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Sun, 13 Jul 2025 20:34:11 -0400 X-MC-Unique: QH7DM3DINQScaWt3TqbM6g-1 X-Mimecast-MFC-AGG-ID: QH7DM3DINQScaWt3TqbM6g_1752453247 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B273E18011EF; Mon, 14 Jul 2025 00:34:06 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.9]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E14CA30001A1; Mon, 14 Jul 2025 00:33:53 +0000 (UTC) From: Nico Pache To: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org, hughd@google.com Subject: [PATCH v9 06/14] khugepaged: introduce collapse_scan_bitmap for mTHP support Date: Sun, 13 Jul 2025 18:31:59 -0600 Message-ID: <20250714003207.113275-7-npache@redhat.com> In-Reply-To: <20250714003207.113275-1-npache@redhat.com> References: <20250714003207.113275-1-npache@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 50AB64000D X-Stat-Signature: zi9u9yek36asp16rk3aquyc6tpbpj4q9 X-Rspam-User: X-HE-Tag: 1752453255-748467 X-HE-Meta: U2FsdGVkX18qaFX5SJ6N1f70aE5MZZeiSv2Hb05+dAggByRx92aSckmJOuQ7zVsILHsypWa+uksVhpdL8oLtSkA5GWI/rGSm9V5SP4eN60vcBjkJEjG0ooHIFaC1WmD/WXoIXzNiGq3f7XMdCOycdl9h6cEAPgZ633kcMX33Fgbhz7AceeHwfz7LtBQMYGMuzM/kdCbRnwALSeP/ycuC1/fV2XSc8I4u/9j5/5ZxRMzPbf/x+UxGUtuDOnTnszF/x/jFXTBU/dJNRNl6lsARjZaKPaOLwGThT9IUXhySMHZQIeU10NzJxL2G+Ec78uC4l4sCb5yxv0+H2y5RTjg+wtvbv0/mAxd9Zo1RmdD1laisasZhq8u+b43AGOiK82+bfYQQOTPUwwjRjEh54A9JXsBW1r9SGllgeJZsLEBGfNZE6g3CwpsNGFCm8cy6sC5WcJqvVmeUoPoWZNRm4wPoA0FqodjZS2hAe0E+gy11vtN4qe5Hn8ydets/otU4rwzwkDB+Qpady/oOeKuwWZ9k27nnwQEQxjqiCjexxhtX9gKpfyQrwfdF5pkjISwUh5N4ImRrxMWb8Z47T7721h4Da+IW9UoKVOGcHN9W106iZ9i2xxLNscmvCkqD9Xp4aTADZKgKIBVykcy7GB9DBt1UUJj3f13IdDx4kRI0Yl5MOFwO0CXZHvoiZUjy1fQ74+cBvtfHaIvGBtahuf85vGkSIs7Ptrk7Fma0aqK/agUQO8ROUMJGlgwrKB0rVahUch0ybTQDORWHiCuJOoGAsxtftqUJMduqfIqPu191rgMORzWklJgcfpmWQ3cmfKTkzjhrD2x34aQrlNXW0mz+D79wdGyrLvaB+ddrrP4e/FpBvTkSnWrWoWRknZjLBfnuK3w89ATT0DGCfvbko7iXLDOOY6b1jr5an4x+2no+uDmuwdzTcegvk9Hw1WhaSBzRFK6vueSlVLncv9ewy46gvhn rfwQewZ6 U7psrmu77CtAlthN0G2/L0YYXovD+b7EqAqCUMmAFloBisctPAaROYrdVR6l35T9x6OPqO428oT9T2yBZgvQASu+wpGfPIfmIG9fs1hxXyvYYNwnlw3xzK3Cm2263+XsD10UySY5lc1o8UXHIfUzP1lsAZ28GW8q2TvT/92WMwnA2qKmrGO1WxPxTgOiapHyvc7KgUYeNQuy1mTGfabh8IhklJj8xsypWMCZiIX573ci5Bm9F027cA1OIhw8Fg49ZEl1iW7Bv2RTSdeDiA4mlVdSIilyF3Mz9SWynIedFGspieNJLIVYNzjRgPLKEm/xYjhz/meSZ/vadxzwIVh8gLjx1ma1Zz/6exi9gVhFY1CaTWAaATY5JJ0gGlvOtWlbos77mFsAXWMfWKFp0Fiquc8ljUXSvZJrLhgloi3mbpzeu4BuCOvAfulxtJ/HAcuN5iRqshJHwODdcWsA= 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 anons 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. collapse_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 anon PMD. A minimum collapse order of 2 is used as this is the lowest order supported by anon memory. 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 ff6120463745..0f957711a117 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 collapse_scan_pmd(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, bool *mmap_locked, @@ -1444,9 +1522,7 @@ static int collapse_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, writable, referenced, -- 2.50.0