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RE: Changing system timer resolution
- From: "Jurica Baricevic" <jura at INTESIS dot hr>
- To: <ecos-discuss at sources dot redhat dot com>
- Cc: "Grant Edwards" <grante at visi dot com>
- Date: Wed, 28 Nov 2001 18:19:05 +0100
- Subject: RE: [ECOS] Changing system timer resolution
Grant Edwards wrote (Wednesday, November 28, 2001 17:28):
> I've gotten repeated requests from customers for different
> (generally smaller) system timer resolutions. Changing the
> timer resolution is easy enough, but doing so breaks things
> things since a lot of application level code (system tests, TCP
> stack, DHCP task, etc.) depends on the assumption that a system
> timer tick is 10ms. [This assumption seems like a fairly
> fundamental flaw for RTOS application code.]
>
> It would be awfully nice if there were a simple way for an
> application to determine the system timer tick resolution (e.g.
> macros/functions to convert back and forth between
> seconds<->ticks and ms<->ticks). I know this information is
> available, but it's buried pretty deeply and is difficult to
> use.
>
I absolutely agree with the statement above. Currently, I am using some
"home-made" calculations and macros in my applications (i.e. for
cyg_thread_delay()) and they look quite awkward. Some 'easy to use'
conversion between real time and system tick in any form (API, macro) would
be quite useful.
Digression:
Also, it would be nice to have some high-resolution performance counter for
more precise time handling. For example, microsecond handling is quite
common in today's RTOS applications. The high-resolution counter shouldn't
be limited by system timer tick resolution, but with the underlying hardware
clock resolution.
> Things like TCP and DHCP could then be written so that they
> work with any system tick resolution.
>
> If there were macros to convert between "real-world" time and
> system ticks, how many places would those need to be inserted
> for an eCos system to "just work" when the system timer
> resolution is changed?
>
> Would a change like this make it into the standard source tree?
>
I believe that eCos community would benefit from this change.
> If not, I don't think I want to fork my own version and have to
> support it ad inifinitum -- I'll just have to tell those
> customers they're out of luck if they don't like 10ms timer
> ticks.
>
> --
> Grant Edwards
> grante@visi.com
>
Best regards,
Jurica Baricevic