From: Namhyung Kim <namhyung@kernel.org>
To: David Ahern <dsahern@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Perf Users <linux-perf-users@vger.kernel.org>,
kernel-team@lge.com
Subject: Re: perf probe and bitfields
Date: Fri, 26 Jan 2018 15:56:56 +0900 [thread overview]
Message-ID: <20180126065656.GD22737@sejong> (raw)
In-Reply-To: <52f06b83-1065-dc88-756e-7f8fffc5c21e@gmail.com>
Hi David,
On Fri, Jan 19, 2018 at 08:43:50AM -0800, David Ahern wrote:
> Hi Arnaldo / Masami:
>
> Are there known issues / limitations with perf probe and bitfields?
>
> Here's an example: pkt_type is a bitfield in sk_buff. When I put a probe
> in arp_rcv to examine the pkt_type value:
>
> $ perf probe 'arp_rcv ptype=skb->pkt_type dev=dev->name:string'
Bitfield type takes 3 parameters according to the Doc/perf-probe.txt.
Maybe it's like 'ptype=skb->pkt_type:b3@0/8' ?
Thanks,
Namhyung
>
> I only get '0' output:
>
> $ perf script
> vhost-27472 27483 [013] 4313207.619714: probe:arp_rcv:
> (ffffffff815653b0) ptype=0 dev="br1"
> vhost-27472 27483 [013] 4313207.619763: probe:arp_rcv:
> (ffffffff815653b0) ptype=0 dev="br1"
> vhost-27472 27483 [013] 4313210.588990: probe:arp_rcv:
> (ffffffff815653b0) ptype=0 dev="br1"
>
> when I know broadcast packet are getting handled (pkt_type ==
> PACKET_BROADCAST). This is confirmed by adding a printk to arp_rcv.
>
> Thanks,
> David
> --
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next prev parent reply other threads:[~2018-01-26 6:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-19 16:43 perf probe and bitfields David Ahern
2018-01-26 6:56 ` Namhyung Kim [this message]
2018-01-26 16:28 ` David Ahern
2018-01-27 5:04 ` Masami Hiramatsu
2018-01-30 16:53 ` David Ahern
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