linux-kernel - Re: [External] Re: [PATCH v15 4/8] mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page

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Date:   Thu, 18 Feb 2021 11:20:51 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org,
        Peter Zijlstra <peterz@...radead.org>, viro@...iv.linux.org.uk,
        Andrew Morton <akpm@...ux-foundation.org>, paulmck@...nel.org,
        mchehab+huawei@...nel.org, pawan.kumar.gupta@...ux.intel.com,
        Randy Dunlap <rdunlap@...radead.org>, oneukum@...e.com,
        anshuman.khandual@....com, jroedel@...e.de,
        Mina Almasry <almasrymina@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Oscar Salvador <osalvador@...e.de>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        David Hildenbrand <david@...hat.com>,
        HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Xiongchun duan <duanxiongchun@...edance.com>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [External] Re: [PATCH v15 4/8] mm: hugetlb: alloc the vmemmap
 pages associated with each HugeTLB page

On Thu, Feb 18, 2021 at 9:00 AM Mike Kravetz <mike.kravetz@...cle.com> wrote:
>
> On 2/17/21 12:13 AM, Michal Hocko wrote:
> > On Tue 16-02-21 11:44:34, Mike Kravetz wrote:
> > [...]
> >> If we are not going to do the allocations under the lock, then we will need
> >> to either preallocate or take the workqueue approach.
> >
> > We can still drop the lock temporarily right? As we already do before
> > calling destroy_compound_gigantic_page...
> >
>
> Yes we can.  I forgot about that.
>
> Actually, very little of what update_and_free_page does needs to be done
> under the lock.  Perhaps, just decrementing the global count and clearing
> the destructor so PageHuge() is no longer true.

Right. I have another question about using GFP flags. Michal
suggested using GFP_KERNEL instead of GFP_ATOMIC to
save reserve memory. From your last email, you suggested
using non-blocking allocation GFP flags (perhaps GFP_NOWAIT).

Hi Mike and Michal,

What is the consensus we finally reached? Thanks.