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]) by smtp.lore.kernel.org (Postfix) with ESMTP id EEFB9C6FD1D for ; Wed, 15 Mar 2023 03:33:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 528898E0001; Tue, 14 Mar 2023 23:33:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4D8E46B0074; Tue, 14 Mar 2023 23:33:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 39FD78E0001; Tue, 14 Mar 2023 23:33:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 2AE3D6B0072 for ; Tue, 14 Mar 2023 23:33:31 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id F4209C0E54 for ; Wed, 15 Mar 2023 03:33:30 +0000 (UTC) X-FDA: 80569712580.14.B86CE81 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf15.hostedemail.com (Postfix) with ESMTP id 9BDE5A000B for ; Wed, 15 Mar 2023 03:33:28 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iSRnfi1d; spf=pass (imf15.hostedemail.com: domain of longman@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1678851209; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=TbwJgOTQEBOTQga1KdTR+fInJ3Zcev0Mf+xVWLD7VKE=; b=pk9RqyIPCoNgjA5vruBGsXt29uHL0kh6M4rqWCDS3201cNtDakXW5DVFmnQp2bnLEyhFmO iN9UoDK8v/9Ak2gC3m0QXcldCM2gawGpm2pQruwsmLrtsJYyOwfAQN7xBtGhzekQ+cBPcQ T2DLlhq8i7nnt2Msn7h4vaociw7Xw9o= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iSRnfi1d; spf=pass (imf15.hostedemail.com: domain of longman@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1678851209; a=rsa-sha256; cv=none; b=KJ00KbyEAHaGyFcrj5m3uVgoRYhS50YPE7TPW603jhGxbJHtYTpn3VMvR6lYr4ngNaApGY VOWQP1+ydHbfaSRuAOjiS9JtIhyIb5pH85lDpCtGcJ/5LJUSVOsTuwvVU1WqNRnzSDbYdM IAYA/9s6Xo8rTMmXWhk2JGzq/aiGCi4= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1678851207; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TbwJgOTQEBOTQga1KdTR+fInJ3Zcev0Mf+xVWLD7VKE=; b=iSRnfi1dbAqJ+vDsPC1j0pCDufhazCj8wCKnzbx797iGdJ+5j4EQt1to97myPF0lU2RQdu Fvm55+TkeTB2JiSXA9eYYvWViQrrKyAqrMjhXLUVFG0Ccit5GXxZ09dXou/O0+PDnzWlK7 +VfeTV836oqgNUvDl8N1HIN8MjTqSo4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-539-l7C_wICLOjC5hbBTZp-EPA-1; Tue, 14 Mar 2023 23:33:25 -0400 X-MC-Unique: l7C_wICLOjC5hbBTZp-EPA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 77CDC101AA78; Wed, 15 Mar 2023 03:33:24 +0000 (UTC) Received: from [10.22.9.226] (unknown [10.22.9.226]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4A38E40C6E6A; Wed, 15 Mar 2023 03:33:16 +0000 (UTC) Message-ID: <84d8fd38-f05c-73f5-ef50-fcac524097f3@redhat.com> Date: Tue, 14 Mar 2023 23:33:07 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH] memcg: page_cgroup_ino() get memcg from compound_head(page) Content-Language: en-US To: Yosry Ahmed Cc: Andrew Morton , Hugh Dickins , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Naoya Horiguchi , Miaohe Lin , Vladimir Davydov , linux-mm@kvack.org, cgroups@vger.kernel.org, Matthew Wilcox References: <20230313083452.1319968-1-yosryahmed@google.com> <20230313124431.fe901d79bc8c7dc96582539c@linux-foundation.org> <61e8e6d3-697e-f9a5-a1fb-45a3448ee5db@redhat.com> From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9BDE5A000B X-Stat-Signature: bf5xbdshjfo9ux6u53kac4spzxzxm9be X-HE-Tag: 1678851208-897656 X-HE-Meta: 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 T0APcsSc ZHYYipGD1TEs0iZ03n8Iggtrvv03WQinM45bamRzhZxbdJtx9PtUGausJaxW4ihhTDY6tAnjfWwycuHtlb24kGeVPjuuvVlx+3+tOa4WVmNRa8o7hV5d9DgpYDPaJKdyZFzNDYkLFd8YcqRbvfisHpoYjhJZ65qETE29rDqQQeW21CNPQTLTVc02ISjdOArbUSeKMCeqVMrm5jIQgS4171sz7T9JEzOhQIrQD1QGgoc/okzcFUausrmxPdEznpD2QpwYoEEfX3OtEpsdIVeYIXSKKtfkt2N4EH6qdMMWbgDI62iw= 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 3/14/23 23:10, Yosry Ahmed wrote: >>> The only other user today is print_page_owner_memcg(). I am not sure >>> if it's doing the right thing by explicitly reading page->memcg_data, >>> but it is already excluding pages that have page->memcg_data == 0, >>> which should be the case for tail pages. >> It is reading memcg_data directly to see if it is slab cache page. It is >> currently skipping page that does not have memcg_data set. > IIUC this skips tail pages, because they should always have > page->memcg_data == 0, even if they are charged to a memcg. To > correctly get their memcg we should read it from the > compound_head()/page_folio(). The purpose of that function is mainly to report pages that have a reference to a memcg, especially the dead one. So by counting the occurrence of a particular cgroup name, we can have a rough idea of that. So only head page has relevance here and we can skip the tail pages. > > My 2c, we can check PageSlab() to print the extra message for slab > pages, instead of reading memcg_data directly, which kinda breaks the > abstraction created by the various helpers for reading a page memcg. > Someone can easily change something in how memcg_data is interpreted > in those helpers without realizing that page_owner is also reading it. You are right. We should be using a helper if available. I will send a patch to fix that. Thanks, Longman