1614639 - Most of the time spent in nsPermissionManager::InitDB before first paint is deleting expired permissions

Status: RESOLVED FIXED

(Core :: Permission Manager, task, P2)

Description

[Florian Quèze [:florian]]

Executing DELETE FROM moz_perms WHERE expireType = ?1 AND expireTime <= ?2 triggers 2 fsync syscalls on the main thread that are very slow compared to the other main thread I/O done by nsPermissionManager during early startup.

See this startup profile: https://perfht.ml/3bwQcr9

This is caused by the code at https://searchfox.org/mozilla-central/rev/a1592902acabf9bded973067133baaac1457f3d3/extensions/permissions/nsPermissionManager.cpp#2750-2770 that deletes expired permission entries before reading them all. I think we could instead ignore the expired entries while reading them, and later remove the expired entries from the database on disk during idle time, and preferably asynchronously.

Comment 1

[Mike Conley (:mconley) (:⚙️)]

This is a great find!

Comment 2

[Florian Quèze [:florian]]

I just saw another startup profile where these fsync calls don't exist, so it may be that we only need to write on the disk if there were actually some permission entries that expired.

Comment 3

[(no longer active)]

(In reply to Florian Quèze [:florian] from comment #0)

I think we could instead ignore the expired entries while reading them, and later remove the expired entries from the database on disk during idle time, and preferably asynchronously.

That should be quite feasible, I think.

(In reply to Florian Quèze [:florian] from comment #2)

I just saw another startup profile where these fsync calls don't exist, so it may be that we only need to write on the disk if there were actually some permission entries that expired.

That's certainly plausible...

Comment 4

[Mike Conley (:mconley) (:⚙️)]

Attachment: Bug 1614639 - Clear expired permissions from the database during idle off of the main thread. r?ehsan

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7ce25abc1155
Clear expired permissions from the database during idle off of the main thread. r=Ehsan

Comment 6

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/7ce25abc1155