[Xen-devel] Re: [GIT/PATCH v4] xen network backend driver

[Ben Hutchings <bhutchings@xxxxxxxxxxxxxx>]

On Thu, 2011-03-10 at 09:15 -0800, Stephen Hemminger wrote:
> On Thu, 10 Mar 2011 17:02:33 +0000
> Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> > +struct xenvif {
> > +   /* Unique identifier for this interface. */
> ...
> > +   struct net_device_stats stats;
> > +
> 
> There is already a stats struct in net_device in current kernel
> versions, unless there is a compelling reason otherwise
> please use that.
> 
> Also, you probably want to implement per-cpu and 64 bit
> stats.

The driver is using a single queue, so I don't see what benefit it would
get from per-cpu stats.  At some point it should become multiqueue and
then it should store per-queue stats.

64-bit stats are definitely preferable, but since they're being
maintained on the data path this may require some significant work.
(Ian: see <linux/u64_stats_sync.h> for the canonical way to do this.)
Given that only a relatively few existing drivers do this (I count 13),
I'm not sure we can reasonably demand that a new driver does - yet.

Ben.

-- 
Ben Hutchings, Senior Software 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.


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