From: Vlastimil Babka <vbabka@suse.cz>
To: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Rik van Riel <riel@redhat.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Mel Gorman <mgorman@suse.de>, Hugh Dickins <hughd@google.com>,
Rafael Aquini <aquini@redhat.com>,
virtualization@lists.linux-foundation.org,
Jonathan Corbet <corbet@lwn.net>,
John Einar Reitan <john.reitan@foss.arm.com>,
dri-devel@lists.freedesktop.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Gioh Kim <gi-oh.kim@profitbricks.com>
Subject: Re: PATCH v6v2 02/12] mm: migrate: support non-lru movable page migration
Date: Mon, 30 May 2016 11:36:07 +0200 [thread overview]
Message-ID: <2bc277c4-4257-c6cb-2e37-ee5de985410b@suse.cz> (raw)
In-Reply-To: <20160530013926.GB8683@bbox>
On 05/30/2016 03:39 AM, Minchan Kim wrote:
> After isolation, VM calls migratepage of driver with isolated page.
> The function of migratepage is to move content of the old page to new page
> and set up fields of struct page newpage. Keep in mind that you should
> clear PG_movable of oldpage via __ClearPageMovable under page_lock if you
> migrated the oldpage successfully and returns 0.
This "clear PG_movable" is one of the reasons I was confused about what
__ClearPageMovable() really does. There's no actual "PG_movable" page
flag and the function doesn't clear even the actual mapping flag :) Also
same thing in the Documentation/ part.
Something like "... you should indicate to the VM that the oldpage is no
longer movable via __ClearPageMovable() ..."?
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -81,6 +81,39 @@ static inline bool migrate_async_suitable(int migratetype)
>
> #ifdef CONFIG_COMPACTION
>
> +int PageMovable(struct page *page)
> +{
> + struct address_space *mapping;
> +
> + VM_BUG_ON_PAGE(!PageLocked(page), page);
> + if (!__PageMovable(page))
> + return 0;
> +
> + mapping = page_mapping(page);
> + if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
> + return 1;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(PageMovable);
> +
> +void __SetPageMovable(struct page *page, struct address_space *mapping)
> +{
> + VM_BUG_ON_PAGE(!PageLocked(page), page);
> + VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
> + page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
> +}
> +EXPORT_SYMBOL(__SetPageMovable);
> +
> +void __ClearPageMovable(struct page *page)
> +{
> + VM_BUG_ON_PAGE(!PageLocked(page), page);
> + VM_BUG_ON_PAGE(!PageMovable(page), page);
> + page->mapping = (void *)((unsigned long)page->mapping &
> + PAGE_MAPPING_MOVABLE);
> +}
> +EXPORT_SYMBOL(__ClearPageMovable);
The second confusing thing is that the function is named
__ClearPageMovable(), but what it really clears is the mapping pointer,
which is not at all the opposite of what __SetPageMovable() does.
I know it's explained in the documentation, but it also deserves a
comment here so it doesn't confuse everyone who looks at it.
Even better would be a less confusing name for the function, but I can't
offer one right now.
> diff --git a/mm/util.c b/mm/util.c
> index 917e0e3d0f8e..b756ee36f7f0 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -399,10 +399,12 @@ struct address_space *page_mapping(struct page *page)
> }
>
> mapping = page->mapping;
I'd probably use READ_ONCE() here to be safe. Not all callers are under
page lock?
> - if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
> + if ((unsigned long)mapping & PAGE_MAPPING_ANON)
> return NULL;
> - return mapping;
> +
> + return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
> }
> +EXPORT_SYMBOL(page_mapping);
>
> /* Slow path of page_mapcount() for compound pages */
> int __page_mapcount(struct page *page)
>
next prev parent reply other threads:[~2016-05-30 9:36 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-20 14:23 [PATCH v6 00/12] Support non-lru page migration Minchan Kim
2016-05-20 14:23 ` [PATCH v6 01/12] mm: use put_page to free page instead of putback_lru_page Minchan Kim
2016-05-20 14:23 ` [PATCH v6 02/12] mm: migrate: support non-lru movable page migration Minchan Kim
2016-05-27 14:26 ` Vlastimil Babka
2016-05-30 1:33 ` Minchan Kim
2016-05-30 9:01 ` Vlastimil Babka
2016-05-30 1:39 ` PATCH v6v2 " Minchan Kim
2016-05-30 9:36 ` Vlastimil Babka [this message]
2016-05-30 16:25 ` Minchan Kim
2016-05-31 7:51 ` Vlastimil Babka
2016-05-31 0:01 ` [PATCH v6v3 " Minchan Kim
2016-05-31 7:52 ` Vlastimil Babka
2016-05-31 23:05 ` Minchan Kim
2016-06-13 9:38 ` Anshuman Khandual
2016-06-15 2:32 ` Minchan Kim
2016-06-15 6:45 ` Anshuman Khandual
2016-06-16 0:26 ` Minchan Kim
2016-06-16 3:42 ` Anshuman Khandual
2016-06-16 5:37 ` Minchan Kim
2016-06-27 5:51 ` Anshuman Khandual
2016-06-28 6:39 ` Minchan Kim
2016-06-30 5:56 ` Anshuman Khandual
2016-06-30 6:18 ` Minchan Kim
2016-05-20 14:23 ` [PATCH v6 03/12] mm: balloon: use general non-lru movable page feature Minchan Kim
2016-05-30 12:16 ` Vlastimil Babka
2016-05-20 14:23 ` [PATCH v6 04/12] zsmalloc: keep max_object in size_class Minchan Kim
2016-05-20 14:23 ` [PATCH v6 05/12] zsmalloc: use bit_spin_lock Minchan Kim
2016-05-20 14:23 ` [PATCH v6 06/12] zsmalloc: use accessor Minchan Kim
2016-05-20 14:23 ` [PATCH v6 07/12] zsmalloc: factor page chain functionality out Minchan Kim
2016-05-20 14:23 ` [PATCH v6 08/12] zsmalloc: introduce zspage structure Minchan Kim
2016-05-20 14:23 ` [PATCH v6 09/12] zsmalloc: separate free_zspage from putback_zspage Minchan Kim
2016-05-20 14:23 ` [PATCH v6 10/12] zsmalloc: use freeobj for index Minchan Kim
2016-05-20 14:23 ` [PATCH v6 11/12] zsmalloc: page migration support Minchan Kim
2016-05-24 5:28 ` Sergey Senozhatsky
2016-05-24 6:28 ` Minchan Kim
2016-05-24 8:05 ` Sergey Senozhatsky
2016-05-24 8:17 ` Minchan Kim
2016-05-25 5:14 ` Minchan Kim
2016-05-25 15:23 ` Sergey Senozhatsky
2016-05-26 0:32 ` Minchan Kim
2016-05-26 0:59 ` Sergey Senozhatsky
2016-05-26 4:37 ` Minchan Kim
2016-05-26 21:50 ` [PATCH v6r2 " Minchan Kim
2016-05-20 14:23 ` [PATCH v6 12/12] zram: use __GFP_MOVABLE for memory allocation Minchan Kim
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