linux-kernel - Re: [PATCH v9 3/8] hugetlb_cgroup: add reservation accounting for private mappings

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Date:   Fri, 17 Jan 2020 14:09:42 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Mina Almasry <almasrymina@...gle.com>
Cc:     shuah <shuah@...nel.org>, David Rientjes <rientjes@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Greg Thelen <gthelen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org, cgroups@...r.kernel.org,
        Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
        Michal Koutný <mkoutny@...e.com>,
        Hillf Danton <hdanton@...a.com>
Subject: Re: [PATCH v9 3/8] hugetlb_cgroup: add reservation accounting for
 private mappings

On 1/14/20 2:52 PM, Mina Almasry wrote:
> On Mon, Jan 13, 2020 at 4:55 PM Mike Kravetz <mike.kravetz@...cle.com> wrote:
>>> +#ifdef CONFIG_CGROUP_HUGETLB
>>> +     /*
>>> +      * Since we check for HPAGE_RESV_OWNER above, this must a private
>>> +      * mapping, and these values should be none-zero, and should point to
>>> +      * the hugetlb_cgroup counter to uncharge for this reservation.
>>> +      */
>>> +     WARN_ON(!resv->reservation_counter);
>>> +     WARN_ON(!resv->pages_per_hpage);
>>> +     WARN_ON(!resv->css);
>>
>> I was once again wondering if these were always non-NULL for private mappings.
>> It seems that reservation_counter (h_gc) would be NULL in these cases from
>> these early checks in hugetlb_cgroup_charge_cgroup().
>>
> 
> You are right. I'm fixing in v10 the code and comments to account for
> h_cg potentially being NULL, but I'm having trouble testing. Looking
> at the code, I'm a bit confused by the checks. Seems to me
> hugetlb_cgroup_disabled() is the same as #ifdef CONFIG_CGROUP_HUGETLB;
> I can't find a way to enable the Kconfig but have that return false
> unless I hack the code.

What about the boot options?

cgroup_disable=
cgroup_no_v1=

-- 
Mike Kravetz