From: Nitesh Narayan Lal <nitesh@redhat.com>
To: Alexander Duyck <alexander.duyck@gmail.com>
Cc: kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
virtio-dev@lists.oasis-open.org,
Paolo Bonzini <pbonzini@redhat.com>,
lcapitulino@redhat.com, Pankaj Gupta <pagupta@redhat.com>,
"Wang, Wei W" <wei.w.wang@intel.com>,
Yang Zhang <yang.zhang.wz@gmail.com>,
Rik van Riel <riel@surriel.com>,
David Hildenbrand <david@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
dodgen@google.com, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
dhildenb@redhat.com, Andrea Arcangeli <aarcange@redhat.com>,
john.starks@microsoft.com, Dave Hansen <dave.hansen@intel.com>,
Michal Hocko <mhocko@suse.com>,
cohuck@redhat.com
Subject: Re: [RFC][Patch v12 1/2] mm: page_reporting: core infrastructure
Date: Fri, 11 Oct 2019 07:02:56 -0400 [thread overview]
Message-ID: <be33c1fe-ce15-aaef-3f15-617fc5b792f4@redhat.com> (raw)
In-Reply-To: <CAKgT0UeKxCYtg6+aCPyxJcAGrBgvCWziUpZM6Tmw-9PSChcGVA@mail.gmail.com>
On 10/10/19 4:36 PM, Alexander Duyck wrote:
> On Mon, Aug 12, 2019 at 6:13 AM Nitesh Narayan Lal <nitesh@redhat.com> wrote:
> <snip>
>
>> +static int process_free_page(struct page *page,
>> + struct page_reporting_config *phconf, int count)
>> +{
>> + int mt, order, ret = 0;
>> +
>> + mt = get_pageblock_migratetype(page);
>> + order = page_private(page);
>> + ret = __isolate_free_page(page, order);
>> +
>> + if (ret) {
>> + /*
>> + * Preserving order and migratetype for reuse while
>> + * releasing the pages back to the buddy.
>> + */
>> + set_pageblock_migratetype(page, mt);
>> + set_page_private(page, order);
>> +
>> + sg_set_page(&phconf->sg[count++], page,
>> + PAGE_SIZE << order, 0);
>> + }
>> +
>> + return count;
>> +}
>> +
>> +/**
>> + * scan_zone_bitmap - scans the bitmap for the requested zone.
>> + * @phconf: page reporting configuration object initialized by the backend.
>> + * @zone: zone for which page reporting is requested.
>> + *
>> + * For every page marked in the bitmap it checks if it is still free if so it
>> + * isolates and adds them to a scatterlist. As soon as the number of isolated
>> + * pages reach the threshold set by the backend, they are reported to the
>> + * hypervisor by the backend. Once the hypervisor responds after processing
>> + * they are returned back to the buddy for reuse.
>> + */
>> +static void scan_zone_bitmap(struct page_reporting_config *phconf,
>> + struct zone *zone)
>> +{
>> + unsigned long setbit;
>> + struct page *page;
>> + int count = 0;
>> +
>> + sg_init_table(phconf->sg, phconf->max_pages);
>> +
>> + for_each_set_bit(setbit, zone->bitmap, zone->nbits) {
>> + /* Process only if the page is still online */
>> + page = pfn_to_online_page((setbit << PAGE_REPORTING_MIN_ORDER) +
>> + zone->base_pfn);
>> + if (!page)
>> + continue;
>> +
>> + spin_lock(&zone->lock);
>> +
>> + /* Ensure page is still free and can be processed */
>> + if (PageBuddy(page) && page_private(page) >=
>> + PAGE_REPORTING_MIN_ORDER)
>> + count = process_free_page(page, phconf, count);
>> +
>> + spin_unlock(&zone->lock);
>> + /* Page has been processed, adjust its bit and zone counter */
>> + clear_bit(setbit, zone->bitmap);
>> + atomic_dec(&zone->free_pages);
>> +
>> + if (count == phconf->max_pages) {
>> + /* Report isolated pages to the hypervisor */
>> + phconf->report(phconf, count);
>> +
>> + /* Return processed pages back to the buddy */
>> + return_isolated_page(zone, phconf);
>> +
>> + /* Reset for next reporting */
>> + sg_init_table(phconf->sg, phconf->max_pages);
>> + count = 0;
>> + }
>> + }
>> + /*
>> + * If the number of isolated pages does not meet the max_pages
>> + * threshold, we would still prefer to report them as we have already
>> + * isolated them.
>> + */
>> + if (count) {
>> + sg_mark_end(&phconf->sg[count - 1]);
>> + phconf->report(phconf, count);
>> +
>> + return_isolated_page(zone, phconf);
>> + }
>> +}
>> +
> So one thing that occurred to me is that this code is missing checks
> so that it doesn't try to hint isolated pages. With the bitmap
> approach you need an additional check so that you aren't pulling
> isolated pages out and reporting them.
I think you mean that we should not report pages of type MIGRATE_ISOLATE.
The current code on which I am working, I have added the
is_migrate_isolate_page() check
to ensure that I am not processing these pages.
--
Thanks
Nitesh
next prev parent reply other threads:[~2019-10-11 11:03 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-12 13:12 [RFC][PATCH v12 0/2] mm: Support for page reporting Nitesh Narayan Lal
2019-08-12 13:12 ` [RFC][Patch v12 1/2] mm: page_reporting: core infrastructure Nitesh Narayan Lal
2019-08-12 18:47 ` Alexander Duyck
2019-08-12 20:04 ` Nitesh Narayan Lal
2019-08-20 14:11 ` Nitesh Narayan Lal
2019-08-12 20:05 ` David Hildenbrand
2019-08-13 10:30 ` Nitesh Narayan Lal
2019-08-13 10:34 ` David Hildenbrand
2019-08-13 10:42 ` Nitesh Narayan Lal
2019-08-13 10:44 ` David Hildenbrand
2019-08-13 23:14 ` Alexander Duyck
2019-08-14 7:07 ` David Hildenbrand
2019-08-14 12:49 ` [virtio-dev] " Nitesh Narayan Lal
2019-08-14 15:49 ` Nitesh Narayan Lal
2019-08-14 16:11 ` Alexander Duyck
2019-08-15 13:15 ` Nitesh Narayan Lal
2019-08-15 19:22 ` Nitesh Narayan Lal
2019-08-15 23:00 ` Alexander Duyck
2019-08-16 18:35 ` Nitesh Narayan Lal
2019-08-30 15:15 ` Nitesh Narayan Lal
2019-08-30 15:31 ` Alexander Duyck
2019-08-30 16:05 ` Nitesh Narayan Lal
2019-09-04 8:40 ` [virtio-dev] " David Hildenbrand
2019-10-10 20:36 ` Alexander Duyck
2019-10-11 11:02 ` Nitesh Narayan Lal [this message]
2019-08-12 13:12 ` [RFC][Patch v12 2/2] virtio-balloon: interface to support free page reporting Nitesh Narayan Lal
2019-08-14 10:29 ` Cornelia Huck
2019-08-14 11:47 ` Nitesh Narayan Lal
2019-08-14 13:42 ` Cornelia Huck
2019-08-14 14:01 ` Nitesh Narayan Lal
2019-08-12 13:13 ` [QEMU Patch 1/2] virtio-balloon: adding bit for page reporting support Nitesh Narayan Lal
2019-08-12 13:13 ` [QEMU Patch 2/2] virtio-balloon: support for handling page reporting Nitesh Narayan Lal
2019-08-12 15:18 ` Alexander Duyck
2019-08-12 15:26 ` Nitesh Narayan Lal
2019-09-11 12:30 ` [RFC][PATCH v12 0/2] mm: Support for " David Hildenbrand
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