Date: Mon, 23 Feb 2015 21:50:52 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Aaron Tomlin <atomlin@redhat.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Davidlohr Bueso <dave@stgolabs.net>,
        David Rientjes <rientjes@google.com>,
        "David S. Miller" <davem@davemloft.net>,
        Fabian Frederick <fabf@skynet.be>, Guenter Roeck <linux@roeck-us.net>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>,
        Jens Axboe <axboe@fb.com>, Joe Perches <joe@perches.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Kees Cook <keescook@chromium.org>,
        Michael Marineau <mike@marineau.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Prarit Bhargava <prarit@redhat.com>, Rik van Riel <riel@redhat.com>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vladimir Davydov <vdavydov@parallels.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/4 v4] kernel/fork.c: memory hotplug updates
	max_threads
Message-ID: <20150223205052.GA26955@redhat.com>
References: <20150222075825.GA20626@gmail.com> <1424722477-23758-1-git-send-email-xypron.glpk@gmx.de> <1424722477-23758-5-git-send-email-xypron.glpk@gmx.de>
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On 02/23, Heinrich Schuchardt wrote:
>
> +static int memory_hotplug_callback(struct notifier_block *self,
> +				   unsigned long action, void *arg)
> +{
> +	switch (action) {
> +	case MEM_ONLINE:
> +		/*
> +		 * If memory was added, try to maximize the number of allowed
> +		 * threads.
> +		 */
> +		set_max_threads(UINT_MAX);
> +		break;
> +	case MEM_OFFLINE:
> +		/*
> +		 * If memory was removed, try to keep current value.
> +		 */
> +		set_max_threads(max_threads);
> +		break;
> +	}

can't understand... set_max_threads() added by 1/4 ignore its argument.
Why does it need "int max_threads_suggested" then?

And it changes the swapper/0's rlimits. This is pointless after we fork
/sbin/init.

It seems to me these patches need some cleanups. Plus I am not sure the
kernel should update max_threads automatically, we have the "threads-max"
sysctl.

Oleg.

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