linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: David Hildenbrand <david@redhat.com>
To: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	virtio-dev@lists.oasis-open.org, kvm list <kvm@vger.kernel.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Dave Hansen <dave.hansen@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	linux-mm <linux-mm@kvack.org>, Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	linux-arm-kernel@lists.infradead.org,
	Oscar Salvador <osalvador@suse.de>,
	Yang Zhang <yang.zhang.wz@gmail.com>,
	Pankaj Gupta <pagupta@redhat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Nitesh Narayan Lal <nitesh@redhat.com>,
	Rik van Riel <riel@surriel.com>,
	lcapitulino@redhat.com, "Wang, Wei W" <wei.w.wang@intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Alexander Duyck <alexander.h.duyck@linux.intel.com>
Subject: Re: [PATCH v10 0/6] mm / virtio: Provide support for unused page reporting
Date: Tue, 24 Sep 2019 19:28:19 +0200	[thread overview]
Message-ID: <2fc579f6-9096-4162-9980-1f7f22c5f4ae@redhat.com> (raw)
In-Reply-To: <CAKgT0UedoNBk3cp64SpCzXJqjtqBWZQSB7QzF7R_jhTDXbzNPg@mail.gmail.com>

On 24.09.19 19:07, Alexander Duyck wrote:
> On Tue, Sep 24, 2019 at 8:32 AM David Hildenbrand <david@redhat.com> wrote:
>>
>> On 24.09.19 16:23, Michal Hocko wrote:
>>> On Wed 18-09-19 10:52:25, Alexander Duyck wrote:
>>> [...]
>>>> In order to try and keep the time needed to find a non-reported page to
>>>> a minimum we maintain a "reported_boundary" pointer. This pointer is used
>>>> by the get_unreported_pages iterator to determine at what point it should
>>>> resume searching for non-reported pages. In order to guarantee pages do
>>>> not get past the scan I have modified add_to_free_list_tail so that it
>>>> will not insert pages behind the reported_boundary.
>>>>
>>>> If another process needs to perform a massive manipulation of the free
>>>> list, such as compaction, it can either reset a given individual boundary
>>>> which will push the boundary back to the list_head, or it can clear the
>>>> bit indicating the zone is actively processing which will result in the
>>>> reporting process resetting all of the boundaries for a given zone.
>>>
>>> Is this any different from the previous version? The last review
>>> feedback (both from me and Mel) was that we are not happy to have an
>>> externally imposed constrains on how the page allocator is supposed to
>>> maintain its free lists.
>>>
>>> If this is really the only way to go forward then I would like to hear
>>> very convincing arguments about other approaches not being feasible.
>>
>> Adding to what Alexander said, I don't consider the other approaches
>> (especially the bitmap-based approach Nitesh is currently working on)
>> infeasible. There might be more rough edges (e.g., sparse zones) and
>> eventually sometimes a little more work to be done, but definitely
>> feasible. Incorporating stuff into the buddy might make some tasks
>> (e.g., identify free pages) more efficient.
>>
>> I still somewhat like the idea of capturing hints of free pages (in
>> whatever data structure) and then going over the hints, seeing if the
>> pages are still free. Then only temporarily isolating the still-free
>> pages, reporting them, and un-isolating them after they were reported. I
>> like the idea that the pages are not fake-allocated but only temporarily
>> blocked. That works nicely e.g., with the movable zone (contain only
>> movable data).
> 
> One other change in this patch set is that I split the headers so that
> there is an internal header that resides in the mm tree and an
> external one that provides the page reporting device structure and the
> register/unregister functions. All that virtio-balloon knows is that
> it is registering a notifier and will be called with scatter gather
> lists for memory that is not currently in use by the kernel. It has no
> visibility into the internal free_areas or the current state of the
> buddy allocator. Rather than having two blocks that are both trying to
> maintain that state, I have consolidated it all into the buddy
> allocator with page reporting.
> 
>> But anyhow, after decades of people working on free page
>> hinting/reporting, I am happy with anything that gets accepted upstream :D
> 
> Agreed. After working on this for 9 months I would be happy to get
> something upstream that addresses this.

IBM upstreamed their proprietary solution - 45e576b1c3d0 ("S390] guest
page hinting light") - in 2008.

Rik has presented a generic approach in 2011 (!)
https://www.linux-kvm.org/images/f/ff/2011-forum-memory-overcommit.pdf

I think Nitesh has been working on this (initially as an Intern) since
Mid 2017.

So yeah, this stuff has quite some history :)

> 
> - Alex
> 


-- 

Thanks,

David / dhildenb

      reply	other threads:[~2019-09-24 17:28 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-18 17:52 Alexander Duyck
2019-09-18 17:52 ` [PATCH v10 1/6] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2019-09-18 17:52 ` [PATCH v10 2/6] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2019-09-18 17:52 ` [PATCH v10 3/6] mm: Introduce Reported pages Alexander Duyck
2019-09-21 15:25   ` [mm] 0f5b256b2c: will-it-scale.per_process_ops -1.2% regression kernel test robot
2019-09-23  8:15   ` [PATCH v10 3/6] mm: Introduce Reported pages Michael S. Tsirkin
2019-09-23 14:50     ` Alexander Duyck
2019-09-23 15:00       ` Michael S. Tsirkin
2019-09-23 15:28         ` Alexander Duyck
2019-09-23 15:37           ` Michael S. Tsirkin
2019-09-23 15:45             ` David Hildenbrand
2019-09-23 15:47               ` David Hildenbrand
2019-09-23 15:50                 ` Michael S. Tsirkin
2019-09-23 15:53                   ` David Hildenbrand
2019-09-23 15:49               ` Michael S. Tsirkin
2019-09-23 16:39               ` Alexander Duyck
2019-09-18 17:52 ` [PATCH v10 4/6] mm: Add device side and notifier for unused page reporting Alexander Duyck
2019-09-18 17:53 ` [PATCH v10 5/6] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2019-09-18 17:58   ` Michael S. Tsirkin
2019-09-18 18:05     ` Alexander Duyck
2019-09-18 17:53 ` [PATCH v10 6/6] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck
2019-09-18 17:53 ` [PATCH v10 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck
2019-09-18 17:53 ` [PATCH v10 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck
2019-09-18 17:53 ` [PATCH v10 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck
2019-09-24 14:23 ` [PATCH v10 0/6] mm / virtio: Provide support " Michal Hocko
2019-09-24 15:20   ` Alexander Duyck
2019-09-26 12:22     ` Michal Hocko
2019-09-26 15:13       ` Alexander Duyck
2019-09-24 15:32   ` David Hildenbrand
2019-09-24 15:51     ` Nitesh Narayan Lal
2019-09-24 17:07     ` Alexander Duyck
2019-09-24 17:28       ` David Hildenbrand [this message]

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=2fc579f6-9096-4162-9980-1f7f22c5f4ae@redhat.com \
    --to=david@redhat.com \
    --cc=aarcange@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=alexander.duyck@gmail.com \
    --cc=alexander.h.duyck@linux.intel.com \
    --cc=dan.j.williams@intel.com \
    --cc=dave.hansen@intel.com \
    --cc=konrad.wilk@oracle.com \
    --cc=kvm@vger.kernel.org \
    --cc=lcapitulino@redhat.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mgorman@techsingularity.net \
    --cc=mhocko@kernel.org \
    --cc=mst@redhat.com \
    --cc=nitesh@redhat.com \
    --cc=osalvador@suse.de \
    --cc=pagupta@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=riel@surriel.com \
    --cc=vbabka@suse.cz \
    --cc=virtio-dev@lists.oasis-open.org \
    --cc=wei.w.wang@intel.com \
    --cc=willy@infradead.org \
    --cc=yang.zhang.wz@gmail.com \
    --subject='Re: [PATCH v10 0/6] mm / virtio: Provide support for unused page reporting' \
    /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

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).