linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Muchun Song <songmuchun@bytedance.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
	dave.hansen@linux.intel.com, luto@kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	viro@zeniv.linux.org.uk,
	Andrew Morton <akpm@linux-foundation.org>,
	paulmck@kernel.org, mchehab+huawei@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>,
	Oscar Salvador <osalvador@suse.de>,
	"Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
	Xiongchun duan <duanxiongchun@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 v5 00/21] Free some vmemmap pages of hugetlb page
Date: Fri, 20 Nov 2020 23:44:26 +0800	[thread overview]
Message-ID: <CAMZfGtWNDJWWTtpUDtngtgNiOoSd6sJpdAB6MnJW8KH0gePfYA@mail.gmail.com> (raw)
In-Reply-To: <20201120131129.GO3200@dhcp22.suse.cz>

On Fri, Nov 20, 2020 at 9:11 PM Michal Hocko <mhocko@suse.com> wrote:
>
> On Fri 20-11-20 20:40:46, Muchun Song wrote:
> > On Fri, Nov 20, 2020 at 4:42 PM Michal Hocko <mhocko@suse.com> wrote:
> > >
> > > On Fri 20-11-20 14:43:04, Muchun Song wrote:
> > > [...]
> > >
> > > Thanks for improving the cover letter and providing some numbers. I have
> > > only glanced through the patchset because I didn't really have more time
> > > to dive depply into them.
> > >
> > > Overall it looks promissing. To summarize. I would prefer to not have
> > > the feature enablement controlled by compile time option and the kernel
> > > command line option should be opt-in. I also do not like that freeing
> > > the pool can trigger the oom killer or even shut the system down if no
> > > oom victim is eligible.
> >
> > Hi Michal,
> >
> > I have replied to you about those questions on the other mail thread.
> >
> > Thanks.
> >
> > >
> > > One thing that I didn't really get to think hard about is what is the
> > > effect of vmemmap manipulation wrt pfn walkers. pfn_to_page can be
> > > invalid when racing with the split. How do we enforce that this won't
> > > blow up?
> >
> > This feature depends on the CONFIG_SPARSEMEM_VMEMMAP,
> > in this case, the pfn_to_page can work. The return value of the
> > pfn_to_page is actually the address of it's struct page struct.
> > I can not figure out where the problem is. Can you describe the
> > problem in detail please? Thanks.
>
> struct page returned by pfn_to_page might get invalid right when it is
> returned because vmemmap could get freed up and the respective memory
> released to the page allocator and reused for something else. See?

If the HugeTLB page is already allocated from the buddy allocator,
the struct page of the HugeTLB can be freed? Does this exist?
If yes, how to free the HugeTLB page to the buddy allocator
(cannot access the struct page)?

>
> > > I have also asked in a previous version whether the vmemmap manipulation
> > > should be really unconditional. E.g. shortlived hugetlb pages allocated
> > > from the buddy allocator directly rather than for a pool. Maybe it
> > > should be restricted for the pool allocation as those are considered
> > > long term and therefore the overhead will be amortized and freeing path
> > > restrictions better understandable.
> >
> > Yeah, I agree with you. This can be an optimization. And we can
> > add it to the todo list and implement it in the future. Now the patch
> > series is already huge.
>
> Yes the patchset is large and the primary aim should be reducing
> functionality to make it smaller in the first incarnation. Especially
> when it is tricky to implement. Releasing vmemmap sparse hugepages is
> one of those things. Do you really need it for your usecase?
> --
> Michal Hocko
> SUSE Labs



-- 
Yours,
Muchun

  reply	other threads:[~2020-11-20 15:45 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-20  6:43 [PATCH v5 00/21] Free some vmemmap pages of hugetlb page Muchun Song
2020-11-20  6:43 ` [PATCH v5 01/21] mm/memory_hotplug: Move bootmem info registration API to bootmem_info.c Muchun Song
2020-11-20  6:43 ` [PATCH v5 02/21] mm/memory_hotplug: Move {get,put}_page_bootmem() " Muchun Song
2020-11-20  6:43 ` [PATCH v5 03/21] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2020-11-20  7:49   ` Michal Hocko
2020-11-20  8:35     ` [External] " Muchun Song
2020-11-20  8:47       ` Michal Hocko
2020-11-20  8:53         ` Muchun Song
2020-11-20  6:43 ` [PATCH v5 04/21] mm/hugetlb: Introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2020-11-20  6:43 ` [PATCH v5 05/21] mm/hugetlb: Introduce pgtable allocation/freeing helpers Muchun Song
2020-11-20  6:43 ` [PATCH v5 06/21] mm/bootmem_info: Introduce {free,prepare}_vmemmap_page() Muchun Song
2020-11-20  6:43 ` [PATCH v5 07/21] mm/bootmem_info: Combine bootmem info and type into page->freelist Muchun Song
2020-11-20  6:43 ` [PATCH v5 08/21] mm/hugetlb: Initialize page table lock for vmemmap Muchun Song
2020-11-20  6:43 ` [PATCH v5 09/21] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page Muchun Song
2020-11-20  6:43 ` [PATCH v5 10/21] mm/hugetlb: Defer freeing of hugetlb pages Muchun Song
2020-11-20  6:43 ` [PATCH v5 11/21] mm/hugetlb: Allocate the vmemmap pages associated with each hugetlb page Muchun Song
2020-11-20  8:11   ` Michal Hocko
2020-11-20  8:51     ` [External] " Muchun Song
2020-11-20  9:28       ` Michal Hocko
2020-11-20  9:37         ` Muchun Song
2020-11-20 11:10           ` Michal Hocko
2020-11-20 11:56             ` Muchun Song
2020-11-20  6:43 ` [PATCH v5 12/21] mm/hugetlb: Introduce remap_huge_page_pmd_vmemmap helper Muchun Song
2020-11-20  6:43 ` [PATCH v5 13/21] mm/hugetlb: Use PG_slab to indicate split pmd Muchun Song
2020-11-20  8:16   ` Michal Hocko
2020-11-20  9:30     ` [External] " Muchun Song
2020-11-23  7:48       ` Michal Hocko
2020-11-23  8:01         ` Muchun Song
2020-11-20  6:43 ` [PATCH v5 14/21] mm/hugetlb: Support freeing vmemmap pages of gigantic page Muchun Song
2020-11-20  6:43 ` [PATCH v5 15/21] mm/hugetlb: Set the PageHWPoison to the raw error page Muchun Song
2020-11-20  8:19   ` Michal Hocko
2020-11-20 10:32     ` [External] " Muchun Song
2020-11-20  6:43 ` [PATCH v5 16/21] mm/hugetlb: Flush work when dissolving hugetlb page Muchun Song
2020-11-20  8:20   ` Michal Hocko
2020-11-20  6:43 ` [PATCH v5 17/21] mm/hugetlb: Add a kernel parameter hugetlb_free_vmemmap Muchun Song
2020-11-20  8:22   ` Michal Hocko
2020-11-20 10:39     ` [External] " Muchun Song
2020-11-20  6:43 ` [PATCH v5 18/21] mm/hugetlb: Merge pte to huge pmd only for gigantic page Muchun Song
2020-11-20  8:23   ` Michal Hocko
2020-11-20 10:41     ` [External] " Muchun Song
2020-11-20  6:43 ` [PATCH v5 19/21] mm/hugetlb: Gather discrete indexes of tail page Muchun Song
2020-11-20  6:43 ` [PATCH v5 20/21] mm/hugetlb: Add BUILD_BUG_ON to catch invalid usage of tail struct page Muchun Song
2020-11-20  6:43 ` [PATCH v5 21/21] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two Muchun Song
2020-11-20  8:25   ` Michal Hocko
2020-11-20  9:15     ` David Hildenbrand
2020-11-22 13:30       ` Mike Rapoport
2020-11-22 19:00     ` Matthew Wilcox
2020-11-23  3:14       ` [External] " Muchun Song
2020-11-20  9:16   ` David Hildenbrand
2020-11-20 10:42     ` [External] " Muchun Song
2020-11-20  8:42 ` [PATCH v5 00/21] Free some vmemmap pages of hugetlb page Michal Hocko
2020-11-20  9:27   ` David Hildenbrand
2020-11-20  9:39     ` Michal Hocko
2020-11-20  9:43       ` David Hildenbrand
2020-11-20 17:45         ` Mike Kravetz
2020-11-20 18:00           ` David Hildenbrand
2020-11-22  7:29           ` [External] " Muchun Song
2020-11-23  7:38           ` Michal Hocko
2020-11-23 21:52             ` Mike Kravetz
2020-11-23 22:01               ` Matthew Wilcox
2020-11-20 12:40   ` [External] " Muchun Song
2020-11-20 13:11     ` Michal Hocko
2020-11-20 15:44       ` Muchun Song [this message]
2020-11-23  7:40         ` Michal Hocko
2020-11-23  8:53           ` Muchun Song
2020-11-23  9:43             ` Michal Hocko
2020-11-23 10:36               ` Muchun Song
2020-11-23 10:42                 ` Michal Hocko
2020-11-23 11:16                   ` Muchun Song
2020-11-23 11:32                     ` Michal Hocko
2020-11-23 12:07                       ` Muchun Song
2020-11-23 12:18                         ` Michal Hocko
2020-11-23 12:40                           ` Muchun Song
2020-11-23 12:48                             ` Michal Hocko
2020-11-23 12:45                   ` Matthew Wilcox
2020-11-23 13:05                     ` Muchun Song
2020-11-23 13:13                     ` Michal Hocko

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAMZfGtWNDJWWTtpUDtngtgNiOoSd6sJpdAB6MnJW8KH0gePfYA@mail.gmail.com \
    --to=songmuchun@bytedance.com \
    --cc=akpm@linux-foundation.org \
    --cc=almasrymina@google.com \
    --cc=anshuman.khandual@arm.com \
    --cc=bp@alien8.de \
    --cc=corbet@lwn.net \
    --cc=dave.hansen@linux.intel.com \
    --cc=duanxiongchun@bytedance.com \
    --cc=hpa@zytor.com \
    --cc=jroedel@suse.de \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=luto@kernel.org \
    --cc=mchehab+huawei@kernel.org \
    --cc=mhocko@suse.com \
    --cc=mike.kravetz@oracle.com \
    --cc=mingo@redhat.com \
    --cc=oneukum@suse.com \
    --cc=osalvador@suse.de \
    --cc=paulmck@kernel.org \
    --cc=pawan.kumar.gupta@linux.intel.com \
    --cc=peterz@infradead.org \
    --cc=rdunlap@infradead.org \
    --cc=rientjes@google.com \
    --cc=song.bao.hua@hisilicon.com \
    --cc=tglx@linutronix.de \
    --cc=viro@zeniv.linux.org.uk \
    --cc=willy@infradead.org \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).