linux-kernel - Re: [PATCH 19/28] perf bench: Add epoll parallel epoll

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Message-ID: <b37610b7-f0a2-4556-bb2c-367440eb9bae@gmail.com>
Date: Mon, 29 Jul 2024 19:53:04 +0800
From: Like Xu <like.xu.linux@...il.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
 Davidlohr Bueso <dave@...olabs.net>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Ian Rogers <irogers@...gle.com>, Namhyung Kim <namhyung@...nel.org>,
 Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH 19/28] perf bench: Add epoll parallel epoll_wait benchmark

Hi guys,

On 11/22/18 11:36 AM, Arnaldo Carvalho de Melo wrote:
> +	/* default to the number of CPUs and leave one for the writer pthread */
> +	if (!nthreads)
> +		nthreads = cpu->nr - 1;

If there is only one CPU (e.g. a virtualized VM with only one vCPU),
what is the correct test model for epoll_wait benchmark ?

Is the behavior the same as using -t to explicitly specify 1:

	$ perf bench epoll wait -r 30 -t 1

or do we need:

     nthreads = max(perf_cpu_map__nr(cpu) - 1, 1);

?