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24 Oct 2022 20:22:15 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10510"; a="806521274" X-IronPort-AV: E=Sophos;i="5.95,210,1661842800"; d="scan'208";a="806521274" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Oct 2022 20:22:13 -0700 From: "Huang, Ying" To: Cc: , , , , Subject: Re: [PATCH v4 1/3] mm: add thp_utilization metrics to debugfs References: <6ee57dc7d2eadaee2816ef19fdbdc54ab356d5fb.1666150565.git.alexlzhu@fb.com> Date: Tue, 25 Oct 2022 11:21:33 +0800 In-Reply-To: <6ee57dc7d2eadaee2816ef19fdbdc54ab356d5fb.1666150565.git.alexlzhu@fb.com> (alexlzhu@fb.com's message of "Tue, 18 Oct 2022 20:42:18 -0700") Message-ID: <87mt9klhaa.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; 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dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=MrfTTlW0; spf=pass (imf29.hostedemail.com: domain of ying.huang@intel.com designates 192.55.52.43 as permitted sender) smtp.mailfrom=ying.huang@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Stat-Signature: x3kq93i3goiiwerwqn5rrcmd5futccs3 X-Rspamd-Queue-Id: 0D46D120014 X-Rspamd-Server: rspam07 X-Rspam-User: X-HE-Tag: 1666668136-394102 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: writes: [snip] > +static void thp_util_scan(unsigned long pfn_end) > +{ > + struct page *page = NULL; > + int bucket, current_pfn, num_utilized_pages; > + int i; > + /* > + * Scan through each memory zone in chunks of THP_UTIL_SCAN_SIZE > + * PFNs every second looking for anonymous THPs. > + */ > + for (i = 0; i < THP_UTIL_SCAN_SIZE; i++) { > + current_pfn = thp_scan.pfn; > + thp_scan.pfn += HPAGE_PMD_NR; > + if (current_pfn >= pfn_end) > + return; > + > + page = pfn_to_online_page(current_pfn); > + if (!page) > + continue; If my understanding were correct, the page may be offlined during pfn_to_online_page() and the following code. So we need to call get/put_online_mems(). If my understanding were incorrect, can anyone teach me on this? > + > + num_utilized_pages = thp_number_utilized_pages(page_folio(page)); > + bucket = thp_utilization_bucket(num_utilized_pages); > + if (bucket < 0) > + continue; > + > + thp_scan.buckets[bucket].nr_thps++; > + thp_scan.buckets[bucket].nr_zero_pages += (HPAGE_PMD_NR - num_utilized_pages); > + } > +} > + Best Regards, Huang, Ying