Subject: Re: [PATCH 5/6] tuntap: per queue 64 bit stats

From: Jason Wang <[email-masked]>
Date: Tue, 26 Jun 2012 14:28:28 +0800

On 06/26/2012 02:10 PM, Eric Dumazet wrote:
> On Tue, 2012-06-26 at 14:00 +0800, Jason Wang wrote:
>
>> Yes, looks like it's hard to use NETIF_F_LLTX without breaking the u64
>> statistics, may worth to use tx lock and alloc_netdev_mq().
> Yes, this probably needs percpu storage (if you really want to use
> include/linux/u64_stats_sync.h).
>
> But percpu storage seems a bit overkill with a raising number of cpus
> on typical machines.
>
> For loopback device, its fine because we only have one lo device per
> network namespace, and some workloads really hit hard this device.
>
> But for tuntap, I am not sure ?
>

The problem is that we want to collect per-queue statistics. So if we 
convert tuntap to use alloc_netdev_mq(), the tx statistics would be 
updated under tx lock which looks safe.

>
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