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From: David Hildenbrand <david@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, nitesh@redhat.com,
	konrad.wilk@oracle.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 3/7] mm: Add function __putback_isolated_page
Date: Mon, 16 Dec 2019 12:36:14 +0100	[thread overview]
Message-ID: <cb49bbc7-b0c0-65cc-1d9d-a3aaef075650@redhat.com> (raw)
In-Reply-To: <20191205162230.19548.70198.stgit@localhost.localdomain>

[...]
> +/**
> + * __putback_isolated_page - Return a now-isolated page back where we got it
> + * @page: Page that was isolated
> + * @order: Order of the isolated page
> + *
> + * This function is meant to return a page pulled from the free lists via
> + * __isolate_free_page back to the free lists they were pulled from.
> + */
> +void __putback_isolated_page(struct page *page, unsigned int order)
> +{
> +	struct zone *zone = page_zone(page);
> +	unsigned long pfn;
> +	unsigned int mt;
> +
> +	/* zone lock should be held when this function is called */
> +	lockdep_assert_held(&zone->lock);
> +
> +	pfn = page_to_pfn(page);
> +	mt = get_pfnblock_migratetype(page, pfn);

IMHO get_pageblock_migratetype() would be nicer - I guess the compiler
will optimize out the double page_to_pfn().

> +
> +	/* Return isolated page to tail of freelist. */
> +	__free_one_page(page, pfn, zone, order, mt);
> +}
> +
>  /*
>   * Update NUMA hit/miss statistics
>   *
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 04ee1663cdbe..d93d2be0070f 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -134,13 +134,11 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
>  		__mod_zone_freepage_state(zone, nr_pages, migratetype);
>  	}
>  	set_pageblock_migratetype(page, migratetype);
> +	if (isolated_page)
> +		__putback_isolated_page(page, order);
>  	zone->nr_isolate_pageblock--;
>  out:
>  	spin_unlock_irqrestore(&zone->lock, flags);
> -	if (isolated_page) {
> -		post_alloc_hook(page, order, __GFP_MOVABLE);
> -		__free_pages(page, order);
> -	}

So If I get it right:

post_alloc_hook() does quite some stuff like
- arch_alloc_page(page, order);
- kernel_map_pages(page, 1 << order, 1)
- kasan_alloc_pages()
- kernel_poison_pages(1)
- set_page_owner()

Which free_pages_prepare() will undo, like
- reset_page_owner()
- kernel_poison_pages(0)
- arch_free_page()
- kernel_map_pages()
- kasan_free_nondeferred_pages()

Both would be skipped now - which sounds like the right thing to do IMHO
(and smells like quite a performance improvement). I haven't verified if
actually everything we skip in free_pages_prepare() is safe (I think it
is, it seems to be mostly relevant for actually used/allocated pages).

-- 
Thanks,

David / dhildenb


  reply	other threads:[~2019-12-16 11:36 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 [this message]
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
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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