Re: [PATCH] kretprobe events missing on 2-core KVM guest

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
To: wuqiang <wuqiang.matt@bytedance.com>
Cc: davem@davemloft.net, anil.s.keshavamurthy@intel.com,
	naveen.n.rao@linux.ibm.com, linux-kernel@vger.kernel.org,
	mattwu@163.com
Subject: Re: [PATCH] kretprobe events missing on 2-core KVM guest
Date: Wed, 26 Oct 2022 00:33:15 +0900	[thread overview]
Message-ID: <20221026003315.266d59d5c0780c2817be3a0d@kernel.org> (raw)
In-Reply-To: <20221025100117.18667-1-wuqiang.matt@bytedance.com>

On Tue, 25 Oct 2022 18:01:17 +0800
wuqiang <wuqiang.matt@bytedance.com> wrote:

> Default value of maxactive is set as num_possible_cpus() for nonpreemptable
> systems. For a 2-core system, only 2 kretprobe instances would be allocated
> in default, then these 2 instances for execve kretprobe are very likely to
> be used up with a pipelined command.
> 
> This patch increases the minimum of maxactive to 10.
> 

This looks reasonable to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thank you!

> Signed-off-by: wuqiang <wuqiang.matt@bytedance.com>
> ---
>  kernel/kprobes.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 3220b0a2fb4a..b781dee3f552 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2211,7 +2211,7 @@ int register_kretprobe(struct kretprobe *rp)
>  #ifdef CONFIG_PREEMPTION
>  		rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());
>  #else
> -		rp->maxactive = num_possible_cpus();
> +		rp->maxactive = max_t(unsigned int, 10, num_possible_cpus());
>  #endif
>  	}
>  #ifdef CONFIG_KRETPROBE_ON_RETHOOK
> -- 
> 2.34.1
> 

-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>