From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) (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 39C3221CC7B for ; Thu, 12 Jun 2025 07:51:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749714720; cv=none; b=mwsyx4LzPFzFLpAUq88LTAN+dA5NH1Pnz3/W3OvjuBZ5WtGPw5C7QbTCJPsUMBAQFcl6Y7AMFLeDR7Ar2OfD1HCYRStYrHwcvnRIorvG2gHundYq1IKh4jUZ5Up8G/Z5sYtY+eiZhq5vgmvB/ub5MqAyitlVcuyP8aWN9ePziMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749714720; c=relaxed/simple; bh=2Kx5fLqRaKt/MgOfiMkH4x3gemqMdZHiq4JDXLEI0nA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=U1jxokPkCVFcsplf9ICN2AIxoE+7/tvn4rw73YjQ6/cgBT21oG0ICctnuHUO4psNAtjpzlcFNm5haxNBoKDy0WbSxngBwn4FJX5EhBm7nolAV+/sKqik4f0Hhj1ge8oC5NSvZtWCT90/W5RlTmfRR4Zj4UWLQ4ag1HCGYsFf0/0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=YxS0YGfB; arc=none smtp.client-ip=115.124.30.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="YxS0YGfB" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1749714709; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=aynmETi5QcvCc7hYrpbVi3vxwUCYZE5k+WSqXSsZ868=; b=YxS0YGfBgTGNeX1xzR2469i6EI1MLlHKl5lvuSMlK9nVFV/glu0c2Te5ZaS3UJiNQNb9yzvOJ4hcaxO13/m5rbv0vu5Yj2aDeZ47zjhwZYFk74YEQW78ydaW8gI0pzxBU2F3+Si8rQXAeYX0MrC6d6uT0Ob4+U1raXSm6zmgyjc= Received: from 30.74.144.123(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0Wdg73Zo_1749714707 cluster:ay36) by smtp.aliyun-inc.com; Thu, 12 Jun 2025 15:51:48 +0800 Message-ID: <2ff65f37-efa9-4e96-9cdf-534d63ff154e@linux.alibaba.com> Date: Thu, 12 Jun 2025 15:51:47 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] mm: huge_memory: disallow hugepages if the system-wide THP sysfs settings are disabled To: David Hildenbrand , akpm@linux-foundation.org, hughd@google.com Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <8eefb0809c598fadaa4a022634fba5689a4f3257.1749109709.git.baolin.wang@linux.alibaba.com> <1ec368c4-c4d8-41ea-b8a3-7d1fdb3ec358@redhat.com> From: Baolin Wang In-Reply-To: <1ec368c4-c4d8-41ea-b8a3-7d1fdb3ec358@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2025/6/11 20:34, David Hildenbrand wrote: > On 05.06.25 10:00, Baolin Wang wrote: >> The MADV_COLLAPSE will ignore the system-wide Anon THP sysfs settings, >> which >> means that even though we have disabled the Anon THP configuration, >> MADV_COLLAPSE >> will still attempt to collapse into a Anon THP. This violates the rule >> we have >> agreed upon: never means never. >> >> Another rule for madvise, referring to David's suggestion: “allowing >> for collapsing >> in a VM without VM_HUGEPAGE in the "madvise" mode would be fine". >> >> To address this issue, should check whether the Anon THP configuration >> is disabled >> in thp_vma_allowable_orders(), even when the TVA_ENFORCE_SYSFS flag is >> set. >> >> In summary, the current strategy is: >> >> 1. If always & orders == 0, and madvise & orders == 0, and >> hugepage_global_enabled() == false >> (global THP settings are not enabled), it means mTHP of that orders >> are prohibited >> from being used, then madvise_collapse() is forbidden for that orders. >> >> 2. If always & orders == 0, and madvise & orders == 0, and >> hugepage_global_enabled() == true >> (global THP settings are enabled), and inherit & orders == 0, it means >> mTHP of that >> orders are still prohibited from being used, thus madvise_collapse() >> is not allowed >> for that orders. >> >> Reviewed-by: Zi Yan >> Signed-off-by: Baolin Wang >> --- >>   include/linux/huge_mm.h | 23 +++++++++++++++++++---- >>   1 file changed, 19 insertions(+), 4 deletions(-) >> >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> index 2f190c90192d..199ddc9f04a1 100644 >> --- a/include/linux/huge_mm.h >> +++ b/include/linux/huge_mm.h >> @@ -287,20 +287,35 @@ unsigned long thp_vma_allowable_orders(struct >> vm_area_struct *vma, >>                          unsigned long orders) >>   { >>       /* Optimization to check if required orders are enabled early. */ >> -    if ((tva_flags & TVA_ENFORCE_SYSFS) && vma_is_anonymous(vma)) { >> -        unsigned long mask = READ_ONCE(huge_anon_orders_always); >> +    if (vma_is_anonymous(vma)) { >> +        unsigned long always = READ_ONCE(huge_anon_orders_always); >> +        unsigned long madvise = READ_ONCE(huge_anon_orders_madvise); >> +        unsigned long inherit = READ_ONCE(huge_anon_orders_inherit); >> +        unsigned long mask = always | madvise; >> + >> +        /* >> +         * If the system-wide THP/mTHP sysfs settings are disabled, >> +         * then we should never allow hugepages. > > +         */> +        if (!(mask & orders) && > !(hugepage_global_enabled() && (inherit & orders))) >> +            return 0; > > I'm still trying to digest that. Isn't there a way for us to work with > the orders, > essentially masking off all orders that are forbidden globally. Similar > to below, if !orders, then return 0? > /* Orders disabled directly. */ > orders &= ~TODO; > /* Orders disabled by inheriting from the global toggle. */ > if (!hugepage_global_enabled()) >     orders &= ~READ_ONCE(huge_anon_orders_inherit); > > TODO is probably a -1ULL and then clearing always/madvise/inherit. Could > add a simple helper for that > > huge_anon_orders_never I followed Lorenzo's suggestion to simplify the logic. Does that look more readable? diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 2f190c90192d..3087ac7631e0 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -265,6 +265,43 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, unsigned long tva_flags, unsigned long orders); +/* Strictly mask requested anonymous orders according to sysfs settings. */ +static inline unsigned long __thp_mask_anon_orders(unsigned long vm_flags, + unsigned long tva_flags, unsigned long orders) +{ + unsigned long always = READ_ONCE(huge_anon_orders_always); + unsigned long madvise = READ_ONCE(huge_anon_orders_madvise); + unsigned long inherit = READ_ONCE(huge_anon_orders_inherit); + bool inherit_enabled = hugepage_global_enabled(); + bool has_madvise = vm_flags & VM_HUGEPAGE; + unsigned long mask = always | madvise; + + mask = always | madvise; + if (inherit_enabled) + mask |= inherit; + + /* All set to/inherit NEVER - never means never globally, abort. */ + if (!(mask & orders)) + return 0; + + /* + * Otherwise, we only enforce sysfs settings if asked. In addition, + * if the user sets a sysfs mode of madvise and if TVA_ENFORCE_SYSFS + * is not set, we don't bother checking whether the VMA has VM_HUGEPAGE + * set. + */ + if (!(tva_flags & TVA_ENFORCE_SYSFS)) + return orders; + + mask = always; + if (has_madvise) + mask |= madvise; + if (hugepage_global_always() || (has_madvise && inherit_enabled)) + mask |= inherit; + + return orders & mask; +} + /** * thp_vma_allowable_orders - determine hugepage orders that are allowed for vma * @vma: the vm area to check @@ -287,19 +324,8 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma, unsigned long orders) { /* Optimization to check if required orders are enabled early. */ - if ((tva_flags & TVA_ENFORCE_SYSFS) && vma_is_anonymous(vma)) { - unsigned long mask = READ_ONCE(huge_anon_orders_always); - - if (vm_flags & VM_HUGEPAGE) - mask |= READ_ONCE(huge_anon_orders_madvise); - if (hugepage_global_always() || - ((vm_flags & VM_HUGEPAGE) && hugepage_global_enabled())) - mask |= READ_ONCE(huge_anon_orders_inherit); - - orders &= mask; - if (!orders) - return 0; - } + if (vma_is_anonymous(vma)) + orders = __thp_mask_anon_orders(vm_flags, tva_flags, orders); return __thp_vma_allowable_orders(vma, vm_flags, tva_flags, orders); }