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From: Muchun Song <songmuchun@bytedance.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: "Jonathan Corbet" <corbet@lwn.net>,
	"Mike Kravetz" <mike.kravetz@oracle.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	bp@alien8.de, "X86 ML" <x86@kernel.org>,
	hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	paulmck@kernel.org, pawan.kumar.gupta@linux.intel.com,
	"Randy Dunlap" <rdunlap@infradead.org>,
	oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de,
	"Mina Almasry" <almasrymina@google.com>,
	"David Rientjes" <rientjes@google.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Michal Hocko" <mhocko@suse.com>,
	"Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
	"David Hildenbrand" <david@redhat.com>,
	"HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>,
	"Joao Martins" <joao.m.martins@oracle.com>,
	"Xiongchun duan" <duanxiongchun@bytedance.com>,
	fam.zheng@bytedance.com, linux-doc@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	"Linux Memory Management List" <linux-mm@kvack.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [External] Re: [PATCH v20 8/9] mm: memory_hotplug: disable memmap_on_memory when hugetlb_free_vmemmap enabled
Date: Wed, 21 Apr 2021 11:41:24 +0800
Message-ID: <CAMZfGtXmDhkCWateAR0q_EgRPDmGh_=D-6UuhMd+Si6=TDvghQ@mail.gmail.com> (raw)
In-Reply-To: <YH6udU5rKmDcx5dY@localhost.localdomain>

On Tue, Apr 20, 2021 at 6:35 PM Oscar Salvador <osalvador@suse.de> wrote:
>
> On Thu, Apr 15, 2021 at 04:40:04PM +0800, Muchun Song wrote:
> >  bool mhp_supports_memmap_on_memory(unsigned long size)
> >  {
> > +     bool supported;
> >       unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
> >       unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
> >       unsigned long remaining_size = size - vmemmap_size;
> > @@ -1011,11 +1012,18 @@ bool mhp_supports_memmap_on_memory(unsigned long size)
> >        *       altmap as an alternative source of memory, and we do not exactly
> >        *       populate a single PMD.
> >        */
> > -     return memmap_on_memory &&
> > -            IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
> > -            size == memory_block_size_bytes() &&
> > -            IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
> > -            IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT);
> > +     supported = memmap_on_memory &&
> > +                 IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
> > +                 size == memory_block_size_bytes() &&
> > +                 IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
> > +                 IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT);
> > +
> > +     if (supported && is_hugetlb_free_vmemmap_enabled()) {
> > +             pr_info("Cannot enable memory_hotplug.memmap_on_memory, it is not compatible with hugetlb_free_vmemmap\n");
> > +             supported = false;
> > +     }
>
> I would not print anything and rather have
>
> return memmap_on_memory &&
>        !is_hugetlb_free_vmemmap_enabled &&
>        IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
>        size == memory_block_size_bytes() &&
>        IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
>        IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT);

OK. Will do.

>
> Documentation/admin-guide/kernel-parameters.txt already provides an
> explanation on memory_hotplug.memmap_on_memory parameter that states
> that the feature cannot be enabled when using hugetlb-vmemmap
> optimization.
>
> Users can always check whether the feature is enabled via
> /sys/modules/memory_hotplug/parameters/memmap_on_memory.

If memory_hotplug.memmap_on_memory is enabled

    $ cat /sys/module/memory_hotplug/parameters/memmap_on_memory
    $ Y

If memory_hotplug.memmap_on_memory is disabled

    $ cat /sys/module/memory_hotplug/parameters/memmap_on_memory
    $ N

>
> Also, I did not check if it is, but if not, the fact about hugetlb-vmemmmap vs
> hotplug-vmemmap should also be called out in the hugetlb-vmemmap kernel
> parameter.

Make sense. I will update the doc.

Thanks.

>
> Thanks
>
> --
> Oscar Salvador
> SUSE L3

  reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-15  8:39 [PATCH v20 0/9] Free some vmemmap pages of HugeTLB page Muchun Song
2021-04-15  8:39 ` [PATCH v20 1/9] mm: memory_hotplug: factor out bootmem core functions to bootmem_info.c Muchun Song
2021-04-15  8:39 ` [PATCH v20 2/9] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2021-04-15  8:39 ` [PATCH v20 3/9] mm: hugetlb: gather discrete indexes of tail page Muchun Song
2021-04-16 18:54   ` Mike Kravetz
2021-04-15  8:40 ` [PATCH v20 4/9] mm: hugetlb: free the vmemmap pages associated with each HugeTLB page Muchun Song
2021-04-16 21:10   ` Mike Kravetz
2021-04-17  2:55     ` [External] " Muchun Song
2021-04-15  8:40 ` [PATCH v20 5/9] mm: hugetlb: defer freeing of HugeTLB pages Muchun Song
2021-04-16 23:55   ` Mike Kravetz
2021-04-17  4:13     ` [External] " Muchun Song
2021-04-15  8:40 ` [PATCH v20 6/9] mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page Muchun Song
2021-04-19 23:19   ` Mike Kravetz
2021-04-20  8:46     ` [External] " Muchun Song
2021-04-20 17:48       ` Mike Kravetz
2021-04-21  3:42         ` Muchun Song
2021-04-15  8:40 ` [PATCH v20 7/9] mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap Muchun Song
2021-04-19 23:41   ` Mike Kravetz
2021-04-15  8:40 ` [PATCH v20 8/9] mm: memory_hotplug: disable memmap_on_memory when hugetlb_free_vmemmap enabled Muchun Song
2021-04-20 10:35   ` Oscar Salvador
2021-04-21  3:41     ` Muchun Song [this message]
2021-04-21  7:33       ` [External] " Oscar Salvador
2021-04-21  9:06         ` Muchun Song
2021-04-15  8:40 ` [PATCH v20 9/9] mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate Muchun Song

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