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Mon, 14 Apr 2025 23:18:54 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.91]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 09A731808867; Mon, 14 Apr 2025 23:18:43 +0000 (UTC) From: Nico Pache To: npache@redhat.com Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@redhat.com, dev.jain@arm.com, hannes@cmpxchg.org, jack@suse.cz, jglisse@google.com, kirill.shutemov@linux.intel.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, raquini@redhat.com, rientjes@google.com, rostedt@goodmis.org, ryan.roberts@arm.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ziy@nvidia.com, zokeefe@google.com Subject: [PATCH v4 06/12] khugepaged: introduce khugepaged_scan_bitmap for mTHP support Date: Mon, 14 Apr 2025 17:18:28 -0600 Message-ID: <20250414231828.59151-1-npache@redhat.com> In-Reply-To: <20250414220557.35388-7-npache@redhat.com> References: <20250414220557.35388-7-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: E74884000E X-Stat-Signature: 8q8ecmjbkgx8383q9zaqao9cmi6rzy63 X-Rspam-User: X-HE-Tag: 1744672743-683931 X-HE-Meta: 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 arhmvVmf UucKdeyCfbDzPJ+gQKr0PXwfDDlqUKr26vEgIL65uxOkYGeIU96E+aMPGim6Or/oaz+6Cen42SINgK4Ru9nSxMX0iXc57UutJ52TPSV1aJ+lNqhPb4XG+6KX2PKiXwuJ0HjmqMMx6dMVw2nhR1xWU1C51sfqo0n5+8yIuoG+CIG2hftgZx3F/rWGy5SH72pLoWe9Cq+LQN6jFkHDVNsAkRbG3mOi3/lgOETdW1PcS1dl5C/zinldnxI2Gb7oQiUJvWKPOaxEwT9FnhNpTKuV+g53PdhKnibn10dd+JjlmC1Pe7ShgueFbL3YmCbAcoNqgAmmfw/Tv5cKZVzwpYGn/s+h5ELyNmm3cQOeV5SpW2z4AGGd16Y/vUInAKAa9T3NpUtF9i7ti77ns0RDHGFk17CB2wh2d1QZD5xa8U/H/zw3NfttuqUYohVIRwPdNrNcts1wXedjFvchruVo= 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: List-Subscribe: List-Unsubscribe: khugepaged scans PMD ranges for potential collapse to a hugepage. To add mTHP support we use this scan to instead record chunks of utilized sections of the PMD. khugepaged_scan_bitmap uses a stack struct to recursively scan a bitmap that represents chunks of utilized regions. We can then determine what mTHP size fits best and in the following patch, we set this bitmap while scanning the PMD. max_ptes_none is used as a scale to determine how "full" an order must be before being considered for collapse. When attempting to collapse an order that has its order set to "always" lets always collapse to that order in a greedy manner without considering the number of bits set. Signed-off-by: Nico Pache --- include/linux/khugepaged.h | 4 ++ mm/khugepaged.c | 94 ++++++++++++++++++++++++++++++++++---- 2 files changed, 89 insertions(+), 9 deletions(-) diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h index 1f46046080f5..18fe6eb5051d 100644 --- a/include/linux/khugepaged.h +++ b/include/linux/khugepaged.h @@ -1,6 +1,10 @@ /* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_KHUGEPAGED_H #define _LINUX_KHUGEPAGED_H +#define KHUGEPAGED_MIN_MTHP_ORDER 2 +#define KHUGEPAGED_MIN_MTHP_NR (1<mthp_bitmap_stack[++top] = (struct scan_bit_state) + { HPAGE_PMD_ORDER - KHUGEPAGED_MIN_MTHP_ORDER, 0 }; + + while (top >= 0) { + state = cc->mthp_bitmap_stack[top--]; + order = state.order + KHUGEPAGED_MIN_MTHP_ORDER; + offset = state.offset; + num_chunks = 1 << (state.order); + // Skip mTHP orders that are not enabled + if (!test_bit(order, &enabled_orders)) + goto next; + + // copy the relavant section to a new bitmap + bitmap_shift_right(cc->mthp_bitmap_temp, cc->mthp_bitmap, offset, + MTHP_BITMAP_SIZE); + + bits_set = bitmap_weight(cc->mthp_bitmap_temp, num_chunks); + threshold_bits = (HPAGE_PMD_NR - khugepaged_max_ptes_none - 1) + >> (HPAGE_PMD_ORDER - state.order); + + //Check if the region is "almost full" based on the threshold + if (bits_set > threshold_bits || is_pmd_only + || test_bit(order, &huge_anon_orders_always)) { + ret = collapse_huge_page(mm, address, referenced, unmapped, cc, + mmap_locked, order, offset * KHUGEPAGED_MIN_MTHP_NR); + if (ret == SCAN_SUCCEED) { + collapsed += (1 << order); + continue; + } + } + +next: + if (state.order > 0) { + next_order = state.order - 1; + mid_offset = offset + (num_chunks / 2); + cc->mthp_bitmap_stack[++top] = (struct scan_bit_state) + { next_order, mid_offset }; + cc->mthp_bitmap_stack[++top] = (struct scan_bit_state) + { next_order, offset }; + } + } + return collapsed; +} + static int khugepaged_scan_pmd(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, bool *mmap_locked, @@ -1445,9 +1523,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, pte_unmap_unlock(pte, ptl); if (result == SCAN_SUCCEED) { result = collapse_huge_page(mm, address, referenced, - unmapped, cc); - /* collapse_huge_page will return with the mmap_lock released */ - *mmap_locked = false; + unmapped, cc, mmap_locked, HPAGE_PMD_ORDER, 0); } out: trace_mm_khugepaged_scan_pmd(mm, &folio->page, writable, referenced,