Re: [PATCH v2] nohz: prevent tilegx network driver interrupts

Frederic Weisbecker
2015-07-11T14:44:45Z

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@ezchip.com>

Looks good. Since it modifies nohz core stuff, do you mind if I take it?

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
>