From: Eric Dumazet <eric.dumazet@gmail.com>
To: Zhu Yanjun <yanjun.zhu@oracle.com>,
netdev@vger.kernel.org, davem@davemloft.net,
nan.1986san@gmail.com
Subject: Re: [PATCH 1/1] forcedeth: use per cpu to collect xmit/recv statistics
Date: Fri, 30 Aug 2019 11:32:33 +0200 [thread overview]
Message-ID: <24ad8394-cb24-fcb7-0dc2-3435429bb8cd@gmail.com> (raw)
In-Reply-To: <1567154111-23315-2-git-send-email-yanjun.zhu@oracle.com>
On 8/30/19 10:35 AM, Zhu Yanjun wrote:
> When testing with a background iperf pushing 1Gbit/sec traffic and running
> both ifconfig and netstat to collect statistics, some deadlocks occurred.
>
This is quite a heavy patch trying to fix a bug...
I suspect the root cause has nothing to do with stat
collection since on 64bit arches there is no additional synchronization.
(u64_stats_update_begin(), u64_stats_update_end() are nops)
> +static inline void nv_get_stats(int cpu, struct fe_priv *np,
> + struct rtnl_link_stats64 *storage)
> +{
> + struct nv_txrx_stats *src = per_cpu_ptr(np->txrx_stats, cpu);
> + unsigned int syncp_start;
> +
> + do {
> + syncp_start = u64_stats_fetch_begin_irq(&np->swstats_rx_syncp);
> + storage->rx_packets += src->stat_rx_packets;
> + storage->rx_bytes += src->stat_rx_bytes;
> + storage->rx_dropped += src->stat_rx_dropped;
> + storage->rx_missed_errors += src->stat_rx_missed_errors;
> + } while (u64_stats_fetch_retry_irq(&np->swstats_rx_syncp, syncp_start));
> +
> + do {
> + syncp_start = u64_stats_fetch_begin_irq(&np->swstats_tx_syncp);
> + storage->tx_packets += src->stat_tx_packets;
> + storage->tx_bytes += src->stat_tx_bytes;
> + storage->tx_dropped += src->stat_tx_dropped;
> + } while (u64_stats_fetch_retry_irq(&np->swstats_tx_syncp, syncp_start));
> +}
> +
>
This is buggy :
If the loops are ever restarted, the storage->fields will have
been modified multiple times.
next prev parent reply other threads:[~2019-08-30 9:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 8:35 [PATCH 0/1] Fix deadlock problem and make performance better Zhu Yanjun
2019-08-30 8:35 ` [PATCH 1/1] forcedeth: use per cpu to collect xmit/recv statistics Zhu Yanjun
2019-08-30 9:32 ` Eric Dumazet [this message]
2019-08-31 4:24 ` Zhu Yanjun
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=24ad8394-cb24-fcb7-0dc2-3435429bb8cd@gmail.com \
--to=eric.dumazet@gmail.com \
--cc=davem@davemloft.net \
--cc=nan.1986san@gmail.com \
--cc=netdev@vger.kernel.org \
--cc=yanjun.zhu@oracle.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).