Re: [PATCH 0/4] cgroup/cpuset: Allow cpuset to bound displayed cpu info

From: Waiman Long <llong@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Iurii Zaikin <yzaikin@google.com>,
	x86@kernel.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 0/4] cgroup/cpuset: Allow cpuset to bound displayed cpu info
Date: Mon, 14 Jun 2021 22:53:53 -0400	[thread overview]
Message-ID: <0e21f16d-d91b-7cec-d832-4c401a713b10@redhat.com> (raw)
In-Reply-To: <YMe/cGV4JPbzFRk0@slm.duckdns.org>

On 6/14/21 4:43 PM, Tejun Heo wrote:
> Hello,
>
> On Mon, Jun 14, 2021 at 11:23:02AM -0400, Waiman Long wrote:
>> The current container management system is able to create the illusion
>> that applications running within a container have limited resources and
>> devices available for their use. However, one thing that is hard to hide
>> is the number of CPUs available in the system. In fact, the container
>> developers are asking for the kernel to provide such capability.
>>
>> There are two places where cpu information are available for the
>> applications to see - /proc/cpuinfo and /sys/devices/system/cpu sysfs
>> directory.
>>
>> This patchset introduces a new sysctl parameter cpuset_bound_cpuinfo
>> which, when set, will limit the amount of information disclosed by
>> /proc/cpuinfo and /sys/devices/system/cpu.
> The goal of cgroup has never been masquerading system information so that
> applications can pretend that they own the whole system and the proposed
> solution requires application changes anyway. The information being provided
> is useful but please do so within the usual cgroup interface - e.g.
> cpuset.stat. The applications (or libraries) that want to determine its
> confined CPU availability can locate the file through /proc/self/cgroup.

Thanks for your comment. I understand your point making change via 
cgroup interface files. However, this is not what the customers are 
asking for. They are using tools that look at /proc/cpuinfo and the 
sysfs files. It is a much bigger effort to make all those tools look at 
a new cgroup file interface instead. It can be more efficiently done at 
the kernel level.

Anyway, I am OK if the consensus is that it is not a kernel problem and 
have to be handled in userspace.

BTW, do you have any comment on another cpuset patch that I sent a week 
earlier?

https://lore.kernel.org/lkml/20210603212416.25934-1-longman@redhat.com/

I am looking forward for your feedback.

Cheers,
Longman