875971 - Main thread SQLite: PRAGMA cache_size = -2048

Status: RESOLVED DUPLICATE of bug 885732

(Toolkit :: Storage, defect)

Description

[(dormant account)]

please don't execute sql queries synchronously.

Comment 1

[(dormant account)]

This creeped up into top ~20 slow main thread sql usages according to telemetry.

Comment 2

[Gregory Szorc [:gps]]

FHR uses Sqlite.jsm which executes *everything* (except connection open and close because there are no off-main-thread APIs for that) off the main thread. There is no statement execution API in Sqlite.jsm that is supposed to execute on the main thread.

This is either misidentification of main thread I/O or Sqlite.jsm/Storage is misbehaving. Either way, not a FHR bug.

https://hg.mozilla.org/mozilla-central/file/7a2f7a45819a/services/metrics/storage.jsm#l1115
https://hg.mozilla.org/mozilla-central/file/7a2f7a45819a/toolkit/modules/Sqlite.jsm#l454
https://hg.mozilla.org/mozilla-central/file/7a2f7a45819a/toolkit/modules/Sqlite.jsm#l767

I'm on holiday. Someone else will have to dig into this.

Comment 3

[(dormant account)]

Looks like it's due to main thread io in open() :(

http://dxr.mozilla.org/mozilla-central/storage/src/mozStorageConnection.cpp#l581

David/mak, when are we getting a proper async open?

Comment 4

[David Teller [:Yoric] - still alive but not very active]

Yeah, it's in open().
Async open is waiting for review (see bug 702559).

Comment 6

[Marco Bonardo [:mak]]

fwiw, the only thing we can do here is convert consumers from sync to async, it's pretty clear we can't avoid main-thread queries for a synchronous consumer.