From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: Nitesh Narayan Lal <nitesh@redhat.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: Mon, 16 Dec 2019 08:10:11 -0800 [thread overview]
Message-ID: <0a7a6e978960fd6d02a7ba2584d72e58fe1b3a05.camel@linux.intel.com> (raw)
In-Reply-To: <34abf700-bdb0-e01b-c7c2-3eab8d058c22@redhat.com>
On Mon, 2019-12-16 at 06:44 -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.
> >
> > 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?
My thought is to wait until we are actually processing the request. That
way we are only performing this check once every 2 seconds instead of
every time we are thinking about requesting page reporting.
Keep in mind I removed the reported_pages tracking statistics so we now
are requesting as soon as we free any page. So if we moved the check tot
he request itself it would mean that a low memory condition would result
in us repeatedly checking the low water mark and failing the test.
next prev parent reply other threads:[~2019-12-16 16:34 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
2019-12-16 16:10 ` Alexander Duyck [this message]
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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