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From: Nitesh Narayan Lal <nitesh@redhat.com>
To: David Hildenbrand <david@redhat.com>,
	Michal Hocko <mhocko@kernel.org>,
	Alexander Duyck <alexander.duyck@gmail.com>
Cc: virtio-dev@lists.oasis-open.org, kvm@vger.kernel.org,
	mst@redhat.com, dave.hansen@intel.com,
	linux-kernel@vger.kernel.org, willy@infradead.org,
	linux-mm@kvack.org, vbabka@suse.cz, akpm@linux-foundation.org,
	mgorman@techsingularity.net,
	linux-arm-kernel@lists.infradead.org, osalvador@suse.de,
	yang.zhang.wz@gmail.com, pagupta@redhat.com,
	konrad.wilk@oracle.com, riel@surriel.com, lcapitulino@redhat.com,
	wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com,
	dan.j.williams@intel.com, 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 11:51:42 -0400	[thread overview]
Message-ID: <fc288e95-2203-2db8-1f34-a1bbcfa1f24d@redhat.com> (raw)
In-Reply-To: <d2a7acdd-3bb9-05c9-42d0-70a500801cd6@redhat.com>


On 9/24/19 11:32 AM, David Hildenbrand 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.

My plan was to get a framework ready which can perform decently and
is acceptable upstream (keeping core-mm changes to a minimum) and then keep
optimizing it for different use-cases.
Indeed, the bitmap-based approach may not be efficient for every available use
case. But then I am not sure if we want to target that, considering it may require
mm-changes.

> 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).
>
> But anyhow, after decades of people working on free page
> hinting/reporting, I am happy with anything that gets accepted upstream :D

+1

>
-- 
Nitesh


  reply	other threads:[~2019-09-24 15:52 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 [this message]
2019-09-24 17:07     ` Alexander Duyck
2019-09-24 17:28       ` David Hildenbrand

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