On 22.12.20 09:31, David Hildenbrand wrote:
> On 22.12.20 08:49, Liang Li wrote:
>> This patch add support of pre zero out free hugepage, we can use
>> this feature to speed up page population and page fault handing.
>>
>> Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
>> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
>> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
>> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
>> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
>> Cc: David Hildenbrand <david@xxxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
>> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
>> Cc: Jason Wang <jasowang@xxxxxxxxxx>
>> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>> Cc: Liang Li <liliang324@xxxxxxxxx>
>> Signed-off-by: Liang Li <liliangleo@xxxxxxxxxxxxxx>
>> ---
>> mm/page_prezero.c | 17 +++++++++++++++++
>> 1 file changed, 17 insertions(+)
>>
>> diff --git a/mm/page_prezero.c b/mm/page_prezero.c
>> index c8ce720bfc54..dff4e0adf402 100644
>> --- a/mm/page_prezero.c
>> +++ b/mm/page_prezero.c
>> @@ -26,6 +26,7 @@ static unsigned long delay_millisecs = 1000;
>> static unsigned long zeropage_enable __read_mostly;
>> static DEFINE_MUTEX(kzeropaged_mutex);
>> static struct page_reporting_dev_info zero_page_dev_info;
>> +static struct page_reporting_dev_info zero_hugepage_dev_info;
>>
>> inline void clear_zero_page_flag(struct page *page, int order)
>> {
>> @@ -69,9 +70,17 @@ static int start_kzeropaged(void)
>> zero_page_dev_info.delay_jiffies = msecs_to_jiffies(delay_millisecs);
>>
>> err = page_reporting_register(&zero_page_dev_info);
>> +
>> + zero_hugepage_dev_info.report = zero_free_pages;
>> + zero_hugepage_dev_info.mini_order = mini_page_order;
>> + zero_hugepage_dev_info.batch_size = batch_size;
>> + zero_hugepage_dev_info.delay_jiffies = msecs_to_jiffies(delay_millisecs);
>> +
>> + err |= hugepage_reporting_register(&zero_hugepage_dev_info);
>> pr_info("Zero page enabled\n");
>> } else {
>> page_reporting_unregister(&zero_page_dev_info);
>> + hugepage_reporting_unregister(&zero_hugepage_dev_info);
>> pr_info("Zero page disabled\n");
>> }
>>
>> @@ -90,7 +99,15 @@ static int restart_kzeropaged(void)
>> zero_page_dev_info.batch_size = batch_size;
>> zero_page_dev_info.delay_jiffies = msecs_to_jiffies(delay_millisecs);
>>
>> + hugepage_reporting_unregister(&zero_hugepage_dev_info);
>> +
>> + zero_hugepage_dev_info.report = zero_free_pages;
>> + zero_hugepage_dev_info.mini_order = mini_page_order;
>> + zero_hugepage_dev_info.batch_size = batch_size;
>> + zero_hugepage_dev_info.delay_jiffies = msecs_to_jiffies(delay_millisecs);
>> +
>> err = page_reporting_register(&zero_page_dev_info);
>> + err |= hugepage_reporting_register(&zero_hugepage_dev_info);
>> pr_info("Zero page enabled\n");
>> }
>>
>>
>
> Free page reporting in virtio-balloon doesn't give you any guarantees
> regarding zeroing of pages. Take a look at the QEMU implementation -
> e.g., with vfio all reports are simply ignored.
>
> Also, I am not sure if mangling such details ("zeroing of pages") into
> the page reporting infrastructure is a good idea.
>
Oh, now I get what you are doing here, you rely on zero_free_pages of
your other patch series and are not relying on virtio-balloon free page
reporting to do the zeroing.
You really should have mentioned that this patch series relies on the
other one and in which way.
--
Thanks,
David / dhildenb
