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Message-ID: <CANn89iJKcKKLEXWELakScxxe8f0z1GQjmtA2UrBhqOEXQkk+9A@mail.gmail.com> Date: Mon, 24 Jan 2022 12:21:58 -0800 From: Eric Dumazet <edumazet@...gle.com> To: Cong Wang <xiyou.wangcong@...il.com> Cc: Jakub Kicinski <kuba@...nel.org>, Brian Vazquez <brianvv@...gle.com>, Jeffrey Ji <jeffreyjilinux@...il.com>, "David S . Miller" <davem@...emloft.net>, LKML <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org>, jeffreyji <jeffreyji@...gle.com> Subject: Re: [PATCH net-next] net-core: add InMacErrors counter On Mon, Jan 24, 2022 at 12:20 PM Cong Wang <xiyou.wangcong@...il.com> wrote: > > On Mon, Jan 24, 2022 at 09:29:24AM -0800, Jakub Kicinski wrote: > > On Mon, 24 Jan 2022 09:13:12 -0800 Brian Vazquez wrote: > > > On Fri, Jan 21, 2022 at 7:41 PM Jakub Kicinski <kuba@...nel.org> wrote: > > > > On Sat, 22 Jan 2022 00:03:01 +0000 Jeffrey Ji wrote: > > > > > From: jeffreyji <jeffreyji@...gle.com> > > > > > > > > > > Increment InMacErrors counter when packet dropped due to incorrect dest > > > > > MAC addr. > > > > > > > > > > example output from nstat: > > > > > \~# nstat -z "*InMac*" > > > > > \#kernel > > > > > Ip6InMacErrors 0 0.0 > > > > > IpExtInMacErrors 1 0.0 > > > > > > > > > > Tested: Created 2 netns, sent 1 packet using trafgen from 1 to the other > > > > > with "{eth(daddr=$INCORRECT_MAC...}", verified that nstat showed the > > > > > counter was incremented. > > > > > > > > > > Signed-off-by: jeffreyji <jeffreyji@...gle.com> > > > > > > > > How about we use the new kfree_skb_reason() instead to avoid allocating > > > > per-netns memory the stats? > > > > > > I'm not too familiar with the new kfree_skb_reason , but my > > > understanding is that it needs either the drop_monitor or ebpf to get > > > the reason from the tracepoint, right? This is not too different from > > > using perf tool to find where the pkt is being dropped. > > > > > > The idea here was to have a high level metric that is easier to find > > > for users that have less expertise on using more advance tools. > > > > That much it's understood, but it's a trade off. This drop point > > existed for 20 years, why do we need to consume extra memory now? > > kfree_skb_reason() is for tracing and tracing has overhead in > production, which is higher than just a percpu counter. > > What memory overhead are you talking about? We have ~37 IP related > SNMP counters, this patch merely adds 1/37 memory overhead. So, what's the > point? :-/ > BTW I just saw that kfree_skb_reason() changes have been proposed already by Menglong Dong this morning.
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