From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7B344CD5BB0 for ; Fri, 22 May 2026 16:24:43 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4247A6B00BF; Fri, 22 May 2026 12:24:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2F44E6B00C3; Fri, 22 May 2026 12:24:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0D1EE6B00C4; Fri, 22 May 2026 12:24:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id DC4B36B00BF for ; Fri, 22 May 2026 12:24:41 -0400 (EDT) Received: from smtpin11.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id A920DA075F for ; Fri, 22 May 2026 16:24:41 +0000 (UTC) X-FDA: 84795579162.11.7D90D5B Received: from out-180.mta1.migadu.com (out-180.mta1.migadu.com [95.215.58.180]) by imf27.hostedemail.com (Postfix) with ESMTP id E914440003 for ; Fri, 22 May 2026 16:24:39 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=whYG6bQa; spf=pass (imf27.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.180 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1779467080; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=J35AS/PULwEysdWQSYhJZ0mNgY8vYVr+6J5F9KzoNSM=; b=08zHI9yWfA86kf5dHns38EvOcawnrQ5KEXITg09Xv4E6bbLUKoipVwjxQcmsZgM2lvCgGY pf9+oHoXMrtT/FRnZKh1scmtAH09IAmOcVsvT0w7vRTxjveBrXQ2KEjUxAdPH9QGVVnXP2 rlRdorbkgLaqsBclwTwqE3lAJxWX4Ek= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=whYG6bQa; spf=pass (imf27.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.180 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1779467080; a=rsa-sha256; cv=none; b=JchBKeUOZTkSJ46IZax9XMj7zclv0gZSgKAYSmGOq3kJu637iJHqDU3I9CFWAklhPpD4LN 7xlDHtxgr+jJJIOMiJEXRBM4Ki5q96HZ8DyfN8UPd80cywrE7JcmjzKl/CZGR2fqbKkJad L/CvkiGYy1oKmiE6/tOPelchfGFdIFA= 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=1779467078; 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=J35AS/PULwEysdWQSYhJZ0mNgY8vYVr+6J5F9KzoNSM=; b=whYG6bQaTpfWs6obTGhdUQR1ElLBtgqngR3UbASdTiAFG6Wc2nX87aMPGwETobOsX6f26C dexgRB/nobYzJ4JUsS2zdrsKlP+2GVKzSYZh9DwWs5Q2kPahX7eF9yZVdumz7mNxAQj7Nq mVVL62IK50Y4O6ziGDjKQYWhV4694iU= 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 1/2] mm: bypass mmap_miss heuristic for VM_EXEC readahead Date: Fri, 22 May 2026 09:23:47 -0700 Message-ID: <20260522162422.3856502-2-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-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E914440003 X-Stat-Signature: 586y83tg5nbjna5nxij4d9a4npttek54 X-HE-Tag: 1779467079-115258 X-HE-Meta: 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 xo8dR+3z C2tl8hyhWcWgu7z0A7N/chPRK8RVqzSrZfHxScuWYJWEqD+Kjcb1OgbD83jmFphcllw1d5dQXVSokN8yVSIe+AAb0OfrsoC5xd0lvC5tANLR5/Gi4JdplXeo7leC9ChQyrPO5UdswDr+nzaBZTK7R0AAWME6Mv7DoSmCbeweJNwkWAcgwYZR7y4qOMEAXXiRQ6DaPLs9cMzwNRpolPdNZcT1JO0EVDNof9lxcSj2HLJYo6IfcSorE+YXVjomKXYFpz1fojWvAbbRSrlyVtzDVOLgq65M2efPJ51bQnrfNqZT7+hz9wGytEaLNwhzZVE4W8xHcYB0+LwU6qM2ZgsKknSGD/eAJVS72Z3kkXnS2DcdFZZTJG1d3CM5LLtVEOSPKt3KnQa/mKnc3qZQwzFG1qgjkNMpagIJyT4qh Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The mmap_miss counter in do_sync_mmap_readahead() tracks whether readahead is useful for mmap'd file access. It is incremented by 1 on every page cache miss in do_sync_mmap_readahead(), and decremented in two places: - filemap_map_pages(): decremented by N for each of N pages successfully mapped via fault-around (pages found already in cache, evidence readahead was useful). Only pages not in the workingset count as hits. - do_async_mmap_readahead(): decremented by 1 when a page with PG_readahead is found in cache. When the counter exceeds MMAP_LOTSAMISS (100), all readahead is disabled, including the targeted VM_EXEC readahead [1] that requests large folio orders for contpte mapping. On arm64 with 64K base pages, both decrement paths are inactive: 1. filemap_map_pages() is never called because fault_around_pages (65536 >> PAGE_SHIFT = 1) disables should_fault_around(), which requires fault_around_pages > 1. With only 1 page in the fault-around window, there is nothing "around" to map. 2. do_async_mmap_readahead() never fires for exec mappings because exec readahead sets async_size = 0, so no PG_readahead markers are placed. With no decrements, mmap_miss monotonically increases past MMAP_LOTSAMISS after 100 page faults, disabling all subsequent exec readahead. Fix this by excluding VM_EXEC VMAs from the mmap_miss logic, similar to how VM_SEQ_READ is already excluded. The exec readahead path is targeted (one folio at the fault location, async_size=0), not speculative prefetch, so the mmap_miss heuristic designed to throttle wasteful speculative readahead should not apply to it. [1] https://lore.kernel.org/all/20250430145920.3748738-6-ryan.roberts@arm.com/ Signed-off-by: Usama Arif Reviewed-by: Jan Kara Reviewed-by: Kiryl Shutsemau (Meta) --- mm/filemap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 5aaba0d3e81d..f45a1b74870d 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3339,7 +3339,7 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) } } - if (!(vm_flags & VM_SEQ_READ)) { + if (!(vm_flags & (VM_SEQ_READ | VM_EXEC))) { /* Avoid banging the cache line if not needed */ mmap_miss = READ_ONCE(ra->mmap_miss); if (mmap_miss < MMAP_LOTSAMISS * 10) -- 2.52.0