1777673 - [meta] Investigate performance impact of the shim redirect

Status: RESOLVED FIXED

(Core :: XPConnect, task)

Description

[Tooru Fujisawa [:arai]]

The shim introduced by bug 1766761 triggers extra load for chrome:// and resource:// URIs, and it might cause some performance regression.

We should investigate if there's any notable regression,
and also in that case, see if adding fast-path with static redirect list there makes any difference.

Comment 1

[Tooru Fujisawa [:arai]]

Very straightforward fast-path
https://hg.mozilla.org/try/rev/8e7bcdc43c787f60ca35c7d810fe334ac0e45a99

Given there will be ~1300 items, we'd better having perfect hash or something ultimately. now testing that approach as well.

Comment 2

[Tooru Fujisawa [:arai]]

Testing the performance with bug 1777486 patch (Services.jsm and XPCOMUtils.jsm migrated without touching the consumers)

Redirect after failure: https://treeherder.mozilla.org/perfherder/compare?originalProject=try&originalRevision=d53d346387633abf09450f0212d7c41b1bea3f25&newProject=try&newRevision=cd4cb9a330e83d5f008175e578bfbfaa286f1c76&framework=1&page=1
Redirect with static list: https://treeherder.mozilla.org/perfherder/compare?originalProject=try&originalRevision=d53d346387633abf09450f0212d7c41b1bea3f25&newProject=try&newRevision=ec2f0bedb57c08c1b9346955796f71f3b185fd4c&framework=1&page=1&showOnlyComparable=1

Comment 3

[Tooru Fujisawa [:arai]]

The current code doesn't cache the redirect itself, so the not-found error will happen every time.
I'll check the performance with caching the redirect as well.

Comment 4

[Tooru Fujisawa [:arai]]

the comparison above clearly shows that the current shim hits regression, up to 10% in startup performance.

Comment 5

[Tooru Fujisawa [:arai]]

Redirect after failure + cache redirect: https://treeherder.mozilla.org/perfherder/compare?originalProject=try&originalRevision=d53d346387633abf09450f0212d7c41b1bea3f25&newProject=try&newRevision=4289e2c0f46ad7c57514b5b650c2dcad3d283cb9&framework=1

Looks like the perf regression can be solved by caching the redirect.