linux-kernel - [RFC] Dynamic Tick and Deferrable Timer Support

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Message-ID: <CF7665F795A4BE438425FE728CEACFA302F2436B52@dlee01.ent.ti.com>
Date:	Wed, 14 Jan 2009 14:03:09 -0600
From:	"Hunter, Jon" <jon-hunter@...com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [RFC] Dynamic Tick and Deferrable Timer Support

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@...com>
---
 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;
--
1.5.6.3
--
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