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Shutemov" X-Google-Original-From: "Kirill A. Shutemov" Received: by box.localdomain (Postfix, from userid 1000) id 7673A100D2A; Fri, 27 Mar 2020 20:06:07 +0300 (+03) To: akpm@linux-foundation.org, Andrea Arcangeli Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCH 5/7] khugepaged: Allow to collapse PTE-mapped compound pages Date: Fri, 27 Mar 2020 20:05:59 +0300 Message-Id: <20200327170601.18563-6-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.26.0 In-Reply-To: <20200327170601.18563-1-kirill.shutemov@linux.intel.com> References: <20200327170601.18563-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: We can collapse PTE-mapped compound pages. We only need to avoid handling them more than once: lock/unlock page only once if it's present in the PMD range multiple times as it handled on compound level. The same goes for LRU isolation and putpack. Signed-off-by: Kirill A. Shutemov --- mm/khugepaged.c | 41 +++++++++++++++++++++++++++++++---------- 1 file changed, 31 insertions(+), 10 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index b47edfe57f7b..c8c2c463095c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -515,6 +515,17 @@ void __khugepaged_exit(struct mm_struct *mm) =20 static void release_pte_page(struct page *page) { + /* + * We need to unlock and put compound page on LRU only once. + * The rest of the pages have to be locked and not on LRU here. + */ + VM_BUG_ON_PAGE(!PageCompound(page) && + (!PageLocked(page) && PageLRU(page)), page); + + if (!PageLocked(page)) + return; + + page =3D compound_head(page); dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); unlock_page(page); putback_lru_page(page); @@ -537,6 +548,7 @@ static int __collapse_huge_page_isolate(struct vm_are= a_struct *vma, pte_t *_pte; int none_or_zero =3D 0, result =3D 0, referenced =3D 0; bool writable =3D false; + LIST_HEAD(compound_pagelist); =20 for (_pte =3D pte; _pte < pte+HPAGE_PMD_NR; _pte++, address +=3D PAGE_SIZE) { @@ -561,13 +573,23 @@ static int __collapse_huge_page_isolate(struct vm_a= rea_struct *vma, goto out; } =20 - /* TODO: teach khugepaged to collapse THP mapped with pte */ + VM_BUG_ON_PAGE(!PageAnon(page), page); + if (PageCompound(page)) { - result =3D SCAN_PAGE_COMPOUND; - goto out; - } + struct page *p; + page =3D compound_head(page); =20 - VM_BUG_ON_PAGE(!PageAnon(page), page); + /* + * Check if we have dealt with the compount page + * already + */ + list_for_each_entry(p, &compound_pagelist, lru) { + if (page =3D=3D p) + break; + } + if (page =3D=3D p) + continue; + } =20 /* * We can do it before isolate_lru_page because the @@ -640,6 +662,9 @@ static int __collapse_huge_page_isolate(struct vm_are= a_struct *vma, page_is_young(page) || PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm, address)) referenced++; + + if (PageCompound(page)) + list_add_tail(&page->lru, &compound_pagelist); } if (likely(writable)) { if (likely(referenced)) { @@ -1185,11 +1210,7 @@ static int khugepaged_scan_pmd(struct mm_struct *m= m, goto out_unmap; } =20 - /* TODO: teach khugepaged to collapse THP mapped with pte */ - if (PageCompound(page)) { - result =3D SCAN_PAGE_COMPOUND; - goto out_unmap; - } + page =3D compound_head(page); =20 /* * Record which node the original page is from and save this --=20 2.26.0