Subject: Re: [RFC IPROUTE 00/05]: Time cleanups

From: Patrick McHardy <[email-masked]>
Date: Fri, 23 Jun 2006 20:09:18 +0200

D'oh, got Stephen's address wrong. Please fix it (add 's' in front) in
replies to this thread.

Patrick McHardy wrote:
> I'm currently adding support for ktime as clocksource to the qdisc layer and
> in the course of doing that cleaned up the iproute time handling a bit to
> make it easier to use a different internal clock resultion and audit for
> integer overflows.
> 
> Increasing iproutes internal clock resolution is necessary for all token bucket
> based schedulers to take advantage of a higher kernel clock resolution because
> the kernel only does lookups and additions/subtractions, which can never result
> in values that have a higher precision that those passed from userspace.
> 
> The way I imagine it we have to keep the old clock sources around for userspace
> compatibility since they can't deal with the higher precision values. iproute is
> changed to use nsec internally and reads the kernel clock resulution from
> /proc/net/psched (third value, currently assumed to always be 10^6) to convert
> it's internal resolution to that of the kernel. With ktime as clocksource the
> kernel will report a resulution of 10^9. The downside is that distributors can't
> enable ktime unless they want to break compatibility with old iproute versions.
> Any better suggestions are welcome of course.
> 
> 
>  tc/m_estimator.c  |    4 ++--
>  tc/m_police.c     |    2 +-
>  tc/q_cbq.c        |   15 ++++++++-------
>  tc/q_hfsc.c       |   18 +++++++++---------
>  tc/q_htb.c        |    4 ++--
>  tc/q_netem.c      |   12 +++---------
>  tc/q_tbf.c        |   20 ++++++++++----------
>  tc/tc_cbq.c       |    8 ++++----
>  tc/tc_core.c      |   31 +++++++++++++++++++++++--------
>  tc/tc_core.h      |    9 +++++++--
>  tc/tc_estimator.c |    2 +-
>  tc/tc_red.c       |    2 +-
>  tc/tc_util.c      |   33 +++++++++++++++++++--------------
>  tc/tc_util.h      |    7 ++++---
>  14 files changed, 94 insertions(+), 73 deletions(-)
> 
> Patrick McHardy:
>       [IPROUTE]: Use tc_calc_xmittime where appropriate
>       [IPROUTE]: Introduce tc_calc_xmitsize and use where appropriate
>       [IPROUTE]: Introduce TIME_UNITS_PER_SEC to represent internal clock resulution
>       [IPROUTE]: Replace "usec" by "time" in function names
>       [IPROUTE]: Add sprint_ticks() function and use in CBQ