netdev - Re: [PATCH v2] Receive Packet Steering

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Message-ID: <49FE86F0.4070206@cosmosbay.com>
Date:	Mon, 04 May 2009 08:10:56 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Tom Herbert <therbert@...gle.com>
CC:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: [PATCH v2] Receive Packet Steering

Eric Dumazet a écrit :
> Tom Herbert a écrit :
>> This is an update of the receive packet steering patch (RPS) based on received
>> comments (thanks for all the comments).  Improvements are:
>>
>> 1) Removed config option for the feature.
>> 2) Made scheduling of backlog NAPI devices between CPUs lockless and much
>> simpler.
>> 3) Added new softirq to do defer sending IPIs for coalescing.
>> 4) Imported hash from simple_rx_hash.  Eliminates modulo operation to convert
>> hash to index.
>> 5) If no cpu is found for packet steering, then netif_receive_skb processes
>> packet inline as before without queueing.  In paritcular if RPS is not
>> configured on a device the receive path is unchanged from current for
>> NAPI devices (one additional conditional).
>>
>> Tom
> 

another error :

>> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>> index 2da59a0..073a407 100644
>> --- a/net/core/net-sysfs.c
>> +++ b/net/core/net-sysfs.c
>> @@ -211,6 +211,63 @@ static ssize_t store_tx_queue_len(struct device *dev,
>>  	return netdev_store(dev, attr, buf, len, change_tx_queue_len);
>>  }
>>
>> +static ssize_t store_rps_cpus(struct device *dev,
>> +			      struct device_attribute *attr,
>> +			      const char *buf, size_t len)
>> +{
>> +	struct net_device *net = to_net_dev(dev);
>> +	cpumask_t mask;
>> +	int err, cpu;
>> +	int i = 0;
>> +
>> +	if (!capable(CAP_NET_ADMIN))
>> +		return -EPERM;
>> +
>> +	err = bitmap_parse(buf, len, cpumask_bits(&mask), nr_cpumask_bits);
>> +	if (err)
>> +		return err;
>> +
>> +	rtnl_lock();
>> +	if (dev_isalive(net)) {
>> +		if (!net->rps_map) {
>> +			net->rps_map = kzalloc(sizeof(u16) *
>> +			    num_possible_cpus(), GFP_KERNEL);
> 
> num_possible_cpus() is not the max index of a cpu, but the number of possible cpus.
> it can be for example 2, but cpu0 being index 0, and second cpu at index 511
> 
> So I believe you want nr_cpu_ids here
> 
> (num_possible_cpus() <= nr_cpu_ids), not necessarly equal. 
> 
> 
>> +			if (!net->rps_map)

lacks a rtnl_unlock() here, before return

>> +				return -ENOMEM;
>> +		}
>> +		cpus_and(mask, mask, cpu_online_map);
>> +		for_each_cpu_mask(cpu, mask)
>> +			net->rps_map[i++] =  cpu;
>> +		net->rps_map_len = i;
>> +	}
>> +	rtnl_unlock();
>> +
>> +	return len;
>> +}
>> +


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