973888 - mozStorage threads periodically write to disk during idle

Status: NEW

(Core :: General, defect)

Description

[Roberto Agostino Vitillo (:rvitillo)]

Many of the periodic disk writes on a complete idle system seems to be generated periodically from the mozStorage threads (measured with iotop with 6 tabs open pointing to cnn.com). Those writes account for about 25% of the total writes performed by FF in an one hour period (~60MB).

Comment 1

[Marco Bonardo [:mak]]

(In reply to Roberto Agostino Vitillo (:rvitillo) from comment #0)
> Many of the periodic disk writes on a complete idle system seems to be
> generated periodically from the mozStorage threads (measured with iotop with
> 6 tabs open pointing to cnn.com). Those writes account for about 25% of the
> total writes performed by FF in an one hour period (~60MB).

note that on idle we do maintenance work in various components, though those should only happen once in an idle cycle, not periodically. If some component is doing period writes continuously that should definitely be changed.
Also, there is bug 973591 that makes the system come back from idle unexpectedly due to content events.

Comment 2

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

Roberto, by any chance, do you know which files are hit?

Comment 3

[Roberto Agostino Vitillo (:rvitillo)]

About 90% of the times the file cookies.sqlite-wal is being written to.

Comment 4

[Marco Bonardo [:mak]]

I wonder if that is caused by the webpage actually storing cookies on idle... not many webpages care about stopping on idle and IIRC the cookies service doesn't do any special periodic work

Comment 5

[Henrik Skupin [:whimboo][⌚️UTC+1]]

Florian, have you ever seen that particular issue?

Comment 6

[Florian Quèze [:florian]]

(In reply to Henrik Skupin [:whimboo][⌚️UTC+1] from comment #5)

Florian, have you ever seen that particular issue?

No, but when I profile an idle Firefox I load about:blank, comment 0 says cnn.com was loaded. I wouldn't be surprised if the cnn page was self refreshing, and if we stored information related to that in the history database.