From nobody Wed Dec 17 19:20:52 2025 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 778FAC0015E for ; Thu, 17 Aug 2023 03:53:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347926AbjHQDxF (ORCPT ); Wed, 16 Aug 2023 23:53:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53188 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347923AbjHQDwt (ORCPT ); Wed, 16 Aug 2023 23:52:49 -0400 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EF6526AB; Wed, 16 Aug 2023 20:52:47 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045176;MF=liusong@linux.alibaba.com;NM=1;PH=DS;RN=11;SR=0;TI=SMTPD_---0VpyHzpK_1692244315; Received: from localhost(mailfrom:liusong@linux.alibaba.com fp:SMTPD_---0VpyHzpK_1692244315) by smtp.aliyun-inc.com; Thu, 17 Aug 2023 11:52:44 +0800 From: Liu Song To: corbet@lwn.net, akpm@linux-foundation.org, paulmck@kernel.org, rdunlap@infradead.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, rostedt@goodmis.org Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liusong@linux.alibaba.com Subject: [PATCH] mm/khugepaged: increase transparent_hugepage_recommend_disable parameter to disable active modification of min_free_kbytes Date: Thu, 17 Aug 2023 11:51:55 +0800 Message-Id: <20230817035155.84230-1-liusong@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" In the arm64 environment, when PAGESIZE is 4K, the "pageblock_nr_pages" value is 512, and the recommended min_free_kbytes in "set_recommended_min_free_kbytes" usually does not exceed 44MB. However, when PAGESIZE is 64K, the "pageblock_nr_pages" value is 8192, and the recommended min_free_kbytes in "set_recommended_min_free_kbytes" is 8192 * 2 * (2 + 9) * 64K, which directly increases to 11GB. According to this calculation method, due to the modification of min_free_k= bytes, the reserved memory in my 128GB memory environment reaches 10GB, and MemAva= ilable is correspondingly reduced by 10GB. In the case of PAGESIZE 64K, transparent hugepages are 512MB, and we only need them to be used on demand. If transparent hugepages cannot be allocate= d, falling back to regular 64K pages is completely acceptable. Therefore, we added the transparent_hugepage_recommend_disable parameter to disable active modification of min_free_kbytes, thereby meeting our requirements for transparent hugepages in the 64K scenario, and it will not excessively reduce the available memory. Signed-off-by: Liu Song --- .../admin-guide/kernel-parameters.txt | 5 +++++ mm/khugepaged.c | 20 ++++++++++++++++++- 2 files changed, 24 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 654d0d921101..612bdf601cce 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6553,6 +6553,11 @@ See Documentation/admin-guide/mm/transhuge.rst for more details. =20 + transparent_hugepage_recommend_disable + [KNL,THP] + Can be used to disable transparent hugepage to actively modify + /proc/sys/vm/min_free_kbytes during enablement process. + trusted.source=3D [KEYS] Format: This parameter identifies the trust source as a backend diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 78fc1a24a1cc..ac40c618f4f6 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -88,6 +88,9 @@ static unsigned int khugepaged_max_ptes_none __read_mostl= y; static unsigned int khugepaged_max_ptes_swap __read_mostly; static unsigned int khugepaged_max_ptes_shared __read_mostly; =20 +/* default enable recommended */ +static unsigned int transparent_hugepage_recommend __read_mostly =3D 1; + #define MM_SLOTS_HASH_BITS 10 static DEFINE_READ_MOSTLY_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); =20 @@ -2561,6 +2564,11 @@ static void set_recommended_min_free_kbytes(void) goto update_wmarks; } =20 + if (!transparent_hugepage_recommend) { + pr_info("do not allow to recommend modify min_free_kbytes\n"); + return; + } + for_each_populated_zone(zone) { /* * We don't need to worry about fragmentation of @@ -2591,7 +2599,10 @@ static void set_recommended_min_free_kbytes(void) =20 if (recommended_min > min_free_kbytes) { if (user_min_free_kbytes >=3D 0) - pr_info("raising min_free_kbytes from %d to %lu to help transparent hug= epage allocations\n", + pr_info("raising user specified min_free_kbytes from %d to %lu to help = transparent hugepage allocations\n", + min_free_kbytes, recommended_min); + else + pr_info("raising default min_free_kbytes from %d to %lu to help transpa= rent hugepage allocations\n", min_free_kbytes, recommended_min); =20 min_free_kbytes =3D recommended_min; @@ -2601,6 +2612,13 @@ static void set_recommended_min_free_kbytes(void) setup_per_zone_wmarks(); } =20 +static int __init setup_transparent_hugepage_recommend_disable(char *str) +{ + transparent_hugepage_recommend =3D 0; + return 1; +} +__setup("transparent_hugepage_recommend_disable", setup_transparent_hugepa= ge_recommend_disable); + int start_stop_khugepaged(void) { int err =3D 0; --=20 2.19.1.6.gb485710b