From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 37D24346E7F for ; Fri, 22 May 2026 16:24:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779467088; cv=none; b=LuabkGxnpgnOz/4z3MIyaChdn0Bk1gG6ebGZNpL2evh/lIK/AIrutJNERKbaSf4s2aRL2vcB0jY1Emg4WS01jYXUQL0RwRiLiS5/WNlHd7YH5Tb7Q2Aw+iuSPrnanIQcTMt5Ce2hoIvXGdxO2bOUICdHhcTvs+eCt/wg/UajC8U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779467088; c=relaxed/simple; bh=ENFdwFzwYK4H1Gi0MXb2MaLiq1k0TD1SbF6GrUxaDpc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GZJYwvSdvhWQNHevjEXI59issCyAxHKRJ60M7q6fQx/snPN9WSkvi0JGeAp8bTZ8uebkzqA5bK8425gPg/rpzHgVjvrCC8Tzl426V2V/9A2/yVRdoiCOPvLk1uVcOEEpJ7sWpCp295YNHwyWG/Gaxv0OzecSjSDerZK/RFQNjYw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=ibg5Vx7A; arc=none smtp.client-ip=95.215.58.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="ibg5Vx7A" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. 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, 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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