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Subject: Re: [PATCH net-next v5 07/10] forcedeth: implement
 ndo_get_stats64() API
From: Ben Hutchings <bhutchings@solarflare.com>
To: Stephen Hemminger <shemminger@vyatta.com>
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Organization: Solarflare Communications
Date: Wed, 16 Nov 2011 17:14:54 +0000
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On Wed, 2011-11-16 at 08:55 -0800, Stephen Hemminger wrote:
> On Tue, 15 Nov 2011 21:15:55 -0800
> David Decotigny <david.decotigny@google.com> wrote:
> 
> > This commit implements the ndo_get_stats64() API for forcedeth. Since
> > these stats are being updated from different contexts (process and
> > timer), this commit adds protection (locking + atomic variables).
> > 
> > Tested:
> >   - 16-way SMP x86_64 ->
> >     RX bytes:7244556582 (7.2 GB)  TX bytes:181904254 (181.9 MB)
> >   - pktgen + loopback: identical rx_bytes/tx_bytes and rx_packets/tx_packets
> 
> Rather than adding additional locking why not use a percpu structure
> to hold statistics. See loopback, macvlan, veth, xen-netfront.

percpu is stupid for a single-queue driver.

> Or realize that the Tx side is single threaded by dev->xmit_lock already
> and the Rx side is single threaded by NAPI.

Right.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.