From: "Brown, Len" <len.brown@intel.com>
To: Prarit Bhargava <prarit@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>
CC: "Semin, Andrey" <andrey.semin@intel.com>
Subject: RE: [PATCH 2/2] turbostat, add set_base_cpu()
Thread-Topic: [PATCH 2/2] turbostat, add set_base_cpu()
Thread-Index: AQHQlIcG1PMkkNtSxkyAPYW9nu1fwJ2IJFbA
Date: Fri, 22 May 2015 15:55:15 +0000
Message-ID: <1A7043D5F58CCB44A599DFD55ED4C9484688E5F2@fmsmsx115.amr.corp.intel.com>
References: <1432296063-22185-1-git-send-email-prarit@redhat.com>
 <1432296063-22185-3-git-send-email-prarit@redhat.com>
In-Reply-To: <1432296063-22185-3-git-send-email-prarit@redhat.com>
Accept-Language: en-US
Content-Language: en-US
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 8BIT
MIME-Version: 1.0
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 997
Lines: 36

> +void set_base_cpu(void)
> +{
> +	int cpu;
> +
> +	for (cpu = 0; cpu <= topo.max_cpu_num; ++cpu) {
> +		if (cpu_is_not_present(cpu))
> +			continue;
> +		base_cpu = cpu;
> +		break;
> +	}
> +
> +	if (base_cpu == -1)
> +		err(-ENODEV, "No valid cpus found");
> +}


cpu0 hard-coding is indeed arbitrary.
However, so is this proposed replacement, base_cpu.
Either may not match where turbostat is currently running,
and thus could provoke unnecessary cross-calls to get there.

I think it would be better to ask getcpu(2) where we are already running,
and simply use that one.  I think we can call it once and cache it,
as you proposed, rather than multiple system calls.

thanks,
-Len

ps. patches to turbostat should go to linux-pm@vger.kernel.org


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/