Re: [PATCH] debugobjects: add a new Kconfig for POOL_SIZE

From: Thomas Gleixner <tglx@linutronix.de>
To: Waiman Long <longman@redhat.com>
Cc: Qian Cai <cai@gmx.us>,
	linux kernel <linux-kernel@vger.kernel.org>,
	arnd@arndb.de, Andrew Morton <akpm@linux-foundation.org>,
	Yang Shi <yang.shi@linux.alibaba.com>
Subject: Re: [PATCH] debugobjects: add a new Kconfig for POOL_SIZE
Date: Mon, 19 Nov 2018 17:25:56 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.21.1811191722270.1669@nanos.tec.linutronix.de> (raw)
In-Reply-To: <0c6a79c8-dde2-dee9-efb0-5cf3d1b3949e@redhat.com>

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On Mon, 19 Nov 2018, Waiman Long wrote:
> On 11/19/2018 10:17 AM, Qian Cai wrote:
> > Right, I can remember that now . However, if I understand correctly, since the
> > early static pool size needs to be determined during the compilation time, it
> > depends on the No. CPUs are from the machines that built the distro kernels.
> > Then, when users use those distro kernels, they are not going to have correct
> > the pool size according to the No. CPUs on their test machines.
> 
> I see your point. Perhaps you can make ODEBUG_POOL_SIZE scales with
> CONFIG_NR_CPUS like
> 
> #define ODEBUG_POOL_SIZE    (1024 + CONFIG_NR_CPUS * 2)
> 
> CONFIG_NR_CPUS is usually set to a lot higher than the actual number of
> CPUs in a typical system. So you don't want to set the multiplier too high.

The number of CPUs on the build machine is totally irrelevant and not
influencing the build at all. The sizing solely depends on CONFIG_NR_CPUS.

And even if the initial pool is a bit oversized, it's init data and freed,
so no real harm done.

Thanks,

	tglx