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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773154499; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4Koap7c4nmBUn1jQcRs2TKnT3RilQxG9yZc8gbf4yHA=; b=Q7J9Xayb3tuq1RwczoR+kkYcwmbHr2IBdva+1kWyUfpOmeUqFxY8p3HhUG0VvkvFVRO7cq rcbAym+WsHWFr//SsTKMXbfjnthBN1AVMJKC4S1BQIu+Y4f+asu6YqEK9FjMKM6HNAuqFg o+kIhQjL1lj8wyLdBd5OI3jV01FKMB4= From: Usama Arif To: Andrew Morton , ryan.roberts@arm.com, david@kernel.org Cc: ajd@linux.ibm.com, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, brauner@kernel.org, catalin.marinas@arm.com, dev.jain@arm.com, jack@suse.cz, kees@kernel.org, kevin.brodsky@arm.com, lance.yang@linux.dev, Liam.Howlett@oracle.com, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, npache@redhat.com, rmclure@linux.ibm.com, Al Viro , will@kernel.org, willy@infradead.org, ziy@nvidia.com, hannes@cmpxchg.org, kas@kernel.org, shakeel.butt@linux.dev, kernel-team@meta.com, Usama Arif Subject: [PATCH 4/4] mm: align file-backed mmap to exec folio order in thp_get_unmapped_area Date: Tue, 10 Mar 2026 07:51:17 -0700 Message-ID: <20260310145406.3073394-5-usama.arif@linux.dev> In-Reply-To: <20260310145406.3073394-1-usama.arif@linux.dev> References: <20260310145406.3073394-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: u48wfk8ghkboh1ew4yod7odg4tcjf9j9 X-Rspam-User: X-Rspamd-Queue-Id: 600AB180008 X-Rspamd-Server: rspam12 X-HE-Tag: 1773154501-16187 X-HE-Meta: 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 UNy3USg6 455o/to5TFWHrFiCgPMFVoBtLRTh/QPvB1bHtV1LZStz+UjXkx8ToZsG7kMbTFLitrPfMZ/bsTDX1SDGf7MbonZkUfgbFvVn5hnIWi/V/XwIi3bogvpm9mNpeIOAuAFpnRe3fuDis/wObr8ARdZcr1ZAxXabhxe4DehNrgNALXjtjmvw1JsffABqPYu2DS+GahXhX6/53RwRFGzJJfUQzNA7Ixtb0zyu7f2bNk7ASXi3aJsFnQhYXP7x+IQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: thp_get_unmapped_area() is the get_unmapped_area callback for filesystems like ext4, xfs, and btrfs. It attempts to align the virtual address for PMD_SIZE THP mappings, but on arm64 with 64K base pages PMD_SIZE is 512M, which is too large for typical shared library mappings, so the alignment always fails and falls back to PAGE_SIZE. This means shared libraries loaded by ld.so via mmap() get 64K-aligned virtual addresses, preventing contpte mapping even when 2M folios are allocated with properly aligned file offsets and physical addresses. Add a fallback in thp_get_unmapped_area_vmflags() that tries PAGE_SIZE << exec_folio_order() alignment (2M on arm64 64K pages) when PMD_SIZE alignment fails. This is small enough that shared libraries could qualify, enabling contpte mapping for their executable segments. This applies to all file-backed mappings (not just exec). Non-exec file-backed mappings also benefit from contpte mapping when large folios are used. Aligning all file-backed mappings ensures that any large folio in the page cache can be contpte-mapped regardless of the mapping's protection flags, reducing dTLB misses for read-heavy workloads. The fallback is gated by exec_folio_order() which returns 0 by default, making this a no-op on architectures that don't define it. Signed-off-by: Usama Arif --- mm/huge_memory.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 8e2746ea74adf..1c9476a5ed51c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1242,6 +1242,23 @@ unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long add if (ret) return ret; + /* + * If the arch requested large folios for exec memory, try to align + * to the folio size as a fallback. This is much smaller than PMD_SIZE + * (e.g. 2M vs 512M on arm64 64K pages), so it succeeds for mappings + * that are too small for PMD alignment. Proper alignment ensures that + * the hardware can coalesce PTEs (e.g. arm64 contpte) when large + * folios are mapped. + */ + if (exec_folio_order()) { + unsigned long folio_size = PAGE_SIZE << exec_folio_order(); + + ret = __thp_get_unmapped_area(filp, addr, len, off, flags, + folio_size, vm_flags); + if (ret) + return ret; + } + return mm_get_unmapped_area_vmflags(filp, addr, len, pgoff, flags, vm_flags); } -- 2.47.3