On 12/27/2016 05:47 PM, Marcelo Ricardo Leitner wrote:
> On Tue, Dec 27, 2016 at 09:25:47AM +0100, Matthias Tafelmeier wrote:
>> Oftenly, introducing side effects on packet processing on the other half
>> of the stack by adjusting one of TX/RX via sysctl is not desirable.
>> There are cases of demand for asymmetric, orthogonal configurability.
>>
>> This holds true especially for nodes where RPS for RFS usage on top is
>> configured and therefore use the 'old dev_weight'. This is quite a
>> common base configuration setup nowadays, even with NICs of superior
>> processing
>> support (e.g. aRFS).
>>
>> A good example use case are nodes acting as noSQL data bases with a
>> large number of tiny requests and rather fewer but large packets as
>> responses.
>> It's affordable to have large budget and rx dev_weights for the
>> requests. But as a side effect having this large a number on TX
>> processed in one run can overwhelm drivers.
>>
>> This patch therefore introduces an independent configurability via sysctl to
>> userland.
>> ---
>> include/linux/netdevice.h | 2 ++
>> net/core/dev.c | 4 +++-
>> net/core/sysctl_net_core.c | 14 ++++++++++++++
>> net/sched/sch_generic.c | 2 +-
>> 4 files changed, 20 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index 994f742..bb331e0 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -3795,6 +3795,8 @@ void netdev_stats_to_stats64(struct rtnl_link_stats64
>> *stats64,
>> extern int netdev_max_backlog;
>> extern int netdev_tstamp_prequeue;
>> extern int weight_p;
>> +extern int dev_w_rx_bias;
>> +extern int dev_w_tx_bias;
>>
>> bool netdev_has_upper_dev(struct net_device *dev, struct net_device
>> *upper_dev);
>> struct net_device *netdev_upper_get_next_dev_rcu(struct net_device *dev,
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 8db5a0b..0dcbd28 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -3428,6 +3428,8 @@ EXPORT_SYMBOL(netdev_max_backlog);
>> int netdev_tstamp_prequeue __read_mostly = 1;
>> int netdev_budget __read_mostly = 300;
>> int weight_p __read_mostly = 64; /* old backlog weight */
>> +int dev_w_rx_bias __read_mostly = 1; /* bias for backlog weight
>> */
>> +int dev_w_tx_bias __read_mostly = 1; /* bias for output_queue
>> quota */
>>
>> /* Called with irq disabled */
>> static inline void ____napi_schedule(struct softnet_data *sd,
>> @@ -4833,7 +4835,7 @@ static int process_backlog(struct napi_struct *napi,
>> int quota)
>> net_rps_action_and_irq_enable(sd);
>> }
>>
>> - napi->weight = weight_p;
>> + napi->weight = weight_p * dev_w_rx_bias;
>> while (again) {
>> struct sk_buff *skb;
>>
>> diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
>> index 2a46e40..a2ab149 100644
>> --- a/net/core/sysctl_net_core.c
>> +++ b/net/core/sysctl_net_core.c
>> @@ -276,6 +276,20 @@ static struct ctl_table net_core_table[] = {
>> .proc_handler = proc_dointvec
>> },
>> {
>> + .procname = "dev_w_rx_bias",
>> + .data = &dev_w_rx_bias,
>> + .maxlen = sizeof(int),
>> + .mode = 0644,
>> + .proc_handler = proc_dointvec
>> + },
>> + {
>> + .procname = "dev_w_tx_bias",
>> + .data = &dev_w_tx_bias,
>> + .maxlen = sizeof(int),
>> + .mode = 0644,
>> + .proc_handler = proc_dointvec
>> + },
>> + {
> Please describe these at Documentation/sysctl/net.txt, probably right
> after dev_weight.
Sure, I'll do that.> I'm not sure about the abbreviation, maybe it would be better the longer > name as it doesn't block tab completion. > dev_weight_tx_bias > dev_weight_rx_bias > dev_weight > Do not find the abbreviation/naming satisfactory, either. Rather saw them as a draft. Could think of dev_weight distant naming: ns_rps_cpu_rx_bias ns_cpu_tx_bias Though, makes me concerned about association etc. Maybe, that's nit picking.
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