netdev - Re: [PATCH net-next] net: bridge: add STP xstats

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Message-ID: <20191210153441.GB1429230@t480s.localdomain>
Date:   Tue, 10 Dec 2019 15:34:41 -0500
From:   Vivien Didelot <vivien.didelot@...il.com>
To:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH net-next] net: bridge: add STP xstats

On Tue, 10 Dec 2019 22:15:26 +0200, Nikolay Aleksandrov <nikolay@...ulusnetworks.com> wrote:
> >>>> Why do you need percpu ? All of these seem to be incremented with the
> >>>> bridge lock held. A few more comments below.
> >>>
> >>> All other xstats are incremented percpu, I simply followed the pattern.
> >>>
> >>
> >> We have already a lock, we can use it and avoid the whole per-cpu memory handling.
> >> It seems to be acquired in all cases where these counters need to be changed.
> > 
> > Since the other xstats counters are currently implemented this way, I prefer
> > to keep the code as is, until we eventually change them all if percpu is in
> > fact not needed anymore.
> > 
> > The new series is ready and I can submit it now if there's no objection.
> 
> There is a reason other counters use per-cpu - they're incremented without any locking from fast-path.
> The bridge STP code already has a lock which is acquired in all of these paths and we don't need
> this overhead and the per-cpu memory allocations. Unless you can find a STP codepath which actually
> needs per-cpu, I'd prefer you drop it.

Ho ok I understand what you mean now. I'll drop the percpu attribute.


Thanks,

	Vivien