| Message ID | 20221230093020.9664-1-wangkefeng.wang@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] mm: huge_memory: convert split_huge_pages_all() to use a folio | expand |
On Fri, 30 Dec 2022 17:30:20 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote: > Straightforwardly convert split_huge_pages_all() to use a folio. > > ... > > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2932,6 +2932,7 @@ static void split_huge_pages_all(void) > { > struct zone *zone; > struct page *page; > + struct folio *folio; > unsigned long pfn, max_zone_pfn; > unsigned long total = 0, split = 0; > > @@ -2944,24 +2945,32 @@ static void split_huge_pages_all(void) > int nr_pages; > > page = pfn_to_online_page(pfn); > - if (!page || !get_page_unless_zero(page)) > + if (!page || PageTail(page)) > + continue; > + folio = page_folio(page); > + if (!folio_try_get(folio)) > continue; > > - if (zone != page_zone(page)) > + if (unlikely(page_folio(page) != folio)) > + goto next; > + > + if (zone != folio_zone(folio)) > goto next; I'm still not understanding the above hunk. Why is the "page_folio(page) != folio" check added? Should it be commented? > - if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) > + if (!folio_test_large(folio) || > + folio_test_hugetlb(folio) || > + !folio_test_lru(folio)) > goto next; > > total++; > - lock_page(page); > - nr_pages = thp_nr_pages(page); > - if (!split_huge_page(page)) > + folio_lock(folio); > + nr_pages = folio_nr_pages(folio); > + if (!split_folio(folio)) > split++; > pfn += nr_pages - 1; > - unlock_page(page); > + folio_unlock(folio); > next: > - put_page(page); > + folio_put(folio); > cond_resched(); > } > } > -- > 2.35.3
On 2022/12/31 5:45, Andrew Morton wrote: > On Fri, 30 Dec 2022 17:30:20 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote: > >> Straightforwardly convert split_huge_pages_all() to use a folio. >> >> ... >> >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -2932,6 +2932,7 @@ static void split_huge_pages_all(void) >> { >> struct zone *zone; >> struct page *page; >> + struct folio *folio; >> unsigned long pfn, max_zone_pfn; >> unsigned long total = 0, split = 0; >> >> @@ -2944,24 +2945,32 @@ static void split_huge_pages_all(void) >> int nr_pages; >> >> page = pfn_to_online_page(pfn); >> - if (!page || !get_page_unless_zero(page)) >> + if (!page || PageTail(page)) >> + continue; >> + folio = page_folio(page); >> + if (!folio_try_get(folio)) >> continue; >> >> - if (zone != page_zone(page)) >> + if (unlikely(page_folio(page) != folio)) >> + goto next; >> + >> + if (zone != folio_zone(folio)) >> goto next; > > I'm still not understanding the above hunk. Why is the > "page_folio(page) != folio" check added? Should it be commented? There is a comment in try_get_folio(), is it enough?
On Tue, 3 Jan 2023 09:58:36 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote: > > > On 2022/12/31 5:45, Andrew Morton wrote: > > On Fri, 30 Dec 2022 17:30:20 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote: > > > >> Straightforwardly convert split_huge_pages_all() to use a folio. > >> > >> ... > >> > >> --- a/mm/huge_memory.c > >> +++ b/mm/huge_memory.c > >> @@ -2932,6 +2932,7 @@ static void split_huge_pages_all(void) > >> { > >> struct zone *zone; > >> struct page *page; > >> + struct folio *folio; > >> unsigned long pfn, max_zone_pfn; > >> unsigned long total = 0, split = 0; > >> > >> @@ -2944,24 +2945,32 @@ static void split_huge_pages_all(void) > >> int nr_pages; > >> > >> page = pfn_to_online_page(pfn); > >> - if (!page || !get_page_unless_zero(page)) > >> + if (!page || PageTail(page)) > >> + continue; > >> + folio = page_folio(page); > >> + if (!folio_try_get(folio)) > >> continue; > >> > >> - if (zone != page_zone(page)) > >> + if (unlikely(page_folio(page) != folio)) > >> + goto next; > >> + > >> + if (zone != folio_zone(folio)) > >> goto next; > > > > I'm still not understanding the above hunk. Why is the > > "page_folio(page) != folio" check added? Should it be commented? > > There is a comment in try_get_folio(), is it enough? Nobody would think to look at a private function in gup.c. I suggest this folio_try_get() rule be documented at the folio_try_get() implementation site. Most callers do perform this check, but not the ones in vmscan.c?
On 2023/1/6 11:06, Andrew Morton wrote: > On Tue, 3 Jan 2023 09:58:36 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote: > >> >> >> On 2022/12/31 5:45, Andrew Morton wrote: >>> On Fri, 30 Dec 2022 17:30:20 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote: >>> >>>> Straightforwardly convert split_huge_pages_all() to use a folio. >>>> >>>> ... >>>> >>>> --- a/mm/huge_memory.c >>>> +++ b/mm/huge_memory.c >>>> @@ -2932,6 +2932,7 @@ static void split_huge_pages_all(void) >>>> { >>>> struct zone *zone; >>>> struct page *page; >>>> + struct folio *folio; >>>> unsigned long pfn, max_zone_pfn; >>>> unsigned long total = 0, split = 0; >>>> >>>> @@ -2944,24 +2945,32 @@ static void split_huge_pages_all(void) >>>> int nr_pages; >>>> >>>> page = pfn_to_online_page(pfn); >>>> - if (!page || !get_page_unless_zero(page)) >>>> + if (!page || PageTail(page)) >>>> + continue; >>>> + folio = page_folio(page); >>>> + if (!folio_try_get(folio)) >>>> continue; >>>> >>>> - if (zone != page_zone(page)) >>>> + if (unlikely(page_folio(page) != folio)) >>>> + goto next; >>>> + >>>> + if (zone != folio_zone(folio)) >>>> goto next; >>> >>> I'm still not understanding the above hunk. Why is the >>> "page_folio(page) != folio" check added? Should it be commented? >> >> There is a comment in try_get_folio(), is it enough? > > Nobody would think to look at a private function in gup.c. Sorry，I mean that comment is to explain why adding a new recheck. > > I suggest this folio_try_get() rule be documented at the > folio_try_get() implementation site. > > Most callers do perform this check, but not the ones in vmscan.c ? Hope Matthew could give some advise, thanks
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 266c4b557946..46e86293935b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2932,6 +2932,7 @@ static void split_huge_pages_all(void) { struct zone *zone; struct page *page; + struct folio *folio; unsigned long pfn, max_zone_pfn; unsigned long total = 0, split = 0; @@ -2944,24 +2945,32 @@ static void split_huge_pages_all(void) int nr_pages; page = pfn_to_online_page(pfn); - if (!page || !get_page_unless_zero(page)) + if (!page || PageTail(page)) + continue; + folio = page_folio(page); + if (!folio_try_get(folio)) continue; - if (zone != page_zone(page)) + if (unlikely(page_folio(page) != folio)) + goto next; + + if (zone != folio_zone(folio)) goto next; - if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) + if (!folio_test_large(folio) || + folio_test_hugetlb(folio) || + !folio_test_lru(folio)) goto next; total++; - lock_page(page); - nr_pages = thp_nr_pages(page); - if (!split_huge_page(page)) + folio_lock(folio); + nr_pages = folio_nr_pages(folio); + if (!split_folio(folio)) split++; pfn += nr_pages - 1; - unlock_page(page); + folio_unlock(folio); next: - put_page(page); + folio_put(folio); cond_resched(); } }
Straightforwardly convert split_huge_pages_all() to use a folio. Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> --- - adjust indenting of code pointed by Matthew mm/huge_memory.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-)