| Message ID | 1561554600-5274-1-git-send-email-kernelfans@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [PATCHv4] mm/gup: speed up check_and_migrate_cma_pages() on huge page | expand |
On Wed, Jun 26, 2019 at 09:10:00PM +0800, Pingfan Liu wrote: > Both hugetlb and thp locate on the same migration type of pageblock, since > they are allocated from a free_list[]. Based on this fact, it is enough to > check on a single subpage to decide the migration type of the whole huge > page. By this way, it saves (2M/4K - 1) times loop for pmd_huge on x86, > similar on other archs. > > Furthermore, when executing isolate_huge_page(), it avoid taking global > hugetlb_lock many times, and meanless remove/add to the local link list > cma_page_list. > > Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Ira Weiny <ira.weiny@intel.com> > Cc: Mike Rapoport <rppt@linux.ibm.com> > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: John Hubbard <jhubbard@nvidia.com> > Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Keith Busch <keith.busch@intel.com> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > Cc: Linux-kernel@vger.kernel.org > --- > v3 -> v4: fix C language precedence issue > > mm/gup.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index ddde097..ffca55b 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1342,19 +1342,22 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, > LIST_HEAD(cma_page_list); > > check_again: > - for (i = 0; i < nr_pages; i++) { > + for (i = 0; i < nr_pages;) { > + > + struct page *head = compound_head(pages[i]); > + long step = 1; > + > + if (PageCompound(head)) > + step = (1 << compound_order(head)) - (pages[i] - head); > /* > * If we get a page from the CMA zone, since we are going to > * be pinning these entries, we might as well move them out > * of the CMA zone if possible. > */ > - if (is_migrate_cma_page(pages[i])) { > - > - struct page *head = compound_head(pages[i]); > - > - if (PageHuge(head)) { > + if (is_migrate_cma_page(head)) { > + if (PageHuge(head)) > isolate_huge_page(head, &cma_page_list); > - } else { > + else { > if (!PageLRU(head) && drain_allow) { > lru_add_drain_all(); > drain_allow = false; > @@ -1369,6 +1372,8 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, > } > } > } > + > + i += step; > } > > if (!list_empty(&cma_page_list)) { > -- > 2.7.5 >
On Wed, 26 Jun 2019 21:10:00 +0800 Pingfan Liu <kernelfans@gmail.com> wrote: > Both hugetlb and thp locate on the same migration type of pageblock, since > they are allocated from a free_list[]. Based on this fact, it is enough to > check on a single subpage to decide the migration type of the whole huge > page. By this way, it saves (2M/4K - 1) times loop for pmd_huge on x86, > similar on other archs. > > Furthermore, when executing isolate_huge_page(), it avoid taking global > hugetlb_lock many times, and meanless remove/add to the local link list > cma_page_list. > > ... > > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1342,19 +1342,22 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, > LIST_HEAD(cma_page_list); > > check_again: > - for (i = 0; i < nr_pages; i++) { > + for (i = 0; i < nr_pages;) { > + > + struct page *head = compound_head(pages[i]); > + long step = 1; > + > + if (PageCompound(head)) I suspect this would work correctly if the PageCompound test was simply removed. Not that I'm really suggesting that it be removed - dunno. > + step = (1 << compound_order(head)) - (pages[i] - head); I don't understand this statement. Why does the position of this page in the pages[] array affect anything? There's an assumption about the contents of the skipped pages, I assume. Could we please get a comment in here whcih fully explains the logic and any assumptions?
On Thu, Jun 27, 2019 at 7:15 AM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Wed, 26 Jun 2019 21:10:00 +0800 Pingfan Liu <kernelfans@gmail.com> wrote: > > > Both hugetlb and thp locate on the same migration type of pageblock, since > > they are allocated from a free_list[]. Based on this fact, it is enough to > > check on a single subpage to decide the migration type of the whole huge > > page. By this way, it saves (2M/4K - 1) times loop for pmd_huge on x86, > > similar on other archs. > > > > Furthermore, when executing isolate_huge_page(), it avoid taking global > > hugetlb_lock many times, and meanless remove/add to the local link list > > cma_page_list. > > > > ... > > > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -1342,19 +1342,22 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, > > LIST_HEAD(cma_page_list); > > > > check_again: > > - for (i = 0; i < nr_pages; i++) { > > + for (i = 0; i < nr_pages;) { > > + > > + struct page *head = compound_head(pages[i]); > > + long step = 1; > > + > > + if (PageCompound(head)) > > I suspect this would work correctly if the PageCompound test was simply > removed. Not that I'm really suggesting that it be removed - dunno. Yes, you are right. compound_order() can safely run on normal page, which means we can drop the check PageCompound(). > > > + step = (1 << compound_order(head)) - (pages[i] - head); > > I don't understand this statement. Why does the position of this page > in the pages[] array affect anything? There's an assumption about the > contents of the skipped pages, I assume. Because gup may start from a tail page. > > Could we please get a comment in here whcih fully explains the logic > and any assumptions? Sure, I will. Thanks, Pingfan >
diff --git a/mm/gup.c b/mm/gup.c index ddde097..ffca55b 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1342,19 +1342,22 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, LIST_HEAD(cma_page_list); check_again: - for (i = 0; i < nr_pages; i++) { + for (i = 0; i < nr_pages;) { + + struct page *head = compound_head(pages[i]); + long step = 1; + + if (PageCompound(head)) + step = (1 << compound_order(head)) - (pages[i] - head); /* * If we get a page from the CMA zone, since we are going to * be pinning these entries, we might as well move them out * of the CMA zone if possible. */ - if (is_migrate_cma_page(pages[i])) { - - struct page *head = compound_head(pages[i]); - - if (PageHuge(head)) { + if (is_migrate_cma_page(head)) { + if (PageHuge(head)) isolate_huge_page(head, &cma_page_list); - } else { + else { if (!PageLRU(head) && drain_allow) { lru_add_drain_all(); drain_allow = false; @@ -1369,6 +1372,8 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, } } } + + i += step; } if (!list_empty(&cma_page_list)) {
Both hugetlb and thp locate on the same migration type of pageblock, since they are allocated from a free_list[]. Based on this fact, it is enough to check on a single subpage to decide the migration type of the whole huge page. By this way, it saves (2M/4K - 1) times loop for pmd_huge on x86, similar on other archs. Furthermore, when executing isolate_huge_page(), it avoid taking global hugetlb_lock many times, and meanless remove/add to the local link list cma_page_list. Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Mike Rapoport <rppt@linux.ibm.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: John Hubbard <jhubbard@nvidia.com> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Keith Busch <keith.busch@intel.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Linux-kernel@vger.kernel.org --- v3 -> v4: fix C language precedence issue mm/gup.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)