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From: Nitesh Narayan Lal <nitesh@redhat.com>
To: Alexander Duyck <alexander.h.duyck@linux.intel.com>,
	Alexander Duyck <alexander.duyck@gmail.com>,
	kvm@vger.kernel.org, mst@redhat.com,
	linux-kernel@vger.kernel.org, willy@infradead.org,
	mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org,
	mgorman@techsingularity.net, vbabka@suse.cz
Cc: yang.zhang.wz@gmail.com, konrad.wilk@oracle.com,
	david@redhat.com, pagupta@redhat.com, riel@surriel.com,
	lcapitulino@redhat.com, dave.hansen@intel.com,
	wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com,
	dan.j.williams@intel.com, osalvador@suse.de
Subject: Re: [PATCH v15 4/7] mm: Introduce Reported pages
Date: Tue, 17 Dec 2019 03:55:49 -0500	[thread overview]
Message-ID: <06ca452e-90b3-c1b5-f2c0-e8da2444bcfe@redhat.com> (raw)
In-Reply-To: <537e970f062e0c7f89723f63fc1f3ec6e53614a5.camel@linux.intel.com>


On 12/16/19 11:28 AM, Alexander Duyck wrote:
> On Mon, 2019-12-16 at 05:17 -0500, Nitesh Narayan Lal wrote:
>> On 12/5/19 11:22 AM, Alexander Duyck wrote:
>>> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
>>>
>>> In order to pave the way for free page reporting in virtualized
>>> environments we will need a way to get pages out of the free lists and
>>> identify those pages after they have been returned. To accomplish this,
>>> this patch adds the concept of a Reported Buddy, which is essentially
>>> meant to just be the Uptodate flag used in conjunction with the Buddy
>>> page type.
>> [...]
>>
>>> +enum {
>>> +	PAGE_REPORTING_IDLE = 0,
>>> +	PAGE_REPORTING_REQUESTED,
>>> +	PAGE_REPORTING_ACTIVE
>>> +};
>>> +
>>> +/* request page reporting */
>>> +static void
>>> +__page_reporting_request(struct page_reporting_dev_info *prdev)
>>> +{
>>> +	unsigned int state;
>>> +
>>> +	/* Check to see if we are in desired state */
>>> +	state = atomic_read(&prdev->state);
>>> +	if (state == PAGE_REPORTING_REQUESTED)
>>> +		return;
>>> +
>>> +	/*
>>> +	 *  If reporting is already active there is nothing we need to do.
>>> +	 *  Test against 0 as that represents PAGE_REPORTING_IDLE.
>>> +	 */
>>> +	state = atomic_xchg(&prdev->state, PAGE_REPORTING_REQUESTED);
>>> +	if (state != PAGE_REPORTING_IDLE)
>>> +		return;
>>> +
>>> +	/*
>>> +	 * Delay the start of work to allow a sizable queue to build. For
>>> +	 * now we are limiting this to running no more than once every
>>> +	 * couple of seconds.
>>> +	 */
>>> +	schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY);
>>> +}
>>> +
>> I think you recently switched to using an atomic variable for maintaining page
>> reporting status as I was doing in v12.
>> Which is good, as we will not have a disagreement on it now.
> There is still some differences between our approaches if I am not
> mistaken. Specifically I have code in place so that any requests to report
> while we are actively working on reporting will trigger another pass being
> scheduled after we completed. I still believe you were lacking any logic
> like that as I recall.
>

Yes, I was specifically referring to the atomic state variable.
Though I am wondering if having an atomic variable to track page reporting state
is better than having a page reporting specific unsigned long flag, which we can
manipulate via __set_bit() and __clear_bit().

>> On a side note, apologies for not getting involved actively in the
>> discussions/reviews as I am on PTO.
> No problem. I've been mostly looking for input from the core MM
> maintainers anyway as we sorted most of the virtualization pieces some
> time ago.
>
-- 
Thanks
Nitesh


  reply	other threads:[~2019-12-17  8:56 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-05 16:22 [PATCH v15 0/7] mm / virtio: Provide support for free page reporting Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 1/7] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 2/7] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 3/7] mm: Add function __putback_isolated_page Alexander Duyck
2019-12-16 11:36   ` David Hildenbrand
2019-12-16 16:22     ` Alexander Duyck
2019-12-17 10:58       ` David Hildenbrand
2019-12-17 16:26         ` Alexander Duyck
2019-12-17 17:24           ` David Hildenbrand
2019-12-17 18:24             ` Alexander Duyck
2019-12-17 18:46               ` David Hildenbrand
2019-12-17 21:50                 ` Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 4/7] mm: Introduce Reported pages Alexander Duyck
2019-12-16 10:17   ` Nitesh Narayan Lal
2019-12-16 16:28     ` Alexander Duyck
2019-12-17  8:55       ` Nitesh Narayan Lal [this message]
2019-12-17 16:31         ` Alexander Duyck
2019-12-18  7:31           ` Mel Gorman
2019-12-16 11:44   ` Nitesh Narayan Lal
2019-12-16 16:10     ` Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 5/7] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2019-12-13  7:03   ` Michael S. Tsirkin
2019-12-05 16:22 ` [PATCH v15 6/7] virtio-balloon: Add support for providing free page reports to host Alexander Duyck
2019-12-13  7:08   ` Michael S. Tsirkin
2019-12-13 16:35     ` Alexander Duyck
2019-12-15  9:29       ` Michael S. Tsirkin
2019-12-13 10:15   ` David Hildenbrand
2019-12-13 16:37     ` Alexander Duyck
2019-12-05 16:23 ` [PATCH v15 7/7] mm: Add free page reporting documentation Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck
2019-12-05 16:26 ` [PATCH v15 QEMU 4/3 RFC] memory: Add support for MADV_FREE as mechanism to lazy discard pages Alexander Duyck
2019-12-12 23:47 ` [PATCH v15 0/7] mm / virtio: Provide support for free page reporting Alexander Duyck
2019-12-13 10:00 ` David Hildenbrand
2019-12-13 11:08   ` Mel Gorman
2019-12-13 16:59     ` Alexander Duyck
2019-12-13 16:46   ` Alexander Duyck
2019-12-16 12:21     ` David Hildenbrand

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