From: Minchan Kim <minchan@kernel.org>
To: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>, Rik van Riel <riel@redhat.com>,
Vlastimil Babka <vbabka@suse.cz>,
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 v6v3 02/12] mm: migrate: support non-lru movable page migration
Date: Thu, 16 Jun 2016 09:26:17 +0900 [thread overview]
Message-ID: <20160616002617.GM17127@bbox> (raw)
In-Reply-To: <5760F970.7060805@linux.vnet.ibm.com>
On Wed, Jun 15, 2016 at 12:15:04PM +0530, Anshuman Khandual wrote:
> On 06/15/2016 08:02 AM, Minchan Kim wrote:
> > Hi,
> >
> > On Mon, Jun 13, 2016 at 03:08:19PM +0530, Anshuman Khandual wrote:
> >> > On 05/31/2016 05:31 AM, Minchan Kim wrote:
> >>> > > @@ -791,6 +921,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
> >>> > > int rc = -EAGAIN;
> >>> > > int page_was_mapped = 0;
> >>> > > struct anon_vma *anon_vma = NULL;
> >>> > > + bool is_lru = !__PageMovable(page);
> >>> > >
> >>> > > if (!trylock_page(page)) {
> >>> > > if (!force || mode == MIGRATE_ASYNC)
> >>> > > @@ -871,6 +1002,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
> >>> > > goto out_unlock_both;
> >>> > > }
> >>> > >
> >>> > > + if (unlikely(!is_lru)) {
> >>> > > + rc = move_to_new_page(newpage, page, mode);
> >>> > > + goto out_unlock_both;
> >>> > > + }
> >>> > > +
> >> >
> >> > Hello Minchan,
> >> >
> >> > I might be missing something here but does this implementation support the
> >> > scenario where these non LRU pages owned by the driver mapped as PTE into
> >> > process page table ? Because the "goto out_unlock_both" statement above
> >> > skips all the PTE unmap, putting a migration PTE and removing the migration
> >> > PTE steps.
> > You're right. Unfortunately, it doesn't support right now but surely,
> > it's my TODO after landing this work.
> >
> > Could you share your usecase?
>
> Sure.
Thanks a lot!
>
> My driver has privately managed non LRU pages which gets mapped into user space
> process page table through f_ops->mmap() and vmops->fault() which then updates
> the file RMAP (page->mapping->i_mmap) through page_add_file_rmap(page). One thing
Hmm, page_add_file_rmap is not exported function. How does your driver can use it?
Do you use vm_insert_pfn?
What type your vma is? VM_PFNMMAP or VM_MIXEDMAP?
I want to make dummy driver to simulate your case.
It would be very helpful to implement/test pte-mapped non-lru page
migration feature. That's why I ask now.
> to note here is that the page->mapping eventually points to struct address_space
> (file->f_mapping) which belongs to the character device file (created using mknod)
> which we are using for establishing the mmap() regions in the user space.
>
> Now as per this new framework, all the page's are to be made __SetPageMovable before
> passing the list down to migrate_pages(). Now __SetPageMovable() takes *new* struct
> address_space as an argument and replaces the existing page->mapping. Now thats the
> problem, we have lost all our connection to the existing file RMAP information. This
We could change __SetPageMovable doesn't need mapping argument.
Instead, it just marks PAGE_MAPPING_MOVABLE into page->mapping.
For that, user should take care of setting page->mapping earlier than
marking the flag.
> stands as a problem when we try to migrate these non LRU pages which are PTE mapped.
> The rmap_walk_file() never finds them in the VMA, skips all the migrate PTE steps and
> then the migration eventually fails.
>
> Seems like assigning a new struct address_space to the page through __SetPageMovable()
> is the source of the problem. Can it take the existing (file->f_mapping) as an argument
We can set existing file->f_mapping under the page_lock.
> in there ? Sure, but then can we override file system generic ->isolate(), ->putback(),
I don't get it. Why does it override file system generic functions?
> ->migratepages() functions ? I dont think so. I am sure, there must be some work around
> to fix this problem for the driver. But we need to rethink this framework from supporting
> these mapped non LRU pages point of view.
>
> I might be missing something here, feel free to point out.
>
> - Anshuman
>
next prev parent reply other threads:[~2016-06-16 0:26 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
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 [this message]
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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