commit only journal entries older than commit period?

["Leon Woestenberg" <leon.woestenberg@gmail.com>]

Hello all,

this is something I have long wondered about but have been afraid to ask.

When my system is chewing away on builds, the disk I/O write access
pattern of my ext3 root filesystem (using CFQ, Intel SATA controller,
hard disk) when visualized by GNOME System Monitor clearly shows a
repetitive landscape of large peaks, 5 seconds apart, which not much
activity inbetween.

I understand that's due to the ex3 journal commit interval (defaults
to 5 seconds).

But why isn't the filesystem continuously committing only that part of
the journal that is older than 5 seconds?

I would then expect the write requests to be smoothened over time,
which can only be good in terms of performance and low latency.

Regards,
-- 
Leon