linux-kernel - Re: [PATCH] debugobjects: add a new Kconfig for POOL

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Date:   Mon, 19 Nov 2018 11:32:38 -0500
From:   Qian Cai <cai@....us>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Waiman Long <longman@...hat.com>
Cc:     linux kernel <linux-kernel@...r.kernel.org>, arnd@...db.de,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yang Shi <yang.shi@...ux.alibaba.com>
Subject: Re: [PATCH] debugobjects: add a new Kconfig for POOL_SIZE

On Mon, 2018-11-19 at 17:25 +0100, Thomas Gleixner wrote:
> 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.
> 
Ah, I thought you meant the NR_CPUS macro. It is CONFIG_NR_CPUS, and we are
on the same page.