup = 3; // 3% probability. + FieldTrial::Probability kProbabilityPerGroup = 5; // 5% probability. trial_ = new FieldTrial("DnsImpact", kDivisor); // First option is to disable prefetching completely. int disabled_prefetch = trial_->AppendGroup("_disabled_prefetch", kProbabilityPerGroup); + + + // We're running two experiments at the same time. The first set of trials + // modulates the delay-time until we declare a congestion event (and purge + // our queue). The second modulates the number of concurrent resolutions + // we do at any time. Users are in exactly one trial (or the default) during + // any one run, and hence only one experiment at a time. + // Experiment 1: // Set congestion detection at 250, 500, or 750ms, rather than the 1 second // default. int max_250ms_prefetch = trial_->AppendGroup("_max_250ms_queue_prefetch", @@ -561,6 +569,16 @@ DnsGlobalInit::DnsGlobalInit(PrefService* user_prefs, // Set congestion detection at 2 seconds instead of the 1 second default. int max_2s_prefetch = trial_->AppendGroup("_max_2s_queue_prefetch", kProbabilityPerGroup); + // Experiment 2: + // Set max simultaneous resoultions to 2, 4, or 6, and scale the congestion + // limit proportionally (so we don't impact average probability of asserting + // congesion very much). + int max_2_concurrent_prefetch = trial_->AppendGroup( + "_max_2 concurrent_prefetch", kProbabilityPerGroup); + int max_4_concurrent_prefetch = trial_->AppendGroup( + "_max_4 concurrent_prefetch", kProbabilityPerGroup); + int max_6_concurrent_prefetch = trial_->AppendGroup( + "_max_6 concurrent_prefetch", kProbabilityPerGroup); trial_->AppendGroup("_default_enabled_prefetch", FieldTrial::kAllRemainingProbability); @@ -571,9 +589,7 @@ DnsGlobalInit::DnsGlobalInit(PrefService* user_prefs, if (trial_->group() != disabled_prefetch) { // Initialize the DNS prefetch system. - size_t max_concurrent = kMaxPrefetchConcurrentLookups; - int max_queueing_delay_ms = kMaxPrefetchQueueingDelayMs; if (trial_->group() == max_250ms_prefetch) @@ -584,6 +600,16 @@ DnsGlobalInit::DnsGlobalInit(PrefService* user_prefs, max_queueing_delay_ms = 750; else if (trial_->group() == max_2s_prefetch) max_queueing_delay_ms = 2000; + if (trial_->group() == max_2_concurrent_prefetch) + max_concurrent = 2; + else if (trial_->group() == max_4_concurrent_prefetch) + max_concurrent = 4; + else if (trial_->group() == max_6_concurrent_prefetch) + max_concurrent = 6; + // Scale acceptable delay so we don't cause congestion limits to fire as + // we modulate max_concurrent (*if* we are modulating it at all). + max_queueing_delay_ms = (kMaxPrefetchQueueingDelayMs * + kMaxPrefetchConcurrentLookups) / max_concurrent; TimeDelta max_queueing_delay( TimeDelta::FromMilliseconds(max_queueing_delay_ms)); |