729165 - Make cache mode SSD-friendly: avoid small writes

Status: NEW

(Core :: Networking: Cache, defect, P5)

Description

[Boris Zbarsky [:bzbarsky]]

See data in bug 727409 comment 0.

Comment 1

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

See also bug 727409 comment 9.

bug 727409 comment 0 measures the number of application-level writes to files. There is, of course, not a one-to-one correspondence between application-level writes and actual writes to the disk, because operating systems buffer writes. Plus, we never fsync() in the cache, so we leave the OS with plenty of freedom to optimize our writes.

BUT, other parts of Firefox DO fsync their files pretty regularly, and on some filesystems (ext3 on Linux, in particular), those fsyncs have the horrible effect of syncing *all* buffered writes, not just the writes buffered for the file being fsync'd.

See also bug 446876, and especially bug 446876, which discusses a mechanism for buffering writes in memory for a different reason, but which would probably help with any problem that may or not exist here.

Comment 2

[Phoenix]

(In reply to Brian Smith (:bsmith) from comment #1)
> See also bug 446876, and especially bug 446876
You give same bug number twice :)

Comment 3

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

...especially bug 446876 comment 15.

Comment 4

[Firefox Bug Husbandry Bot]

Bulk change to priority: https://bugzilla.mozilla.org/show_bug.cgi?id=1399258