From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f49.google.com (mail-wm1-f49.google.com [209.85.128.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D20A4BE6C for ; Wed, 30 Jul 2025 22:24:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.49 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753914282; cv=none; b=famWPblF6RA/w4N0jB57CdHFfiFE1iPetxpOs6AHqxaAYWlgogczT8LiehefFQbD8EufSvw3CxHz+fbc5cEfAqAw4tRHMCpfRrxVw7ZN/sW6fS7Ls1RCqlDVVFwEobXU4uT9uHRmx15Te7Kg9sdFUrOVL6MIh+N1zKyvrw+m6A8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753914282; c=relaxed/simple; bh=EX1pUNxp1hbod6lA6ki6m6Q9fp/HW28UG7wPzYiWJ7M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=e09Hp6TS+4pH6NEb9MpOk2satMJj0vM3ZYhnFuRM3GERCF661lFY/4LSYXx+7ZWIlP/Sg4cQmMk6g30aEgsNkRfPI1sdYJBF8A2+CJVKOIfE9moO/vUqD0+ERcL2kC/HJUYey8hM6PrurBrfoJukhsoOW7hS0pUCq+58U8NR34g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=blTpLiml; arc=none smtp.client-ip=209.85.128.49 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="blTpLiml" Received: by mail-wm1-f49.google.com with SMTP id 5b1f17b1804b1-4561607166aso2024135e9.2 for ; Wed, 30 Jul 2025 15:24:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1753914279; x=1754519079; darn=lists.linux.dev; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=OCbT9/cz+rXGQ8ARnOwy7QkIK/KpaHmQmlR+7AOK0Pc=; b=blTpLimlSVEMCV/NraKbgYt4gDPY+ECEMIX2JzIO/NpAoqHz0BqryoQ3P8vRx2nvfh KqE2xjRNbtR3mUE9jj2IdFnhcaIQ/9uMDRXJ+JrbKuTr1fB/iyblk1obJGqTe/z0nVCK 4xid9bDTdb49Z4mhJ21Ad0biyQdxtFGk2SKc1jmOuFblNUo3/aWIAHXQOKIYevMXKu8u I55kH0yBTILEbvep3StP2kAiyotwb75VugKZWR/8twcSUi1Xiwn6D2hQDdFJ6jZAg8a9 qRZJMYLZ28wICOh0BXENEx37HNqVfmU98p4V7ArdPIY6OXJL6GQeM3sa36V1oeJVrcOL zsIQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1753914279; x=1754519079; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=OCbT9/cz+rXGQ8ARnOwy7QkIK/KpaHmQmlR+7AOK0Pc=; b=XIhJyjuMFK6I3P0/mdTKrFt5troHt8A6jJGDDyMLB57j1/BGftW9LpO1dAPlDEy4gH IKMn8pPHb0q1W5/Hsm6dJ6h758hHdrs7ZKenx1w+rcNm4rUbcwQNnZ1fbQc0VyvH9+St yldDO18B9h8vKl4sYNAqqRpxd/TqRCPZLlH19Xr935lmk0YBAKaKPH6J3btIcsYb0UuW G4eRGui0s17QilQBMKfLIcvqXr99waZeQQ2WGYp4nQUtcwWvRBrXBCQD0fXEcGMgqoYR OYM0I1qKB/36th/9LBvb5WNo4zpO9CJqmjpSC2jO3YpnRCnoFb+LdmzuqJQIP31qa5YE Ed0w== X-Forwarded-Encrypted: i=1; AJvYcCVmhyJAZ/fNpEfazS0FE4FL5zLL0KHYNynOY5QMewLQ7JVgzY5tXtkJ61CTEyrWIpuEHLWjVg==@lists.linux.dev X-Gm-Message-State: AOJu0Yxivrx/g8R0mscg3wyU8n72IacS+9vxnHyYvrH28q+9eXi/Cq2U gBRvbBlcooSuGWuVEfJ/10VfPMj2AT9h2VKUkCalTvXB0MNjrxBC9K9M X-Gm-Gg: ASbGnct0jlH+53bkAk70qoNEiNMuZP+R2LMlT7z/7Vhf+/YBRWxKTfeFoRArI6NXzgv YoTHum8oqiU70SO1q/WjDC9NNomr9971IJDoLC7JVVX02WHHyfeJs4hAdnHoWnTJn7smEcCY9W1 AnkG98NytVPRzVmSmj4ly5nprwzpD4XiaNEVJ4CmNxeHSTabWS2t7rCWIFIbm5A7MXpw2Mvjr3l heiJI6m6n6a2MIF4ORtSeSh59wO9yjyvxVopEsAhMrylZLNa5WEllNiGshglgYB56vu84b+i55W QsHZkI1qRTO7cxmSv3Y5rRXKbNYUO2fu30nJgu4LCg9Tt8EuVXWcbgcQJJQ9AlSV5Ti5gWVtmUp EGMA6/lSkgmK/u/Ko1zufXeqZmzBLL2XreiOXGw== X-Google-Smtp-Source: AGHT+IEHwJ0OF/CEB1lfb4+OzjypEm8jkKSqIIDGkUMeRFWaULpe2YCUA7fNQcqZpUUGznElVR0FJg== X-Received: by 2002:a05:600c:4fd3:b0:453:697:6f08 with SMTP id 5b1f17b1804b1-45892bd1a95mr42393275e9.26.1753914278856; Wed, 30 Jul 2025 15:24:38 -0700 (PDT) Received: from devbig569.cln6.facebook.com ([2a03:2880:31ff:3::]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-458953f8e0dsm41450315e9.31.2025.07.30.15.24.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Jul 2025 15:24:38 -0700 (PDT) Date: Wed, 30 Jul 2025 15:24:36 -0700 From: Yueyang Pan To: David Hildenbrand Cc: SeongJae Park , Andrew Morton , Usama Arif , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 2/2] mm/damon: Add damos_stat support for vaddr Message-ID: References: <44a30f700fdcf4470318ef5cd248ba98c59b77a2.1753794408.git.pyyjason@gmail.com> <0cb3d5a5-683b-4dba-90a8-b45ab83eec53@redhat.com> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0cb3d5a5-683b-4dba-90a8-b45ab83eec53@redhat.com> On Tue, Jul 29, 2025 at 04:11:32PM +0200, David Hildenbrand wrote: > On 29.07.25 15:53, Yueyang Pan wrote: > > From: PanJason > > > > This patch adds support for damos_stat in virtual address space. > > It leverages the walk_page_range to walk the page table and gets > > the folio from page table. The last folio scanned is stored in > > damos->last_applied to prevent double counting. > > --- > > mm/damon/vaddr.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++- > > 1 file changed, 112 insertions(+), 1 deletion(-) > > > > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c > > index 87e825349bdf..3e319b51cfd4 100644 > > --- a/mm/damon/vaddr.c > > +++ b/mm/damon/vaddr.c > > @@ -890,6 +890,117 @@ static unsigned long damos_va_migrate(struct damon_target *target, > > return applied * PAGE_SIZE; > > } > > +struct damos_va_stat_private { > > + struct damos *scheme; > > + unsigned long *sz_filter_passed; > > +}; > > + > > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > > +static int damos_va_stat_pmd_entry(pmd_t *pmd, unsigned long addr, > > + unsigned long next, struct mm_walk *walk) > > +{ > > + struct damos_va_stat_private *priv = walk->private; > > + struct damos *s = priv->scheme; > > + unsigned long *sz_filter_passed = priv->sz_filter_passed; > > + struct folio *folio; > > + spinlock_t *ptl; > > + pmd_t pmde; > > + > > + ptl = pmd_lock(walk->mm, pmd); > > + pmde = pmdp_get(pmd); > > + > > + if (!pmd_present(pmde) || !pmd_trans_huge(pmde)) > > + goto unlock; > > + > > + /* Tell page walk code to not split the PMD */ > > + walk->action = ACTION_CONTINUE; > > + > > + folio = damon_get_folio(pmd_pfn(pmde)); > > + if (!folio) > > + goto unlock; > > + > > + if (damon_invalid_damos_folio(folio, s)) > > + goto update_last_applied; > > + > > + if (!damos_va_filter_out(s, folio, walk->vma, addr, NULL, pmd)){ > > + *sz_filter_passed += folio_size(folio); > > See my comment below regarding vm_normal_page and folio references. > > But this split into two handlers is fairly odd. Usually we only have a > pmd_entry callback (see madvise_cold_or_pageout_pte_range as an example), > and handle !CONFIG_TRANSPARENT_HUGEPAGE in there. > > Then, there is also no need to mess with ACTION_CONTINUE > Hi David. Thanks for your comment. I was not aware of the convention so I followed the existing code. I had a discussion with SJ today and in the next version I will change this by combining *pmd_entry() and *pte_entry(). We will also format the existing code in future patches. > > + } > > + > > + folio_put(folio); > > +update_last_applied: > > + s->last_applied = folio; > > +unlock: > > + spin_unlock(ptl); > > + return 0; > > +} > > +#else > > +#define damon_va_stat_pmd_entry NULL > > +#endif > > + > > +static int damos_va_stat_pte_entry(pte_t *pte, unsigned long addr, > > + unsigned long next, struct mm_walk *walk) > > +{ > > + struct damos_va_stat_private *priv = walk->private; > > + struct damos *s = priv->scheme; > > + unsigned long *sz_filter_passed = priv->sz_filter_passed; > > + struct folio *folio; > > + pte_t ptent; > > + > > + ptent = ptep_get(pte); > > + if (pte_none(ptent) || !pte_present(ptent)) > > + return 0; > > + > > + folio = damon_get_folio(pte_pfn(ptent)); > > + if (!folio) > > + return 0; > > We have vm_normal_folio() and friends for a reason -- so you don't have to > do pte_pfn() manually. > > ... and now I am confused. We are holding the PTL, so why would you have to > grab+put a folio reference here *at all*. > Thanks for pointing out. I thought someone could still change the folio and realized it could not happen with PTL. I will use vm_normal_folio* in the next version. > -- > Cheers, > > David / dhildenb >