Re: [PATCH v4 2/4] mm/page_reporting: Export reporting order as module parameter

[Gavin Shan <gshan@redhat.com>]

On 6/25/21 11:14 AM, Alexander Duyck wrote:
> On Thu, Jun 24, 2021 at 4:46 PM Gavin Shan <gshan@redhat.com> wrote:
>>
>> The macro PAGE_REPORTING_MIN_ORDER is defined as the page reporting
>> threshold. It can't be adjusted at runtime.
>>
>> This introduces a variable (@page_reporting_order) to replace the
>> marcro (PAGE_REPORTING_MIN_ORDER). MAX_ORDER is assigned to it initially,
>> meaning the page reporting is disabled. It will be specified by driver
>> if valid one is provided. Otherwise, it will fall back to @pageblock_order.
>> It's also exported so that the page reporting order can be adjusted at
>> runtime.
>>
>> Suggested-by: David Hildenbrand <david@redhat.com>
>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>> Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
> 
> So this patch looks like it is technically broken. We need a line in
> page_reporting_register that will overwrite the value with
> pageblock_order if it is less than page_reporting_order.
> 

Yes, but it's not broken after next (PATCH[3/4]) is applied.
However, It's still worthy to be fixed, to be "git bisect"
friendly. I'll update in v5.

Thanks,
Gavin

>> ---
>>   Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
>>   mm/page_reporting.c                             | 9 +++++++--
>>   mm/page_reporting.h                             | 5 ++---
>>   3 files changed, 15 insertions(+), 5 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index cb89dbdedc46..566c4b9af3cd 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -3566,6 +3566,12 @@
>>                          off: turn off poisoning (default)
>>                          on: turn on poisoning
>>
>> +       page_reporting.page_reporting_order=
>> +                       [KNL] Minimal page reporting order
>> +                       Format: <integer>
>> +                       Adjust the minimal page reporting order. The page
>> +                       reporting is disabled when it exceeds (MAX_ORDER-1).
>> +
>>          panic=          [KNL] Kernel behaviour on panic: delay <timeout>
>>                          timeout > 0: seconds before rebooting
>>                          timeout = 0: wait forever
>> diff --git a/mm/page_reporting.c b/mm/page_reporting.c
>> index df9c5054e1b4..34bf4d26c2c4 100644
>> --- a/mm/page_reporting.c
>> +++ b/mm/page_reporting.c
>> @@ -4,12 +4,17 @@
>>   #include <linux/page_reporting.h>
>>   #include <linux/gfp.h>
>>   #include <linux/export.h>
>> +#include <linux/module.h>
>>   #include <linux/delay.h>
>>   #include <linux/scatterlist.h>
>>
>>   #include "page_reporting.h"
>>   #include "internal.h"
>>
>> +unsigned int page_reporting_order = MAX_ORDER;
>> +module_param(page_reporting_order, uint, 0644);
>> +MODULE_PARM_DESC(page_reporting_order, "Set page reporting order");
>> +
>>   #define PAGE_REPORTING_DELAY   (2 * HZ)
>>   static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly;
>>
>> @@ -229,7 +234,7 @@ page_reporting_process_zone(struct page_reporting_dev_info *prdev,
>>
>>          /* Generate minimum watermark to be able to guarantee progress */
>>          watermark = low_wmark_pages(zone) +
>> -                   (PAGE_REPORTING_CAPACITY << PAGE_REPORTING_MIN_ORDER);
>> +                   (PAGE_REPORTING_CAPACITY << page_reporting_order);
>>
>>          /*
>>           * Cancel request if insufficient free memory or if we failed
>> @@ -239,7 +244,7 @@ page_reporting_process_zone(struct page_reporting_dev_info *prdev,
>>                  return err;
>>
>>          /* Process each free list starting from lowest order/mt */
>> -       for (order = PAGE_REPORTING_MIN_ORDER; order < MAX_ORDER; order++) {
>> +       for (order = page_reporting_order; order < MAX_ORDER; order++) {
>>                  for (mt = 0; mt < MIGRATE_TYPES; mt++) {
>>                          /* We do not pull pages from the isolate free list */
>>                          if (is_migrate_isolate(mt))
>> diff --git a/mm/page_reporting.h b/mm/page_reporting.h
>> index 2c385dd4ddbd..c51dbc228b94 100644
>> --- a/mm/page_reporting.h
>> +++ b/mm/page_reporting.h
>> @@ -10,10 +10,9 @@
>>   #include <linux/pgtable.h>
>>   #include <linux/scatterlist.h>
>>
>> -#define PAGE_REPORTING_MIN_ORDER       pageblock_order
>> -
>>   #ifdef CONFIG_PAGE_REPORTING
>>   DECLARE_STATIC_KEY_FALSE(page_reporting_enabled);
>> +extern unsigned int page_reporting_order;
>>   void __page_reporting_notify(void);
>>
>>   static inline bool page_reported(struct page *page)
>> @@ -38,7 +37,7 @@ static inline void page_reporting_notify_free(unsigned int order)
>>                  return;
>>
>>          /* Determine if we have crossed reporting threshold */
>> -       if (order < PAGE_REPORTING_MIN_ORDER)
>> +       if (order < page_reporting_order)
>>                  return;
>>
>>          /* This will add a few cycles, but should be called infrequently */
>> --
>> 2.23.0
>>
>