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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779467085; 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=PicG0VGaxNfqAf+Vsr+MRf2Lg77IxoCYcktKo6m1Qck=; b=ibg5Vx7A+wVts3v0jvELrcgu35RAsfd9NMBDgdHVI2I4/3psC/DFKMs3uVXAeo8KquzM+C nx5ARqZbgApa9UptBR7iV3upH3Z43LfvtMI68/Pdozxl84IsBvqwCoQSWYDOgg+Xccwa0C 8LNgGzd8ZjTQt+8DYDpl683S3yYyUwg= From: Usama Arif To: Andrew Morton , david@kernel.org, willy@infradead.org, ryan.roberts@arm.com, linux-mm@kvack.org Cc: r@hev.cc, jack@suse.cz, Andrew Donnellan , apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, brauner@kernel.org, catalin.marinas@arm.com, dev.jain@arm.com, kees@kernel.org, kevin.brodsky@arm.com, lance.yang@linux.dev, Liam R.Howlett , linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ljs@kernel.org, mhocko@suse.com, npache@redhat.com, pasha.tatashin@soleen.com, rmclure@linux.ibm.com, rppt@kernel.org, surenb@google.com, vbabka@kernel.org, Al Viro , wilts.infradead.org@kvack.org, "linux-fsdevel@vger.kernel.l"@kernel.org, ziy@nvidia.com, hannes@cmpxchg.org, kas@kernel.org, shakeel.butt@linux.dev, kernel-team@meta.com, Usama Arif Subject: [PATCH v5 2/2] mm: use mapping_max_folio_order() for force_thp_readahead order Date: Fri, 22 May 2026 09:23:48 -0700 Message-ID: <20260522162422.3856502-3-usama.arif@linux.dev> In-Reply-To: <20260522162422.3856502-1-usama.arif@linux.dev> References: <20260522162422.3856502-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Stat-Signature: draisbyiur7hfc81c4a5paufi8qmrwen X-Rspamd-Queue-Id: BC54C2000B X-Rspam-User: X-HE-Tag: 1779467086-642270 X-HE-Meta: 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 N8wu2Ngt KkfFb/M1lyAwcgNJLpKfAzwCXZR70477910W02PmJJzvR+qH0vHH3OP/JdvFEDqdh0kE1A29hOlsyU5Nx72UOOfzgeiSxpAyUdnR+gVkTL6o4JXfU8Tk0YDkqEIxOSmfcY4bfIXVp1IgRAPpDbE9uki4MP5tNgaqD4afcfYJ9b1UT9uWnc+KB3O/NVJkmAOLCfqUiFuayExr1Nyme888IC68XEgVIAw83HlLA6txl/S6EPCL+FOb2XtlOf8J4/io90YsFrpW670WbsajSRSqKWR1etA1GI+h/2DyA+iWl9Ie1gN6DKATmYxmLMGaMjLtAFeB5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The force_thp_readahead path in do_sync_mmap_readahead() was gated on the compile-time check HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER and always drove the readahead at HPAGE_PMD_ORDER / HPAGE_PMD_NR. On configurations where HPAGE_PMD_ORDER exceeds MAX_PAGECACHE_ORDER -- notably arm64 with a 64K base page size, where HPAGE_PMD_ORDER is 13 (512MB) -- VM_HUGEPAGE mappings could never reach this path and fell back to base-page readahead, even when the mapping itself could serve usefully large folios well below the cap. Widen the gate to min(HPAGE_PMD_ORDER, mapping_max_folio_order(mapping)) <= MAX_PAGECACHE_ORDER so force_thp_readahead engages whenever either order fits, and pick ra->order accordingly: - HPAGE_PMD_ORDER when it fits (existing behaviour); - otherwise min(mapping_max_folio_order(mapping), get_order(SZ_2M)), capping the readahead folio at 2MB regardless of what the mapping advertises. Size and align the readahead window from (1UL << ra->order) instead of the hardcoded HPAGE_PMD_NR / HPAGE_PMD_ORDER so the chosen order is honoured end-to-end. On arm64 with a 64K base page size this lets VM_HUGEPAGE mappings get large-folio readahead at the mapping's supported order (capped at 2MB) rather than dropping back to base pages. 2MB is also the size of an arm64 contiguous-PTE (contpte) block on a 64K base, so the resulting folios coalesce into a single TLB entry and reduce TLB pressure on the readahead path. Signed-off-by: Usama Arif --- mm/filemap.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index f45a1b74870d..56fa715d66cd 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3317,9 +3317,16 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) ractl._max_index = vmf->vma->vm_pgoff + vma_pages(vmf->vma) - 1; /* Use the readahead code, even if readahead is disabled */ - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && - (vm_flags & VM_HUGEPAGE) && HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER) + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && (vm_flags & VM_HUGEPAGE) && + min(HPAGE_PMD_ORDER, mapping_max_folio_order(mapping)) <= MAX_PAGECACHE_ORDER) { force_thp_readahead = true; + if (HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER) + ra->order = HPAGE_PMD_ORDER; + else + ra->order = min_t(unsigned int, + mapping_max_folio_order(mapping), + get_order(SZ_2M)); + } if (!force_thp_readahead) { /* @@ -3354,17 +3361,18 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) } if (force_thp_readahead) { + unsigned long folio_nr_pages = 1UL << ra->order; + fpin = maybe_unlock_mmap_for_io(vmf, fpin); - ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1); - ra->size = HPAGE_PMD_NR; + ractl._index &= ~(folio_nr_pages - 1); + ra->size = folio_nr_pages; /* - * Fetch two PMD folios, so we get the chance to actually + * Fetch two folios so we get the chance to actually * readahead, unless we've been told not to. */ if (!(vm_flags & VM_RAND_READ)) ra->size *= 2; - ra->async_size = HPAGE_PMD_NR; - ra->order = HPAGE_PMD_ORDER; + ra->async_size = folio_nr_pages; page_cache_ra_order(&ractl, ra); return fpin; } -- 2.52.0