1618173 - TRR: We don't use DNS cache at all for the URL of DoH server

Status: RESOLVED FIXED

(Core :: Networking: DNS, defect, P1)

Description

[Kershaw Chang [:kershaw]]

In our current implementation, NS_HTTP_REFRESH_DNS [1] is set to the http channel that connects to the DoH server.
This causes the URL is resolved every time without using the DNS cache.

[1] https://searchfox.org/mozilla-central/rev/96f1457323cc598a36f5701f8e67aedaf97acfcf/netwerk/protocol/http/nsHttpChannel.cpp#6863

Comment 1

[Kershaw Chang [:kershaw]]

Attachment: Bug 1618173 - Don't set NS_HTTP_REFRESH_DNS for TRR service channel

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0df658fdc3ae
Don't set NS_HTTP_REFRESH_DNS for TRR service channel r=valentin

Comment 3

[Andrei Ciure[:aciure]]

https://hg.mozilla.org/mozilla-central/rev/0df658fdc3ae

Comment 4

[Valentin Gosu [:valentin] (he/him)]

[Tracking Requested - why for this release]:

This fixes a performance regression in Firefox 74.
Should be nominated for beta uplift.

Comment 5

[Kershaw Chang [:kershaw]]

Comment on attachment 9129154 [details]
Bug 1618173 - Don't set NS_HTTP_REFRESH_DNS for TRR service channel

Beta/Release Uplift Approval Request

• User impact if declined: Performance of DNS request is a bit dropped.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): The patch is quite simple and it only affects whether to read data from DNS cache.
• String changes made/needed: N/A

Comment 6

[Pascal Chevrel:pascalc]

Comment on attachment 9129154 [details]
Bug 1618173 - Don't set NS_HTTP_REFRESH_DNS for TRR service channel

Perf gain, low risk patch, uplift approved for 74 beta 9, thanks.

Comment 7

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/releases/mozilla-beta/rev/2fe1e017676b

Comment 8

[Marian Raiciof [:marauder]]

== Change summary for alert #25140 (as of Thu, 27 Feb 2020 08:52:38 GMT) ==

Improvements:

27% raptor-tp6m-instagram-geckoview-cold loadtime android-hw-p2-8-0-android-aarch64 pgo 2,070.04 -> 1,520.33
16% raptor-tp6m-bbc-geckoview-cold loadtime android-hw-g5-7-0-arm7-api-16 pgo 4,550.15 -> 3,800.50
14% raptor-tp6m-instagram-geckoview-cold android-hw-p2-8-0-android-aarch64 pgo 556.69 -> 477.65
11% raptor-tp6-microsoft-firefox-cold loadtime macosx1014-64-shippable opt 1,198.08 -> 1,071.08
10% raptor-tp6m-instagram-geckoview-cold loadtime android-hw-g5-7-0-arm7-api-16 pgo 3,328.58 -> 2,983.38
2% raptor-tp6-office-firefox-cold linux64-shippable-qr opt 462.94 -> 451.49
2% raptor-tp6-office-firefox-cold fcp linux64-shippable-qr opt 453.88 -> 442.92

For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=25140