[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <7f1604fd-4bd6-4f16-8aed-2586afac7d15@lunn.ch>
Date: Fri, 10 Nov 2023 16:13:30 +0100
From: Andrew Lunn <andrew@...n.ch>
To: alexey.pakhunov@...cex.com
Cc: mchan@...adcom.com, vincent.wong2@...cex.com, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, siva.kallam@...adcom.com,
prashant@...adcom.com
Subject: Re: [PATCH v2 1/2] tg3: Move the [rt]x_dropped counters to tg3_napi
> @@ -11895,6 +11903,9 @@ static void tg3_get_nstats(struct tg3 *tp, struct rtnl_link_stats64 *stats)
> {
> struct rtnl_link_stats64 *old_stats = &tp->net_stats_prev;
> struct tg3_hw_stats *hw_stats = tp->hw_stats;
> + unsigned long rx_dropped;
> + unsigned long tx_dropped;
> + int i;
>
> stats->rx_packets = old_stats->rx_packets +
> get_stat64(&hw_stats->rx_ucast_packets) +
> @@ -11941,8 +11952,26 @@ static void tg3_get_nstats(struct tg3 *tp, struct rtnl_link_stats64 *stats)
> stats->rx_missed_errors = old_stats->rx_missed_errors +
> get_stat64(&hw_stats->rx_discards);
>
> - stats->rx_dropped = tp->rx_dropped;
> - stats->tx_dropped = tp->tx_dropped;
> + /* Aggregate per-queue counters. The per-queue counters are updated
> + * by a single writer, race-free. The result computed by this loop
> + * might not be 100% accurate (counters can be updated in the middle of
> + * the loop) but the next tg3_get_nstats() will recompute the current
> + * value so it is acceptable.
> + *
> + * Note that these counters wrap around at 4G on 32bit machines.
> + */
> + rx_dropped = (unsigned long)(old_stats->rx_dropped);
> + tx_dropped = (unsigned long)(old_stats->tx_dropped);
Isn't this wrapping artificial? old_stats is of type
rtnl_link_stats64, so the counters are 64 bit.
> +
> + for (i = 0; i < tp->irq_cnt; i++) {
> + struct tg3_napi *tnapi = &tp->napi[i];
> +
> + rx_dropped += tnapi->rx_dropped;
> + tx_dropped += tnapi->tx_dropped;
> + }
> +
> + stats->rx_dropped = rx_dropped;
> + stats->tx_dropped = tx_dropped;
state is also rtnl_link_stats64 so has 64 bit counters. So this code
is throwing away the upper 32 bits.
Why not use include/linux/u64_stats_sync.h, which should cost you
nothing on 64 bit machines, and do the right thing on 32 bit machines.
Andrew
Powered by blists - more mailing lists