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 4FFE6CD6E6E for ; Thu, 4 Jun 2026 19:30:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 66D5F6B0088; Thu, 4 Jun 2026 15:30:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5F73D6B008C; Thu, 4 Jun 2026 15:30:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 30ECB6B0088; Thu, 4 Jun 2026 15:30:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 1A7186B0088 for ; Thu, 4 Jun 2026 15:30:55 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id D4BC71621D0 for ; Thu, 4 Jun 2026 19:30:54 +0000 (UTC) X-FDA: 84843222828.04.B0A6F98 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) by imf28.hostedemail.com (Postfix) with ESMTP id D64D8C000C for ; Thu, 4 Jun 2026 19:30:52 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=suse.de header.s=susede2_rsa header.b="ObOC8E/s"; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=xX4TZ1Ou; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=B49iZUXG; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=AnHU30aD; spf=pass (imf28.hostedemail.com: domain of pfalcato@suse.de designates 195.135.223.130 as permitted sender) smtp.mailfrom=pfalcato@suse.de; dmarc=pass (policy=none) header.from=suse.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1780601453; 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-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qUhs7nHrVwVahKP19CONWmvueVUZvVfuS2bIUip09cI=; b=LGqXUCiiUjz+42u49eZEoACtNEGQo51bqnWWxdJaD15ugiTPk3WyqtEwo4G2gP0vLi8fo7 6A7C8kXXtSGVIFMo7gmYwQXX8MyaQw+LXecAgRKvZodyURI8hYBRC7F6OlM/vUWjEn6u+H 6vMNmwitfGcc44i0opp3xDPZABxw+vI= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1780601453; b=SdPFGo4nwCLYgUVUm8BenbmdjhpJruUOr7alYlFjG7Q+Plce/keW/dJNhI986ow09h60WF 1XCML7/turMfXdfOKkKjjCb6BbTQSUsohYg4hG/XFxueRMoCUd7iaTvSh0bbmYUQH31MSS UWz+7NDwWolrP2/vWDWTlMspI/1ybMw= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=suse.de header.s=susede2_rsa header.b="ObOC8E/s"; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=xX4TZ1Ou; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=B49iZUXG; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=AnHU30aD; spf=pass (imf28.hostedemail.com: domain of pfalcato@suse.de designates 195.135.223.130 as permitted sender) smtp.mailfrom=pfalcato@suse.de; dmarc=pass (policy=none) header.from=suse.de Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 464576B059; Thu, 4 Jun 2026 19:30:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1780601451; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qUhs7nHrVwVahKP19CONWmvueVUZvVfuS2bIUip09cI=; b=ObOC8E/s242xs8rtpTwzGe9x012+MvEF7x7lQ/QR6XNWcecL57OHhrtEeWyPsgfJtouwRm r/n42gf9UvuYj4IifaJnQeipfVgy1n/hZ7i61vVz/u7Txos8K5VRPBinNolwzswD7pdZGP YpDCiqRQZOTcXzEL4wHJ8e8d2EVsuuY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1780601451; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qUhs7nHrVwVahKP19CONWmvueVUZvVfuS2bIUip09cI=; b=xX4TZ1OuGwffZQhiUWMU1DTM3tnSvWvkm1rBX7PCU4Q8hfRmnKjirqbGaF1vpkFnnuitz4 nO+jU2qDW+3uXKAg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1780601450; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qUhs7nHrVwVahKP19CONWmvueVUZvVfuS2bIUip09cI=; b=B49iZUXGW6b652AdBBs53WABYQQo1Bm8iuEVubc5CLhv/8Ln12qK/PewKxT3ks07cc4uF+ XO0AKg+pBd4kdBET20ErmxBMU28d3CblKOW3xFJQyhz59r2RADADOBIwfdUVluvGoa+XfU 3Ij6F6sgc5OJmnmrbkVt5HNnc8J8sgI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1780601450; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qUhs7nHrVwVahKP19CONWmvueVUZvVfuS2bIUip09cI=; b=AnHU30aDHDytjj8TvaarlGVKqeukhTSpUIVKkDU05ex2/Yq+QWZvQ9FwxAjxVaum5/Ln85 xVYzWQntN/Jy31Bg== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id F15B1779A8; Thu, 4 Jun 2026 19:30:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id w/EYD2XSIWpsEQAAD6G6ig (envelope-from ); Thu, 04 Jun 2026 19:30:45 +0000 Date: Thu, 4 Jun 2026 20:30:43 +0100 From: Pedro Falcato To: Usama Arif Cc: Andrew Morton , david@kernel.org, willy@infradead.org, ryan.roberts@arm.com, linux-mm@kvack.org, 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 , ziy@nvidia.com, hannes@cmpxchg.org, kas@kernel.org, shakeel.butt@linux.dev, kernel-team@meta.com Subject: Re: [PATCH v7 1/2] mm: bypass mmap_miss heuristic for VM_EXEC readahead Message-ID: References: <20260601102205.3985788-1-usama.arif@linux.dev> <20260601102205.3985788-2-usama.arif@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260601102205.3985788-2-usama.arif@linux.dev> X-Rspamd-Queue-Id: D64D8C000C X-Rspam-User: X-Stat-Signature: w1rcko3cpm5z6ee3omnxeujpt1wuw7k7 X-Rspamd-Server: rspam08 X-HE-Tag: 1780601452-795091 X-HE-Meta: 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 YK667vYZ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jun 01, 2026 at 03:21:17AM -0700, Usama Arif wrote: > The mmap_miss heuristic is intended to stop speculative mmap readahead > when a file looks like a random-access workload. That does not fit the > VM_EXEC path very well. > > VM_EXEC readahead is already constrained differently from ordinary mmap > read-around: it is bounded by the VMA, uses exec_folio_order() to choose > an order useful for executable mappings, and sets async_size to 0 so it > does not create follow-on readahead. When VM_HUGEPAGE is also present, > the larger readahead is an explicit userspace opt-in. > > The mmap_miss counter is decremented from cache-hit paths in > do_async_mmap_readahead() and filemap_map_pages(). Those paths are not > always enough to balance the synchronous miss increments for executable > mappings. In particular, when fault-around is effectively disabled, such > as configurations where fault_around_pages is 1, filemap_map_pages() is > not reached from the fault path. The counter can then become a stale > throttle for VM_EXEC mappings and suppress the readahead behavior that > the executable-specific path is trying to provide. > > Skip both mmap_miss increments and decrements for VM_EXEC mappings, > matching the existing VM_SEQ_READ treatment and keeping the counter > accounting symmetric. > > Signed-off-by: Usama Arif > Reviewed-by: Jan Kara > Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: Pedro Falcato > --- > mm/filemap.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index cca20e350c95..a16b33e0fc71 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))) { Just a side comment: I really hate these adhoc criteria all around filemap/readahead. One day we ought to actually write things down, and write things in a way that isn't entirely mysterious. I might see if I send a patch for this down the line... > /* Avoid banging the cache line if not needed */ > mmap_miss = READ_ONCE(ra->mmap_miss); > if (mmap_miss < MMAP_LOTSAMISS * 10) > @@ -3434,12 +3434,12 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, > * times for a single folio and break the balance with mmap_miss > * increase in do_sync_mmap_readahead(). > * > - * VM_SEQ_READ mappings skip the mmap_miss increment in > + * VM_SEQ_READ and VM_EXEC mappings skip the mmap_miss increment in > * do_sync_mmap_readahead(), so skip the decrement here as well to > * keep the counter symmetric. > */ > if (likely(!folio_test_locked(folio)) && > - !(vmf->vma->vm_flags & VM_SEQ_READ)) { > + !(vmf->vma->vm_flags & (VM_SEQ_READ | VM_EXEC))) { > mmap_miss = READ_ONCE(ra->mmap_miss); > if (mmap_miss) > WRITE_ONCE(ra->mmap_miss, --mmap_miss); > @@ -3941,14 +3941,14 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, > * Don't decrease mmap_miss in this scenario to make sure > * we can stop read-ahead. > * > - * VM_SEQ_READ mappings skip the mmap_miss increment in > - * do_sync_mmap_readahead(), so skip the decrement here as > - * well to keep the counter symmetric. > + * VM_SEQ_READ and VM_EXEC mappings skip the mmap_miss > + * increment in do_sync_mmap_readahead(), so skip the > + * decrement here as well to keep the counter symmetric. > */ > if ((map_ret & VM_FAULT_NOPAGE) && > !(vmf->flags & FAULT_FLAG_TRIED) && > !folio_test_workingset(folio) && > - !(vma->vm_flags & VM_SEQ_READ)) { > + !(vma->vm_flags & (VM_SEQ_READ | VM_EXEC))) { > unsigned short mmap_miss; > > mmap_miss = READ_ONCE(file->f_ra.mmap_miss); > -- > 2.52.0 > -- Pedro