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[70.27.3.10]) by smtp.gmail.com with ESMTPSA id x3-20020a056602160300b0067a338211b3sm3640051iow.3.2022.08.11.08.19.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Aug 2022 08:19:36 -0700 (PDT) Date: Thu, 11 Aug 2022 11:19:35 -0400 From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Minchan Kim , David Hildenbrand , Nadav Amit , Andrew Morton , Hugh Dickins , Vlastimil Babka , Andrea Arcangeli , Andi Kleen , Huang Ying , "Kirill A . Shutemov" Subject: Re: [PATCH v3 5/7] mm: Remember young/dirty bit for page migrations Message-ID: References: <20220809220100.20033-1-peterx@redhat.com> <20220809220100.20033-6-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: <20220809220100.20033-6-peterx@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660231180; 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=VvBOzAkTVuIJDSaHKsvqxSvSouuZ1MXSA9Vu1AJkje8=; b=MATpKvkFeVIPXevSFNQMqyOuwt6lTVwC0fpjHsbdAKs6+hgrEb8Ntc+KB0tAzu23ZO7zAf DatZnzVdKjJF2iRunxSjFnSwXTzY8al+jKyZer7lTVjqTD7N9k4f4YP04/rSESP4v6wBe4 HcXFiAHhYfcMy5sAmuoj17BPmdfe778= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=TM0Pkf4x; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf23.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660231180; a=rsa-sha256; cv=none; b=CX/DKB/m/LvHFE6EtjTsxHgd7kNvSGgyJErkhvSu388rtqOvbbeSVknGMI21/Lj9dpyl3n uFrZ6TBW5OUCKsucZVW4qjLb3M+isKCwhEqC9rytwFCOhxlERK4PTlnFIvpwz3vT0P3faL m//2Rn/AsxWstBDQeclm+4AnKz3IOeM= X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 1A989140170 X-Rspam-User: X-Stat-Signature: 6zsqqz1pt6p8hwcgqnuhaamcrzyu688p Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=TM0Pkf4x; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf23.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com X-HE-Tag: 1660231179-826441 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 09, 2022 at 06:00:58PM -0400, Peter Xu wrote: > diff --git a/mm/migrate_device.c b/mm/migrate_device.c > index 27fb37d65476..699f821b8443 100644 > --- a/mm/migrate_device.c > +++ b/mm/migrate_device.c > @@ -221,6 +221,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > else > entry = make_readable_migration_entry( > page_to_pfn(page)); > + if (pte_young(pte)) > + entry = make_migration_entry_young(entry); > + if (pte_dirty(pte)) > + entry = make_migration_entry_dirty(entry); > swp_pte = swp_entry_to_pte(entry); > if (pte_present(pte)) { > if (pte_soft_dirty(pte)) This change needs to be wrapped with pte_present() at least.. I also just noticed that this change probably won't help anyway because: (1) When ram->device, the pte will finally be replaced with a device private entry, and device private entry does not yet support A/D, it means A/D will be dropped again, (2) When device->ram, we are missing information on either A/D bits, or even if device private entries start to suport A/D, it's still not clear whether we should take device read/write into considerations too on the page A/D bits to be accurate. I think I'll probably keep the code there for completeness, but I think it won't really help much until more things are done. -- Peter Xu