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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1580ECAAA2 for ; Thu, 25 Aug 2022 21:31:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232542AbiHYVbN (ORCPT ); Thu, 25 Aug 2022 17:31:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242770AbiHYVbJ (ORCPT ); Thu, 25 Aug 2022 17:31:09 -0400 Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com [67.231.153.30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 38E7EBD098 for ; Thu, 25 Aug 2022 14:31:04 -0700 (PDT) Received: from pps.filterd (m0148460.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 27PGTSe4005807 for ; Thu, 25 Aug 2022 14:31:03 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=facebook; bh=uien9I9/yhH00YAFVEobmw25WG+SJWjbrVulEVTverU=; b=Dkt7hI8aIBVy/JYVx3xACW0zEof75KS3MZZQhQIYQ3EswSFWMXy+g+CoXuZDPQi2a8GP Z8LIx1pLYalEOmpkmy2RsCsMCUgFUfLaKKwXfg4tKp7DGYP/snxeDmCNZh4NqwS4ba/x UnDlq8+JjNhotMRKHe/2nnqNESxepcYjbqQ= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3j5u5785gu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 25 Aug 2022 14:31:03 -0700 Received: from twshared22413.18.frc3.facebook.com (2620:10d:c085:108::4) by mail.thefacebook.com (2620:10d:c085:21d::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Thu, 25 Aug 2022 14:31:01 -0700 Received: by devvm6390.atn0.facebook.com (Postfix, from userid 352741) id 093D02DC95F6; Thu, 25 Aug 2022 14:30:57 -0700 (PDT) From: To: CC: , , , , , , Alexander Zhu Subject: [RFC 0/3] THP Shrinker Date: Thu, 25 Aug 2022 14:30:51 -0700 Message-ID: X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-GUID: 2gGg-llaj7bS_V_FyWCGeZUM_l_XlDJM X-Proofpoint-ORIG-GUID: 2gGg-llaj7bS_V_FyWCGeZUM_l_XlDJM X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-08-25_10,2022-08-25_01,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexander Zhu Transparent Hugepages use a larger page size of 2MB in comparison to normal sized pages that are 4kb. A larger page size allows for fewer TLB cache misses and thus more efficient use of the CPU. Using a larger page size also results in more memory waste, which can hurt performance in som= e use cases. THPs are currently enabled in the Linux Kernel by applications in limited virtual address ranges via the madvise system call. The THP shrinker tries to find a balance between increased use of THPs, and increased use of memory. It shrinks the size of memory by removing the underutilized THPs that are identified by the thp_utilization scanner.=20 In our experiments we have noticed that the least utilized THPs are almos= t entirely unutilized. Sample Output:=20 Utilized[0-50]: 1331 680884 Utilized[51-101]: 9 3983 Utilized[102-152]: 3 1187 Utilized[153-203]: 0 0 Utilized[204-255]: 2 539 Utilized[256-306]: 5 1135 Utilized[307-357]: 1 192 Utilized[358-408]: 0 0 Utilized[409-459]: 1 57 Utilized[460-512]: 400 13 Last Scan Time: 223.98 Last Scan Duration: 70.65 Above is a sample obtained from one of our test machines when THP is alwa= ys enabled. Of the 1331 THPs in this thp_utilization sample that have from 0-50 utilized subpages, we see that there are 680884 free pages. This comes out to 680884 / (512 * 1331) =3D 99.91% zero pages in the least utilized bucket. This represents 680884 * 4KB =3D 2.7GB memory waste. Also note that the vast majority of pages are either in the least utilize= d [0-50] or most utilized [460-512] buckets. The least utilized THPs are=20 responsible for almost all of the memory waste when THP is always=20 enabled. Thus by clearing out THPs in the lowest utilization bucket we extract most of the improvement in CPU efficiency. We have seen=20 similar results on our production hosts. This patchset introduces the THP shrinker we have developed to identify and split the least utilized THPs. It includes the thp_utilization=20 changes that groups anonymous THPs into buckets, the split_huge_page() changes that identify and zap zero 4KB pages within THPs and the shrinker changes. It should be noted that the split_huge_page() changes are based off previous work done by Yu Zhao.=20 In the future, we intend to allow additional tuning to the shrinker based on workload depending on CPU/IO/Memory pressure and the=20 amount of anonymous memory. The long term goal is to eventually always=20 enable THP for all applications and deprecate madvise entirely. Alexander Zhu (3): mm: add thp_utilization metrics to debugfs mm: changes to split_huge_page() to free zero filled tail pages mm: THP low utilization shrinker Documentation/admin-guide/mm/transhuge.rst | 9 + include/linux/huge_mm.h | 9 + include/linux/list_lru.h | 24 ++ include/linux/mm_types.h | 5 + include/linux/rmap.h | 2 +- include/linux/vm_event_item.h | 2 + mm/huge_memory.c | 333 +++++++++++++++++- mm/list_lru.c | 49 +++ mm/migrate.c | 60 +++- mm/migrate_device.c | 4 +- mm/page_alloc.c | 6 + mm/vmstat.c | 2 + .../selftests/vm/split_huge_page_test.c | 58 ++- tools/testing/selftests/vm/vm_util.c | 23 ++ tools/testing/selftests/vm/vm_util.h | 1 + 15 files changed, 569 insertions(+), 18 deletions(-) --=20 2.30.2