Re: [RFC] Dynamic Tick and Deferrable Timer Support

From: Andrew Morton
Date: Thu Jan 15 2009 - 01:16:40 EST


On Wed, 14 Jan 2009 14:03:09 -0600 "Hunter, Jon" <jon-hunter@xxxxxx> wrote:

> Hello All,
>
> I have been working to maximise the kernel sleep time on an embedded device by utilising the dynamic tick and deferrable timer features.
>
> During the course of this work I found that although timers were configured as deferrable, only timers for time interval tv1 were actually being deferred. Reviewing the deferrable timer patch [1], it does appear that the code is written to only defer timers for interval tv1. Therefore, I wanted to ask if this is intentional or not?
>
> I have applied the below patch to defer all deferrable timers regardless of interval and so far it is working on the embedded device. I wanted to share this in case this could be something that could be applied to the mainline.
>
> Please excuse any foolish mistakes I may have made here as this is my first post to your mailing list. Any feedback you could offer would be appreciated.
>
> Cheers
> Jon
>
> [1] Deferrable timer patch: http://marc.info/?l=linux-kernel&m=117512286417320&w=2
>
>
> Signed-off-by: Jon Hunter <jon-hunter@xxxxxx>
> ---
> kernel/timer.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/timer.c b/kernel/timer.c
> index dee3f64..76a3ac6 100644
> --- a/kernel/timer.c
> +++ b/kernel/timer.c
> @@ -930,6 +930,9 @@ cascade:
> index = slot = timer_jiffies & TVN_MASK;
> do {
> list_for_each_entry(nte, varp->vec + slot, entry) {
> + if (tbase_get_deferrable(nte->base))
> + continue;
> +
> found = 1;
> if (time_before(nte->expires, expires))
> expires = nte->expires;

Venki, could you please take a look?
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