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SubjectRe: [PATCH v8] mm/page_alloc.c: memory_hotplug: free pages as higher order
On 2019-01-09 21:47, Alexander Duyck wrote:
> On Wed, 2019-01-09 at 16:43 +0530, Arun KS wrote:
>> When freeing pages are done with higher order, time spent on
>> coalescing
>> pages by buddy allocator can be reduced. With section size of 256MB,
>> hot
>> add latency of a single section shows improvement from 50-60 ms to
>> less
>> than 1 ms, hence improving the hot add latency by 60 times. Modify
>> external providers of online callback to align with the change.
>>
>> Signed-off-by: Arun KS <arunks@codeaurora.org>
>> Acked-by: Michal Hocko <mhocko@suse.com>
>> Reviewed-by: Oscar Salvador <osalvador@suse.de>
>> ---
>> Changes since v7:
>> - Rebased to 5.0-rc1.
>> - Fixed onlined_pages accounting.
>> - Added comment for return value of online_page_callback.
>> - Renamed xen_bring_pgs_online to xen_online_pages.
>
> As far as the renaming you should try to be consistent. If you aren't
> going to rename generic_online_page or hv_online_page I wouldn't bother
> with renaming xen_online_page. I would stick with the name
> xen_online_page since it is a single high order page that you are
> freeing.

Sure. I ll fix them.

>
>>
>> Changes since v6:
>> - Rebased to 4.20
>> - Changelog updated.
>> - No improvement seen on arm64, hence removed removal of prefetch.
>>
>> Changes since v5:
>> - Rebased to 4.20-rc1.
>> - Changelog updated.
>>
>> Changes since v4:
>> - As suggested by Michal Hocko,
>> - Simplify logic in online_pages_block() by using get_order().
>> - Seperate out removal of prefetch from __free_pages_core().
>>
>> Changes since v3:
>> - Renamed _free_pages_boot_core -> __free_pages_core.
>> - Removed prefetch from __free_pages_core.
>> - Removed xen_online_page().
>>
>> Changes since v2:
>> - Reuse code from __free_pages_boot_core().
>>
>> Changes since v1:
>> - Removed prefetch().
>>
>> Changes since RFC:
>> - Rebase.
>> - As suggested by Michal Hocko remove pages_per_block.
>> - Modifed external providers of online_page_callback.
>>
>> v7: https://lore.kernel.org/patchwork/patch/1028908/
>> v6: https://lore.kernel.org/patchwork/patch/1007253/
>> v5: https://lore.kernel.org/patchwork/patch/995739/
>> v4: https://lore.kernel.org/patchwork/patch/995111/
>> v3: https://lore.kernel.org/patchwork/patch/992348/
>> v2: https://lore.kernel.org/patchwork/patch/991363/
>> v1: https://lore.kernel.org/patchwork/patch/989445/
>> RFC: https://lore.kernel.org/patchwork/patch/984754/
>> ---
>> drivers/hv/hv_balloon.c | 6 +++--
>> drivers/xen/balloon.c | 21 +++++++++++------
>> include/linux/memory_hotplug.h | 2 +-
>> mm/internal.h | 1 +
>> mm/memory_hotplug.c | 51
>> +++++++++++++++++++++++++++++++-----------
>> mm/page_alloc.c | 8 +++----
>> 6 files changed, 62 insertions(+), 27 deletions(-)
>>
>> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
>> index 5301fef..211f3fe 100644
>> --- a/drivers/hv/hv_balloon.c
>> +++ b/drivers/hv/hv_balloon.c
>> @@ -771,7 +771,7 @@ static void hv_mem_hot_add(unsigned long start,
>> unsigned long size,
>> }
>> }
>>
>> -static void hv_online_page(struct page *pg)
>> +static int hv_online_page(struct page *pg, unsigned int order)
>> {
>> struct hv_hotadd_state *has;
>> unsigned long flags;
>> @@ -783,10 +783,12 @@ static void hv_online_page(struct page *pg)
>> if ((pfn < has->start_pfn) || (pfn >= has->end_pfn))
>> continue;
>>
>> - hv_page_online_one(has, pg);
>> + hv_bring_pgs_online(has, pfn, (1UL << order));
>> break;
>> }
>> spin_unlock_irqrestore(&dm_device.ha_lock, flags);
>> +
>> + return 0;
>> }
>>
>
> I would hold off on adding return values until you actually have code
> that uses them. It will make things easier if somebody has to backport
> this to a stable branch and avoid adding complexity until it is needed.
>
> Also the patch description doesn't really explain that it is doing this
> so it might be better to break it off into a separate patch so you can
> call out exactly why you are adding a return value in the patch
> description.
>
> - Alex

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