linux-kernel - Re: [PATCH] hugetlb: Add nohugepages parameter to prevent hugepages creation

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Message-ID: <2d593c95-3c69-8f50-17ff-223bd607caf1@gpiccoli.net>
Date:   Tue, 15 Oct 2019 11:09:53 -0300
From:   "Guilherme G. Piccoli" <guilherme@...ccoli.net>
To:     Michal Hocko <mhocko@...nel.org>, Qian Cai <cai@....pw>
Cc:     Guilherme Piccoli <gpiccoli@...onical.com>, linux-mm@...ck.org,
        mike.kravetz@...cle.com, linux-kernel@...r.kernel.org,
        Jay Vosburgh <jay.vosburgh@...onical.com>,
        "Guilherme G. Piccoli" <kernel@...ccoli.net>
Subject: Re: [PATCH] hugetlb: Add nohugepages parameter to prevent hugepages
 creation



On 10/15/19 11:05 AM, Michal Hocko wrote:
> On Tue 15-10-19 10:58:36, Guilherme G. Piccoli wrote:
>> On 10/15/19 9:18 AM, Michal Hocko wrote:
>>> I do agree with Qian Cai here. Kdump kernel requires a very tailored
>>> environment considering it is running in a very restricted
>>> configuration. The hugetlb pre-allocation sounds like a tooling problem
>>> and should be fixed at that layer.
>>>
>>
>> Hi Michal, thanks for your response. Can you suggest me a current way of
>> preventing hugepages for being created, using userspace? The goal for this
>> patch is exactly this, introduce such a way.
> 
> Simply restrict the environment to not allocate any hugepages? Kdump
> already controls the kernel command line and it also starts only a very
> minimal subset of services. So who is allocating those hugepages?
> sysctls should be already excluded by default as Qian mentioned.
> 


OK, thanks Michal and Qian, I'll try to make things work from kdump 
perspective. The trick part is exactly preventing the sysctl to get 
applied heh

Cheers,


Guilherme