diff mbox series

[v3] mm/migrate_device: Try to handle swapcache pages

Message ID 20230606050149.25699-1-mpenttil@redhat.com
State New
Headers
Series [v3] mm/migrate_device: Try to handle swapcache pages |

Commit Message

Mika Penttilä June 6, 2023, 5:01 a.m. UTC 
  From: Mika Penttilä <mpenttil@redhat.com>

Migrating file pages and swapcache pages into device memory is not supported.
The decision is done based on page_mapping(). For now, swapcache pages are not migrated.

Things can however be improved, for swapcache pages. Try to get rid of the swap cache,
and if successful, go ahead as with other anonymous pages.

Cc: Alistair Popple <apopple@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Mika Penttilä <mpenttil@redhat.com>
---

v3:
  - Adjust comments
  - Add Reviewed-bys

v2:
  - use folio_test_anon() (Huang, Ying)

 mm/migrate_device.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

Comments

David Hildenbrand June 6, 2023, 7:44 a.m. UTC | #1 
On 06.06.23 07:01, mpenttil@redhat.com wrote:
> From: Mika Penttilä <mpenttil@redhat.com>
> 
> Migrating file pages and swapcache pages into device memory is not supported.
> The decision is done based on page_mapping(). For now, swapcache pages are not migrated.
> 
> Things can however be improved, for swapcache pages. Try to get rid of the swap cache,
> and if successful, go ahead as with other anonymous pages.
> 
> Cc: Alistair Popple <apopple@nvidia.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Ralph Campbell <rcampbell@nvidia.com>
> Cc: "Huang, Ying" <ying.huang@intel.com>
> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
> Reviewed-by: Alistair Popple <apopple@nvidia.com>
> Signed-off-by: Mika Penttilä <mpenttil@redhat.com>
> ---
> 
> v3:
>    - Adjust comments
>    - Add Reviewed-bys
> 
> v2:
>    - use folio_test_anon() (Huang, Ying)
> 
>   mm/migrate_device.c | 22 ++++++++++++++++------
>   1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index d30c9de60b0d..f76ebccfe067 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -747,13 +747,23 @@ static void __migrate_device_pages(unsigned long *src_pfns,
>   
>   		if (is_device_private_page(newpage) ||
>   		    is_device_coherent_page(newpage)) {
> -			/*
> -			 * For now only support anonymous memory migrating to
> -			 * device private or coherent memory.
> -			 */
> +
>   			if (mapping) {
> -				src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
> -				continue;
> +				struct folio *folio;
> +
> +				folio = page_folio(page);
> +
> +				/*
> +				 * For now only support anonymous memory migrating to
> +				 * device private or coherent memory.
> +				 *
> +				 * Try to get rid of swap cache if possible.
> +				 *
> +				 */
> +				if (!folio_test_anon(folio) || !folio_free_swap(folio)) {
> +					src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
> +					continue;

I'm pretty sure the folio has to be locked in order to call 
folio_free_swap().
David Hildenbrand June 6, 2023, 7:46 a.m. UTC | #2 
On 06.06.23 09:44, David Hildenbrand wrote:
> On 06.06.23 07:01, mpenttil@redhat.com wrote:
>> From: Mika Penttilä <mpenttil@redhat.com>
>>
>> Migrating file pages and swapcache pages into device memory is not supported.
>> The decision is done based on page_mapping(). For now, swapcache pages are not migrated.
>>
>> Things can however be improved, for swapcache pages. Try to get rid of the swap cache,
>> and if successful, go ahead as with other anonymous pages.
>>
>> Cc: Alistair Popple <apopple@nvidia.com>
>> Cc: John Hubbard <jhubbard@nvidia.com>
>> Cc: Ralph Campbell <rcampbell@nvidia.com>
>> Cc: "Huang, Ying" <ying.huang@intel.com>
>> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
>> Reviewed-by: Alistair Popple <apopple@nvidia.com>
>> Signed-off-by: Mika Penttilä <mpenttil@redhat.com>
>> ---
>>
>> v3:
>>     - Adjust comments
>>     - Add Reviewed-bys
>>
>> v2:
>>     - use folio_test_anon() (Huang, Ying)
>>
>>    mm/migrate_device.c | 22 ++++++++++++++++------
>>    1 file changed, 16 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
>> index d30c9de60b0d..f76ebccfe067 100644
>> --- a/mm/migrate_device.c
>> +++ b/mm/migrate_device.c
>> @@ -747,13 +747,23 @@ static void __migrate_device_pages(unsigned long *src_pfns,
>>    
>>    		if (is_device_private_page(newpage) ||
>>    		    is_device_coherent_page(newpage)) {
>> -			/*
>> -			 * For now only support anonymous memory migrating to
>> -			 * device private or coherent memory.
>> -			 */
>> +
>>    			if (mapping) {
>> -				src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
>> -				continue;
>> +				struct folio *folio;
>> +
>> +				folio = page_folio(page);
>> +
>> +				/*
>> +				 * For now only support anonymous memory migrating to
>> +				 * device private or coherent memory.
>> +				 *
>> +				 * Try to get rid of swap cache if possible.
>> +				 *
>> +				 */
>> +				if (!folio_test_anon(folio) || !folio_free_swap(folio)) {
>> +					src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
>> +					continue;
> 
> I'm pretty sure the folio has to be locked in order to call
> folio_free_swap().
> 

Oh, staring at the bigger context, I assume we locked the folios via 
migrate_device_range(), correct?
Mika Penttilä June 6, 2023, 7:59 a.m. UTC | #3 
Hi,

On 6.6.2023 10.46, David Hildenbrand wrote:
> On 06.06.23 09:44, David Hildenbrand wrote:
>> On 06.06.23 07:01, mpenttil@redhat.com wrote:
>>> From: Mika Penttilä <mpenttil@redhat.com>
>>>
>>> Migrating file pages and swapcache pages into device memory is not 
>>> supported.
>>> The decision is done based on page_mapping(). For now, swapcache 
>>> pages are not migrated.
>>>
>>> Things can however be improved, for swapcache pages. Try to get rid 
>>> of the swap cache,
>>> and if successful, go ahead as with other anonymous pages.
>>>
>>> Cc: Alistair Popple <apopple@nvidia.com>
>>> Cc: John Hubbard <jhubbard@nvidia.com>
>>> Cc: Ralph Campbell <rcampbell@nvidia.com>
>>> Cc: "Huang, Ying" <ying.huang@intel.com>
>>> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
>>> Reviewed-by: Alistair Popple <apopple@nvidia.com>
>>> Signed-off-by: Mika Penttilä <mpenttil@redhat.com>
>>> ---
>>>
>>> v3:
>>>     - Adjust comments
>>>     - Add Reviewed-bys
>>>
>>> v2:
>>>     - use folio_test_anon() (Huang, Ying)
>>>
>>>    mm/migrate_device.c | 22 ++++++++++++++++------
>>>    1 file changed, 16 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
>>> index d30c9de60b0d..f76ebccfe067 100644
>>> --- a/mm/migrate_device.c
>>> +++ b/mm/migrate_device.c
>>> @@ -747,13 +747,23 @@ static void __migrate_device_pages(unsigned 
>>> long *src_pfns,
>>>            if (is_device_private_page(newpage) ||
>>>                is_device_coherent_page(newpage)) {
>>> -            /*
>>> -             * For now only support anonymous memory migrating to
>>> -             * device private or coherent memory.
>>> -             */
>>> +
>>>                if (mapping) {
>>> -                src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
>>> -                continue;
>>> +                struct folio *folio;
>>> +
>>> +                folio = page_folio(page);
>>> +
>>> +                /*
>>> +                 * For now only support anonymous memory migrating to
>>> +                 * device private or coherent memory.
>>> +                 *
>>> +                 * Try to get rid of swap cache if possible.
>>> +                 *
>>> +                 */
>>> +                if (!folio_test_anon(folio) || 
>>> !folio_free_swap(folio)) {
>>> +                    src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
>>> +                    continue;
>>
>> I'm pretty sure the folio has to be locked in order to call
>> folio_free_swap().
>>
> 
> Oh, staring at the bigger context, I assume we locked the folios via 
> migrate_device_range(), correct?
> 

Yes either that, or when migrating via virtual addresses 
migrate_vma_collect_pmd() has trylock_page() and we migrate only pages 
which succeed locking.

--Mika
Christoph Hellwig June 7, 2023, 2:10 p.m. UTC | #4 
On Tue, Jun 06, 2023 at 08:01:49AM +0300, mpenttil@redhat.com wrote:
> From: Mika Penttilä <mpenttil@redhat.com>
> 
> Migrating file pages and swapcache pages into device memory is not supported.
> The decision is done based on page_mapping(). For now, swapcache pages are not migrated.

Please fix the commit log formatting, it should not exceed 7 lines.

>  		if (is_device_private_page(newpage) ||
>  		    is_device_coherent_page(newpage)) {
> -			/*
> -			 * For now only support anonymous memory migrating to
> -			 * device private or coherent memory.
> -			 */
> +
>  			if (mapping) {

Very nitpicky, but this empty line looks odd.  Also isn't the comment
still (mostly) correct given that file backed memory is still not
supported?

> +				/*
> +				 * For now only support anonymous memory migrating to
> +				 * device private or coherent memory.
> +				 *
> +				 * Try to get rid of swap cache if possible.
> +				 *
> +				 */
> +				if (!folio_test_anon(folio) || !folio_free_swap(folio)) {

Please avoid the overly long lines.
Mika Penttilä June 7, 2023, 3:56 p.m. UTC | #5 
Hi,


On 7.6.2023 17.10, Christoph Hellwig wrote:
> On Tue, Jun 06, 2023 at 08:01:49AM +0300, mpenttil@redhat.com wrote:
>> From: Mika Penttilä <mpenttil@redhat.com>
>>
>> Migrating file pages and swapcache pages into device memory is not supported.
>> The decision is done based on page_mapping(). For now, swapcache pages are not migrated.
> 
> Please fix the commit log formatting, it should not exceed 7 lines.
> 
>>   		if (is_device_private_page(newpage) ||
>>   		    is_device_coherent_page(newpage)) {
>> -			/*
>> -			 * For now only support anonymous memory migrating to
>> -			 * device private or coherent memory.
>> -			 */
>> +
>>   			if (mapping) {
> 
> Very nitpicky, but this empty line looks odd.  Also isn't the comment
> still (mostly) correct given that file backed memory is still not
> supported?

Yes the comment is mostly correct and moved a few lines lower, 
complemented with a comment about the swap cache.

> 
>> +				/*
>> +				 * For now only support anonymous memory migrating to
>> +				 * device private or coherent memory.
>> +				 *
>> +				 * Try to get rid of swap cache if possible.
>> +				 *
>> +				 */
>> +				if (!folio_test_anon(folio) || !folio_free_swap(folio)) {
> 
> Please avoid the overly long lines.
> 

Thanks,
Mika
Mika Penttilä June 7, 2023, 4:06 p.m. UTC | #6 
On 7.6.2023 17.10, Christoph Hellwig wrote:
> On Tue, Jun 06, 2023 at 08:01:49AM +0300, mpenttil@redhat.com wrote:
>> From: Mika Penttilä <mpenttil@redhat.com>
>>
>> Migrating file pages and swapcache pages into device memory is not supported.
>> The decision is done based on page_mapping(). For now, swapcache pages are not migrated.
> 
> Please fix the commit log formatting, it should not exceed 7 lines.

Not sure what you mean should not exceed 7 lines..?
Christoph Hellwig June 12, 2023, 4:53 a.m. UTC | #7 
On Wed, Jun 07, 2023 at 07:06:06PM +0300, Mika Penttilä wrote:
> 
> 
> On 7.6.2023 17.10, Christoph Hellwig wrote:
> > On Tue, Jun 06, 2023 at 08:01:49AM +0300, mpenttil@redhat.com wrote:
> > > From: Mika Penttilä <mpenttil@redhat.com>
> > > 
> > > Migrating file pages and swapcache pages into device memory is not supported.
> > > The decision is done based on page_mapping(). For now, swapcache pages are not migrated.
> > 
> > Please fix the commit log formatting, it should not exceed 7 lines.
> 
> Not sure what you mean should not exceed 7 lines..?

Sorry, this should be 73.
diff mbox series

Patch

diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index d30c9de60b0d..f76ebccfe067 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -747,13 +747,23 @@  static void __migrate_device_pages(unsigned long *src_pfns,
 
 		if (is_device_private_page(newpage) ||
 		    is_device_coherent_page(newpage)) {
-			/*
-			 * For now only support anonymous memory migrating to
-			 * device private or coherent memory.
-			 */
+
 			if (mapping) {
-				src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
-				continue;
+				struct folio *folio;
+
+				folio = page_folio(page);
+
+				/*
+				 * For now only support anonymous memory migrating to
+				 * device private or coherent memory.
+				 *
+				 * Try to get rid of swap cache if possible.
+				 *
+				 */
+				if (!folio_test_anon(folio) || !folio_free_swap(folio)) {
+					src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
+					continue;
+				}
 			}
 		} else if (is_zone_device_page(newpage)) {
 			/*