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Date:	Sat, 11 Jul 2015 15:04:52 +0000
From:	Chris Metcalf <cmetcalf@...hip.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] nohz: prevent tilegx network driver interrupts


> On Jul 11, 2015, at 10:44 AM, Frederic Weisbecker <fweisbec@...il.com> wrote:
> 
>> On Fri, Jul 10, 2015 at 03:37:25PM -0400, Chris Metcalf wrote:
>> Normally the tilegx networking shim sends irqs to all the cores
>> to distribute the load of processing incoming-packet interrupts,
>> so that you can get to multiple Gb's of traffic inbound.
>> 
>> However, in nohz_full mode we don't want to interrupt the
>> nohz_full cores by default, so we limit the set of cores we use
>> to only the online housekeeping cores.
>> 
>> To make client code easier to read, we introduce a new nohz_full
>> accessor, housekeeping_cpumask(), which returns a pointer to the
>> housekeeping_mask if nohz_full is enabled, and otherwise returns
>> the cpu_possible_mask.
>> 
>> Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>
> 
> Looks good. Since it modifies nohz core stuff, do you mind if I take it?
> 
> Thanks. 

Sure, that's fine. Thanks. 

> 
>> ---
>> drivers/net/ethernet/tile/tilegx.c | 4 +++-
>> include/linux/tick.h               | 9 +++++++++
>> 2 files changed, 12 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/net/ethernet/tile/tilegx.c b/drivers/net/ethernet/tile/tilegx.c
>> index a3f7610002aa..0a15acc075b3 100644
>> --- a/drivers/net/ethernet/tile/tilegx.c
>> +++ b/drivers/net/ethernet/tile/tilegx.c
>> @@ -40,6 +40,7 @@
>> #include <linux/tcp.h>
>> #include <linux/net_tstamp.h>
>> #include <linux/ptp_clock_kernel.h>
>> +#include <linux/tick.h>
>> 
>> #include <asm/checksum.h>
>> #include <asm/homecache.h>
>> @@ -2273,7 +2274,8 @@ static int __init tile_net_init_module(void)
>>        tile_net_dev_init(name, mac);
>> 
>>    if (!network_cpus_init())
>> -        network_cpus_map = *cpu_online_mask;
>> +        cpumask_and(&network_cpus_map, housekeeping_cpumask(),
>> +                cpu_online_mask);
>> 
>>    return 0;
>> }
>> diff --git a/include/linux/tick.h b/include/linux/tick.h
>> index 3741ba1a652c..d3b00f0b2221 100644
>> --- a/include/linux/tick.h
>> +++ b/include/linux/tick.h
>> @@ -160,6 +160,15 @@ static inline void tick_nohz_full_kick_all(void) { }
>> static inline void __tick_nohz_task_switch(struct task_struct *tsk) { }
>> #endif
>> 
>> +static inline const struct cpumask *housekeeping_cpumask(void)
>> +{
>> +#ifdef CONFIG_NO_HZ_FULL
>> +    if (tick_nohz_full_enabled())
>> +        return housekeeping_mask;
>> +#endif
>> +    return cpu_possible_mask;
>> +}
>> +
>> static inline bool is_housekeeping_cpu(int cpu)
>> {
>> #ifdef CONFIG_NO_HZ_FULL
>> -- 
>> 2.1.2
>> 
--
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