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From: Nitesh Narayan Lal <nitesh@redhat.com>
To: 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, alexander.h.duyck@linux.intel.com,
	osalvador@suse.de
Subject: Re: [PATCH v15 4/7] mm: Introduce Reported pages
Date: Mon, 16 Dec 2019 06:44:37 -0500	[thread overview]
Message-ID: <34abf700-bdb0-e01b-c7c2-3eab8d058c22@redhat.com> (raw)
In-Reply-To: <20191205162238.19548.68238.stgit@localhost.localdomain>


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.
>
> To prevent the reported pages from leaking outside of the buddy lists I
> added a check to clear the PageReported bit in the del_page_from_free_list
> function. As a result any reported page that is split, merged, or
> allocated will have the flag cleared prior to the PageBuddy value being
> cleared.
>
> The process for reporting pages is fairly simple. Once we free a page that
> meets the minimum order for page reporting we will schedule a worker thread
> to start 2s or more in the future. That worker thread will begin working
> from the lowest supported page reporting order up to MAX_ORDER - 1 pulling
> unreported pages from the free list and storing them in the scatterlist.
>
> When processing each individual free list it is necessary for the worker
> thread to release the zone lock when it needs to stop and report the full
> scatterlist of pages. To reduce the work of the next iteration the worker
> thread will rotate the free list so that the first unreported page in the
> free list becomes the first entry in the list.

[...]

> k);
> +
> +	return err;
> +}
> +
> +static int
> +page_reporting_process_zone(struct page_reporting_dev_info *prdev,
> +			    struct scatterlist *sgl, struct zone *zone)
> +{
> +	unsigned int order, mt, leftover, offset = PAGE_REPORTING_CAPACITY;
> +	unsigned long watermark;
> +	int err = 0;
> +
> +	/* Generate minimum watermark to be able to guarantee progress */
> +	watermark = low_wmark_pages(zone) +
> +		    (PAGE_REPORTING_CAPACITY << PAGE_REPORTING_MIN_ORDER);
> +
> +	/*
> +	 * Cancel request if insufficient free memory or if we failed
> +	 * to allocate page reporting statistics for the zone.
> +	 */
> +	if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
> +		return err;
> +


Will it not make more sense to check the low watermark condition before every
reporting request generated for a bunch of 32 isolated pages?
or will that be too costly?

> +	/* Process each free list starting from lowest order/mt */
> +	for (order = PAGE_REPORTING_MIN_ORDER; order < MAX_ORDER; order++) {
> +		for (mt = 0; mt < MIGRATE_TYPES; mt++) {
> +			/* We do not pull pages from the isolate free list */
> +			if (is_migrate_isolate(mt))
> +				continue;
> +
> +			err = page_reporting_cycle(prdev, zone, order, mt,
> +						   sgl, &offset);
> +			if (err)
> +				return err;
> +		}
> +	}
> +
> +	/* report the leftover pages before going idle */
> +	leftover = PAGE_REPORTING_CAPACITY - offset;
> +	if (leftover) {
> +		sgl = &sgl[offset];
> +		err = prdev->report(prdev, sgl, leftover);
> +
> +		/* flush any remaining pages out from the last report */
> +		spin_lock_irq(&zone->lock);
> +		page_reporting_drain(prdev, sgl, leftover, !err);
> +		spin_unlock_irq(&zone->lock);
> +	}
> +
> +	return err;
> +}
-- 
Nitesh


  parent reply	other threads:[~2019-12-16 11:45 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
2019-12-17 16:31         ` Alexander Duyck
2019-12-18  7:31           ` Mel Gorman
2019-12-16 11:44   ` Nitesh Narayan Lal [this message]
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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