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Message-ID: <4A1300E3.1000809@cosmosbay.com>
Date: Tue, 19 May 2009 20:56:35 +0200
From: Eric Dumazet <dada1@...mosbay.com>
To: unlisted-recipients:; (no To-header on input)
CC: "Tero.Kristo@...ia.com" <Tero.Kristo@...ia.com>,
netdev@...r.kernel.org
Subject: [PATCH] net: use a deferred timer in rt_check_expire
Tero.Kristo@...ia.com a écrit :
>
>
>> -----Original Message-----
>> From: ext Eric Dumazet [mailto:dada1@...mosbay.com]
>> Sent: 19 May, 2009 12:04
>> To: Kristo Tero (Nokia-D/Tampere)
>> Cc: netdev@...r.kernel.org
>> Subject: Re: Network stack timer hacks for power saving
>>
>> Tero.Kristo@...ia.com a écrit :
>>> Hi,
>>>
>>> I have been looking at network stack timer optimization for power
>>> saving in embedded ARM environment, basically trying to
>> avoid as many
>>> wakeups as possible. I have changed several timers in the network
>>> stack into deferred ones, i.e. they do not wake up the
>> device from low
>>> power modes but instead they are deferred until next wakeup
>>from some
>>> other source, like another (non-deferred) timer or some I/O.
>> Attached
>>> a patch about the changes I've done, is something like this safe to
>>> do?
>>>
>>> -Tero
Here is the patch I cooked and tested on a machine where ip_rt_gc_interval
is set to minimal value (1 second), where equilibrium depends on garbage collection
done in time.
I found that delayed timers could be *really* delayed so I think we must take
into account the elapsed time (in jiffies) between two rt_check_expire()
calls, to "guarantee" a full scan of rt cache in a ip_rt_gc_timeout period.
Not for inclusion, as undergoing work is happening in this function
for a bug correction. I'll redo the patch later once stabilized.
[PATCH] net: use a deferred timer in rt_check_expire
For the sake of power saver lovers, use a deferrable timer to fire rt_check_expire()
As some big routers cache equilibrium depends on garbage collection done in time,
we take into account elapsed time between two rt_check_expire() invocations
to adjust the amount of slots we have to check.
Based on an initial idea and patch from Tero Kristo
Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
Signed-off-by: Tero Kristo <tero.kristo@...ia.com>
---
net/ipv4/route.c | 11 ++++++++---
1 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index c4c60e9..b2c6793 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -131,8 +131,8 @@ static int ip_rt_min_advmss __read_mostly = 256;
static int ip_rt_secret_interval __read_mostly = 10 * 60 * HZ;
static int rt_chain_length_max __read_mostly = 20;
-static void rt_worker_func(struct work_struct *work);
-static DECLARE_DELAYED_WORK(expires_work, rt_worker_func);
+static struct delayed_work expires_work;
+static unsigned long expires_ljiffies;
/*
* Interface to generic destination cache.
@@ -787,9 +787,12 @@ static void rt_check_expire(void)
struct rtable *rth, **rthp;
unsigned long length = 0, samples = 0;
unsigned long sum = 0, sum2 = 0;
+ unsigned long delta;
u64 mult;
- mult = ((u64)ip_rt_gc_interval) << rt_hash_log;
+ delta = jiffies - expires_ljiffies;
+ expires_ljiffies = jiffies;
+ mult = ((u64)delta) << rt_hash_log;
if (ip_rt_gc_timeout > 1)
do_div(mult, ip_rt_gc_timeout);
goal = (unsigned int)mult;
@@ -3410,6 +3413,8 @@ int __init ip_rt_init(void)
/* All the timers, started at system startup tend
to synchronize. Perturb it a bit.
*/
+ INIT_DELAYED_WORK_DEFERRABLE(&expires_work, rt_worker_func);
+ expires_ljiffies = jiffies;
schedule_delayed_work(&expires_work,
net_random() % ip_rt_gc_interval + ip_rt_gc_interval);
--
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