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Groups > linux.kernel > #1702714 > unrolled thread

[PATCH v13 0/5] Virtio-balloon Enhancement

Started byWei Wang <wei.w.wang@intel.com>
First post2017-08-03 08:50 +0200
Last post2017-08-10 10:00 +0200
Articles 6 on this page of 26 — 4 participants

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  [PATCH v13 0/5] Virtio-balloon Enhancement Wei Wang <wei.w.wang@intel.com> - 2017-08-03 08:50 +0200
    [PATCH v13 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG Wei Wang <wei.w.wang@intel.com> - 2017-08-03 09:00 +0200
      Re: [PATCH v13 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG "Michael S. Tsirkin" <mst@redhat.com> - 2017-08-03 16:30 +0200
        RE: [PATCH v13 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG "Wang, Wei W" <wei.w.wang@intel.com> - 2017-08-03 17:20 +0200
          Re: [PATCH v13 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG "Michael S. Tsirkin" <mst@redhat.com> - 2017-08-03 18:00 +0200
    [PATCH v13 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-03 09:00 +0200
      Re: [PATCH v13 4/5] mm: support reporting free page blocks Michal Hocko <mhocko@kernel.org> - 2017-08-03 11:20 +0200
        Re: [PATCH v13 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-03 12:40 +0200
          Re: [PATCH v13 4/5] mm: support reporting free page blocks Michal Hocko <mhocko@kernel.org> - 2017-08-03 12:50 +0200
            Re: [PATCH v13 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-03 13:30 +0200
              Re: [PATCH v13 4/5] mm: support reporting free page blocks Michal Hocko <mhocko@kernel.org> - 2017-08-03 13:30 +0200
                Re: [PATCH v13 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-03 14:10 +0200
                  Re: [PATCH v13 4/5] mm: support reporting free page blocks Michal Hocko <mhocko@kernel.org> - 2017-08-03 14:50 +0200
                    Re: [PATCH v13 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-03 15:20 +0200
                      Re: [PATCH v13 4/5] mm: support reporting free page blocks Michal Hocko <mhocko@kernel.org> - 2017-08-03 16:00 +0200
                        RE: [PATCH v13 4/5] mm: support reporting free page blocks "Wang, Wei W" <wei.w.wang@intel.com> - 2017-08-03 17:30 +0200
                          Re: [PATCH v13 4/5] mm: support reporting free page blocks "Michael S. Tsirkin" <mst@redhat.com> - 2017-08-03 23:10 +0200
                            Re: [PATCH v13 4/5] mm: support reporting free page blocks Michal Hocko <mhocko@kernel.org> - 2017-08-04 10:00 +0200
                              Re: [PATCH v13 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-04 10:20 +0200
                                Re: [PATCH v13 4/5] mm: support reporting free page blocks Michal Hocko <mhocko@kernel.org> - 2017-08-04 10:30 +0200
                                  Re: [PATCH v13 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-04 11:00 +0200
        Re: [PATCH v13 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-08 08:20 +0200
          Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page  blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-08 08:40 +0200
            Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page  blocks Michal Hocko <mhocko@kernel.org> - 2017-08-10 09:10 +0200
              Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page  blocks Wei Wang <wei.w.wang@intel.com> - 2017-08-10 09:40 +0200
                Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page  blocks Michal Hocko <mhocko@kernel.org> - 2017-08-10 10:00 +0200

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#1703800 — Re: [PATCH v13 4/5] mm: support reporting free page blocks

FromWei Wang <wei.w.wang@intel.com>
Date2017-08-04 11:00 +0200
SubjectRe: [PATCH v13 4/5] mm: support reporting free page blocks
Message-ID<uaGCB-4L1-13@gated-at.bofh.it>
In reply to#1703785
On 08/04/2017 04:24 PM, Michal Hocko wrote:
>
>> For our use case, the callback just puts the reported page
>> block to the ring, then returns. If the ring is full as the host
>> is busy, then I think it should skip this one, and just return.
>> Because:
>>      A. This is an optimization feature, losing a couple of free
>>           pages to report isn't that important;
>>      B. In reality, I think it's uncommon to see this ring getting
>>          full (I didn't observe ring full in the tests), since the host
>>          (consumer) is notified to take out the page block right
>>          after it is added.
> I thought you only updated a pre allocated bitmat... Anyway, I cannot
> comment on this part much as I am not familiar with your usecase.
>   

Actually the bitmap is in the hypervisor (host). The callback puts the
(pfn,size) on a ring which is shared with the hypervisor, then the
hypervisor takes that info from the ring and updates that bitmap.


Best,
Wei

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#1706052 — Re: [PATCH v13 4/5] mm: support reporting free page blocks

FromWei Wang <wei.w.wang@intel.com>
Date2017-08-08 08:20 +0200
SubjectRe: [PATCH v13 4/5] mm: support reporting free page blocks
Message-ID<uc61X-3Rd-1@gated-at.bofh.it>
In reply to#1702820
On 08/03/2017 05:11 PM, Michal Hocko wrote:
> On Thu 03-08-17 14:38:18, Wei Wang wrote:
> This is just too ugly and wrong actually. Never provide struct page
> pointers outside of the zone->lock. What I've had in mind was to simply
> walk free lists of the suitable order and call the callback for each one.
> Something as simple as
>
> 	for (i = 0; i < MAX_NR_ZONES; i++) {
> 		struct zone *zone = &pgdat->node_zones[i];
>
> 		if (!populated_zone(zone))
> 			continue;

Can we directly use for_each_populated_zone(zone) here?


> 		spin_lock_irqsave(&zone->lock, flags);
> 		for (order = min_order; order < MAX_ORDER; ++order) {


This appears to be covered by for_each_migratetype_order(order, mt) below.


> 			struct free_area *free_area = &zone->free_area[order];
> 			enum migratetype mt;
> 			struct page *page;
>
> 			if (!free_area->nr_pages)
> 				continue;
>
> 			for_each_migratetype_order(order, mt) {
> 				list_for_each_entry(page,
> 						&free_area->free_list[mt], lru) {
>
> 					pfn = page_to_pfn(page);
> 					visit(opaque2, prn, 1<<order);
> 				}
> 			}
> 		}
>
> 		spin_unlock_irqrestore(&zone->lock, flags);
> 	}
>
> [...]
>

What do you think if we further simply the above implementation like this:

for_each_populated_zone(zone) {
                 for_each_migratetype_order_decend(1, order, mt) {
                         spin_lock_irqsave(&zone->lock, flags);
                         list_for_each_entry(page,
&zone->free_area[order].free_list[mt], lru) {
                                 pfn = page_to_pfn(page);
                                 visit(opaque1, pfn, 1 << order);
                         }
                         spin_unlock_irqrestore(&zone->lock, flags);
                 }
         }


Best,
Wei

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#1706066 — Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks

FromWei Wang <wei.w.wang@intel.com>
Date2017-08-08 08:40 +0200
SubjectRe: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks
Message-ID<uc6lj-3ZY-15@gated-at.bofh.it>
In reply to#1706052
On 08/08/2017 02:12 PM, Wei Wang wrote:
> On 08/03/2017 05:11 PM, Michal Hocko wrote:
>> On Thu 03-08-17 14:38:18, Wei Wang wrote:
>> This is just too ugly and wrong actually. Never provide struct page
>> pointers outside of the zone->lock. What I've had in mind was to simply
>> walk free lists of the suitable order and call the callback for each 
>> one.
>> Something as simple as
>>
>>     for (i = 0; i < MAX_NR_ZONES; i++) {
>>         struct zone *zone = &pgdat->node_zones[i];
>>
>>         if (!populated_zone(zone))
>>             continue;
>
> Can we directly use for_each_populated_zone(zone) here?
>
>
>> spin_lock_irqsave(&zone->lock, flags);
>>         for (order = min_order; order < MAX_ORDER; ++order) {
>
>
> This appears to be covered by for_each_migratetype_order(order, mt) 
> below.
>
>
>>             struct free_area *free_area = &zone->free_area[order];
>>             enum migratetype mt;
>>             struct page *page;
>>
>>             if (!free_area->nr_pages)
>>                 continue;
>>
>>             for_each_migratetype_order(order, mt) {
>>                 list_for_each_entry(page,
>>                         &free_area->free_list[mt], lru) {
>>
>>                     pfn = page_to_pfn(page);
>>                     visit(opaque2, prn, 1<<order);
>>                 }
>>             }
>>         }
>>
>>         spin_unlock_irqrestore(&zone->lock, flags);
>>     }
>>
>> [...]
>>
>
> What do you think if we further simply the above implementation like 
> this:
>
> for_each_populated_zone(zone) {
>                 for_each_migratetype_order_decend(1, order, mt) {

here it will be min_order (passed by the caller), instead of "1",
that is, for_each_migratetype_order_decend(min_order, order, mt)


> spin_lock_irqsave(&zone->lock, flags);
>                         list_for_each_entry(page,
> &zone->free_area[order].free_list[mt], lru) {
>                                 pfn = page_to_pfn(page);
>                                 visit(opaque1, pfn, 1 << order);
>                         }
>                         spin_unlock_irqrestore(&zone->lock, flags);
>                 }
>         }
>
>


Best,
Wei

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#1708265 — Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks

FromMichal Hocko <mhocko@kernel.org>
Date2017-08-10 09:10 +0200
SubjectRe: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks
Message-ID<ucPLs-2cT-17@gated-at.bofh.it>
In reply to#1706066
On Tue 08-08-17 14:34:25, Wei Wang wrote:
> On 08/08/2017 02:12 PM, Wei Wang wrote:
> >On 08/03/2017 05:11 PM, Michal Hocko wrote:
> >>On Thu 03-08-17 14:38:18, Wei Wang wrote:
> >>This is just too ugly and wrong actually. Never provide struct page
> >>pointers outside of the zone->lock. What I've had in mind was to simply
> >>walk free lists of the suitable order and call the callback for each
> >>one.
> >>Something as simple as
> >>
> >>    for (i = 0; i < MAX_NR_ZONES; i++) {
> >>        struct zone *zone = &pgdat->node_zones[i];
> >>
> >>        if (!populated_zone(zone))
> >>            continue;
> >
> >Can we directly use for_each_populated_zone(zone) here?

yes, my example couldn't because I was still assuming per-node API

> >>spin_lock_irqsave(&zone->lock, flags);
> >>        for (order = min_order; order < MAX_ORDER; ++order) {
> >
> >
> >This appears to be covered by for_each_migratetype_order(order, mt) below.

yes but
#define for_each_migratetype_order(order, type) \
	for (order = 0; order < MAX_ORDER; order++) \
		for (type = 0; type < MIGRATE_TYPES; type++)

so you would have to skip orders < min_order
-- 
Michal Hocko
SUSE Labs

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#1708283 — Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks

FromWei Wang <wei.w.wang@intel.com>
Date2017-08-10 09:40 +0200
SubjectRe: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks
Message-ID<ucQeu-2mz-17@gated-at.bofh.it>
In reply to#1708265
On 08/10/2017 03:05 PM, Michal Hocko wrote:
> On Tue 08-08-17 14:34:25, Wei Wang wrote:
>> On 08/08/2017 02:12 PM, Wei Wang wrote:
>>> On 08/03/2017 05:11 PM, Michal Hocko wrote:
>>>> On Thu 03-08-17 14:38:18, Wei Wang wrote:
>>>> This is just too ugly and wrong actually. Never provide struct page
>>>> pointers outside of the zone->lock. What I've had in mind was to simply
>>>> walk free lists of the suitable order and call the callback for each
>>>> one.
>>>> Something as simple as
>>>>
>>>>     for (i = 0; i < MAX_NR_ZONES; i++) {
>>>>         struct zone *zone = &pgdat->node_zones[i];
>>>>
>>>>         if (!populated_zone(zone))
>>>>             continue;
>>> Can we directly use for_each_populated_zone(zone) here?
> yes, my example couldn't because I was still assuming per-node API
>
>>>> spin_lock_irqsave(&zone->lock, flags);
>>>>         for (order = min_order; order < MAX_ORDER; ++order) {
>>>
>>> This appears to be covered by for_each_migratetype_order(order, mt) below.
> yes but
> #define for_each_migratetype_order(order, type) \
> 	for (order = 0; order < MAX_ORDER; order++) \
> 		for (type = 0; type < MIGRATE_TYPES; type++)
>
> so you would have to skip orders < min_order

Yes, that's why we have a new macro

#define for_each_migratetype_order_decend(min_order, order, type) \
  for (order = MAX_ORDER - 1; order < MAX_ORDER && order >= min_order; \
  order--) \
     for (type = 0; type < MIGRATE_TYPES; type++)

If you don't like the macro, we can also directly use it in the code.

I think it would be better to report the larger free page block first, since
the callback has an opportunity (though just a theoretical possibility, 
good to
take that into consideration if possible) to skip reporting the given 
free page
block to the hypervisor as the ring gets full. Losing the small block is 
better
than losing the larger one, in terms of the optimization work.


Best,
Wei

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#1708291 — Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks

FromMichal Hocko <mhocko@kernel.org>
Date2017-08-10 10:00 +0200
SubjectRe: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks
Message-ID<ucQxP-2tn-5@gated-at.bofh.it>
In reply to#1708283
On Thu 10-08-17 15:38:34, Wei Wang wrote:
> On 08/10/2017 03:05 PM, Michal Hocko wrote:
> >On Tue 08-08-17 14:34:25, Wei Wang wrote:
> >>On 08/08/2017 02:12 PM, Wei Wang wrote:
> >>>On 08/03/2017 05:11 PM, Michal Hocko wrote:
> >>>>On Thu 03-08-17 14:38:18, Wei Wang wrote:
> >>>>This is just too ugly and wrong actually. Never provide struct page
> >>>>pointers outside of the zone->lock. What I've had in mind was to simply
> >>>>walk free lists of the suitable order and call the callback for each
> >>>>one.
> >>>>Something as simple as
> >>>>
> >>>>    for (i = 0; i < MAX_NR_ZONES; i++) {
> >>>>        struct zone *zone = &pgdat->node_zones[i];
> >>>>
> >>>>        if (!populated_zone(zone))
> >>>>            continue;
> >>>Can we directly use for_each_populated_zone(zone) here?
> >yes, my example couldn't because I was still assuming per-node API
> >
> >>>>spin_lock_irqsave(&zone->lock, flags);
> >>>>        for (order = min_order; order < MAX_ORDER; ++order) {
> >>>
> >>>This appears to be covered by for_each_migratetype_order(order, mt) below.
> >yes but
> >#define for_each_migratetype_order(order, type) \
> >	for (order = 0; order < MAX_ORDER; order++) \
> >		for (type = 0; type < MIGRATE_TYPES; type++)
> >
> >so you would have to skip orders < min_order
> 
> Yes, that's why we have a new macro
> 
> #define for_each_migratetype_order_decend(min_order, order, type) \
>  for (order = MAX_ORDER - 1; order < MAX_ORDER && order >= min_order; \
>  order--) \
>     for (type = 0; type < MIGRATE_TYPES; type++)
> 
> If you don't like the macro, we can also directly use it in the code.
> 
> I think it would be better to report the larger free page block first, since
> the callback has an opportunity (though just a theoretical possibility, good
> to
> take that into consideration if possible) to skip reporting the given free
> page
> block to the hypervisor as the ring gets full. Losing the small block is
> better
> than losing the larger one, in terms of the optimization work.

I see. But I think this is so specialized that opencoding the macro
would be easier to read.

-- 
Michal Hocko
SUSE Labs

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