On 4/7/24 12:19 PM, Baolin Wang wrote:
> On 2024/3/21 02:02, Johannes Weiner wrote:
>>
>> + account_freepages(page, zone, 1 << order, migratetype);
>> +
>> while (order < MAX_PAGE_ORDER) {
>> - if (compaction_capture(capc, page, order, migratetype)) {
>> - __mod_zone_freepage_state(zone, -(1 << order),
>> - migratetype);
>> + int buddy_mt = migratetype;
>> +
>> + if (compaction_capture(capc, page, order, migratetype))
>> return;
>> - }
>
> IIUC, if the released page is captured by compaction, then the
> statistics for free pages should be correspondingly decreased,
> otherwise, there will be a slight regression for my thpcompact benchmark.
>
> thpcompact Percentage Faults Huge
> k6.9-rc2-base base + patch10 + 2 fixes
> Percentage huge-1 78.18 ( 0.00%) 71.92 ( -8.01%)
> Percentage huge-3 86.70 ( 0.00%) 86.07 ( -0.73%)
> Percentage huge-5 90.26 ( 0.00%) 78.02 ( -13.57%)
> Percentage huge-7 92.34 ( 0.00%) 78.67 ( -14.81%)
> Percentage huge-12 91.18 ( 0.00%) 81.04 ( -11.12%)
> Percentage huge-18 89.00 ( 0.00%) 79.57 ( -10.60%)
> Percentage huge-24 90.52 ( 0.00%) 80.07 ( -11.54%)
> Percentage huge-30 94.44 ( 0.00%) 96.28 ( 1.95%)
> Percentage huge-32 93.09 ( 0.00%) 99.39 ( 6.77%)
>
> I add below fix based on your fix 2, then the thpcompact Percentage
> looks good. How do you think for the fix?
Yeah another well spotted, thanks. "slight regression" is an understatement,
this affects not just a "statistics" but very important counter
NR_FREE_PAGES which IIUC would eventually become larger than reality, make
the watermark checks false positive and result in depleted reserves etc etc.
Actually wondering why we're not seeing -next failures already (or maybe I
just haven't noticed).
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 8330c5c2de6b..2facf844ef84 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -805,8 +805,10 @@ static inline void __free_one_page(struct page *page,
> while (order < MAX_PAGE_ORDER) {
> int buddy_mt = migratetype;
>
> - if (compaction_capture(capc, page, order, migratetype))
> + if (compaction_capture(capc, page, order, migratetype)) {
> + account_freepages(zone, -(1 << order), migratetype);
> return;
> + }
>
> buddy = find_buddy_page_pfn(page, pfn, order, &buddy_pfn);
> if (!buddy)
>
> With my fix, the THP percentage looks better:
> k6.9-rc2-base base + patch10 + 2 fixes +
> my fix
> Percentage huge-1 78.18 ( 0.00%) 82.83 ( 5.94%)
> Percentage huge-3 86.70 ( 0.00%) 93.47 ( 7.81%)
> Percentage huge-5 90.26 ( 0.00%) 94.73 ( 4.95%)
> Percentage huge-7 92.34 ( 0.00%) 95.22 ( 3.12%)
> Percentage huge-12 91.18 ( 0.00%) 92.40 ( 1.34%)
> Percentage huge-18 89.00 ( 0.00%) 85.39 ( -4.06%)
> Percentage huge-24 90.52 ( 0.00%) 94.70 ( 4.61%)
> Percentage huge-30 94.44 ( 0.00%) 97.00 ( 2.71%)
> Percentage huge-32 93.09 ( 0.00%) 92.87 ( -0.24%)
