linux-kernel - Re: [PATCH v2 net-next 07/26] mvneta: add .ndo_get_xdp

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Date:   Thu, 25 Nov 2021 18:16:49 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
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        Saeed Bishara <saeedb@...zon.com>,
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        Claudiu Manoil <claudiu.manoil@....com>,
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        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 net-next 07/26] mvneta: add .ndo_get_xdp_stats() callback

From: Russell King (Oracle) <linux@...linux.org.uk>
Date: Wed, 24 Nov 2021 11:39:05 +0000

> On Tue, Nov 23, 2021 at 05:39:36PM +0100, Alexander Lobakin wrote:
> > +	for_each_possible_cpu(cpu) {
> > +		const struct mvneta_pcpu_stats *stats;
> > +		const struct mvneta_stats *ps;
> > +		u64 xdp_xmit_err;
> > +		u64 xdp_redirect;
> > +		u64 xdp_tx_err;
> > +		u64 xdp_pass;
> > +		u64 xdp_drop;
> > +		u64 xdp_xmit;
> > +		u64 xdp_tx;
> > +		u32 start;
> > +
> > +		stats = per_cpu_ptr(pp->stats, cpu);
> > +		ps = &stats->es.ps;
> > +
> > +		do {
> > +			start = u64_stats_fetch_begin_irq(&stats->syncp);
> > +
> > +			xdp_drop = ps->xdp_drop;
> > +			xdp_pass = ps->xdp_pass;
> > +			xdp_redirect = ps->xdp_redirect;
> > +			xdp_tx = ps->xdp_tx;
> > +			xdp_tx_err = ps->xdp_tx_err;
> > +			xdp_xmit = ps->xdp_xmit;
> > +			xdp_xmit_err = ps->xdp_xmit_err;
> > +		} while (u64_stats_fetch_retry_irq(&stats->syncp, start));
> > +
> > +		xdp_stats->drop += xdp_drop;
> > +		xdp_stats->pass += xdp_pass;
> > +		xdp_stats->redirect += xdp_redirect;
> > +		xdp_stats->tx += xdp_tx;
> > +		xdp_stats->tx_errors += xdp_tx_err;
> > +		xdp_stats->xmit_packets += xdp_xmit;
> > +		xdp_stats->xmit_errors += xdp_xmit_err;
> 
> Same comment as for mvpp2 - this could share a lot of code from
> mvneta_ethtool_update_pcpu_stats() (although it means we end up
> calculating a little more for the alloc error and refill error
> that this API doesn't need) but I think sharing that code would be
> a good idea.

Ah, I didn't do that because in my first series I was removing
Ethtool counters at all. In this one, I left them as-is due to
some of folks hinted me that those counters (not specifically
on mvpp2 or mvneta, let's say on virtio-net or so) could have
already been used in some admin scripts somewhere in the world
(but with a TODO to figure out which driver I could remove them
in and do that).
It would be great if you know and would hint me if I could remove
those XDP-related Ethtool counters from Marvell drivers or not.
If so, I'll wipe them, otherwise just factor out common parts to
wipe out code duplication.

> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

Thanks,
Al