netdev - Re: [PATCH net] random32: add a tracepoint for prandom

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Date:   Thu, 13 Aug 2020 15:16:45 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com, w@....eu,
        sedat.dilek@...il.com
Subject: Re: [PATCH net] random32: add a tracepoint for prandom_u32()

From: Eric Dumazet <edumazet@...gle.com>
Date: Thu, 13 Aug 2020 10:06:43 -0700

> There has been some heat around prandom_u32() lately, and some people
> were wondering if there was a simple way to determine how often
> it was used, before considering making it maybe 10 times more expensive.
> 
> This tracepoint exports the generated pseudo random value.
> 
> Tested:
> 
> perf list | grep prandom_u32
>   random:prandom_u32                                 [Tracepoint event]
> 
> perf record -a [-g] [-C1] -e random:prandom_u32 sleep 1
> [ perf record: Woken up 0 times to write data ]
> [ perf record: Captured and wrote 259.748 MB perf.data (924087 samples) ]
> 
> perf report --nochildren
>     ...
>     97.67%  ksoftirqd/1     [kernel.vmlinux]  [k] prandom_u32
>             |
>             ---prandom_u32
>                prandom_u32
>                |
>                |--48.86%--tcp_v4_syn_recv_sock
>                |          tcp_check_req
>                |          tcp_v4_rcv
>                |          ...
>                 --48.81%--tcp_conn_request
>                           tcp_v4_conn_request
>                           tcp_rcv_state_process
>                           ...
> perf script
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks Eric.