netdev - Re: [PATCH] net: tracepoint: fix print wrong sysctl

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Date:   Mon, 7 Sep 2020 10:50:30 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Dust Li <dust.li@...ux.alibaba.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Satoru Moriya <satoru.moriya@....com>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: tracepoint: fix print wrong sysctl_mem value

On Mon,  7 Sep 2020 22:47:57 +0800 Dust Li wrote:
> sysctl_mem is an point, and tracepoint entry do not support
> been visited like an array. Use 3 long type to get sysctl_mem
> instead.
> 
> tracpoint output with and without this fix:
> - without fix:
>    28821.074 sock:sock_exceed_buf_limit:proto:UDP
>    sysctl_mem=-1741233440,19,322156906942464 allocated=19 sysctl_rmem=4096
>    rmem_alloc=75008 sysctl_wmem=4096 wmem_alloc=1 wmem_queued=0
>    kind=SK_MEM_RECV
> 
> - with fix:
>   2126.136 sock:sock_exceed_buf_limit:proto:UDP
>   sysctl_mem=18,122845,184266 allocated=19 sysctl_rmem=4096
>   rmem_alloc=73728 sysctl_wmem=4096 wmem_alloc=1 wmem_queued=0
>   kind=SK_MEM_RECV
> 
> Fixes: 3847ce32aea9fdf ("core: add tracepoints for queueing skb to rcvbuf")
> Signed-off-by: Dust Li <dust.li@...ux.alibaba.com>
> ---
>  include/trace/events/sock.h | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/include/trace/events/sock.h b/include/trace/events/sock.h
> index a966d4b5ab37..9118dd2353b7 100644
> --- a/include/trace/events/sock.h
> +++ b/include/trace/events/sock.h
> @@ -98,7 +98,9 @@ TRACE_EVENT(sock_exceed_buf_limit,
>  
>  	TP_STRUCT__entry(
>  		__array(char, name, 32)
> -		__field(long *, sysctl_mem)
> +		__field(long, sysctl_mem0)
> +		__field(long, sysctl_mem1)
> +		__field(long, sysctl_mem2)

Why not make it an __array() ?

>  		__field(long, allocated)
>  		__field(int, sysctl_rmem)
>  		__field(int, rmem_alloc)