From nobody Wed Dec 17 08:11:59 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 6166AC47072 for ; Wed, 15 Nov 2023 09:05:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234724AbjKOJFV (ORCPT ); Wed, 15 Nov 2023 04:05:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41870 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234718AbjKOJFB (ORCPT ); Wed, 15 Nov 2023 04:05:01 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B30B11F; Wed, 15 Nov 2023 01:04:57 -0800 (PST) Date: Wed, 15 Nov 2023 09:04:55 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1700039096; h=from:from:sender:sender:reply-to: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=sRzwwgL0YArqRaYB+PBQmPDmbmjCfGOodH5XxvM07D8=; b=vre0JfoEr5u6zxvAC6yptC1xRoqvF6YaerGv+lCrROiSyAzlGsCSm0HGnUOoddSKf/vsV4 DBIYZmp4HE4uFFjBvKA521aYOSgtloF3Z4Kme6vTkZMO0w8XleqVFP4jV2VFVmMS06mo9E dXHysemxklTuUGSFxTeCq6Ql/IVtzoSTq4X/Vhas80KCyHw82vTpVF/ULUIlkuyDHmt0YZ 0+sltwtdzhq/XGgV01L5FeDCxxL/6dgvKKRfwfXdhdFxM2/IrJuOFGGqeHFGcJKmlh63Pc Wkp+q1z9UZYHQMusE9e4vtfOdl2QCUd9eaZi5xtPrp2zudnZVc6QGhytPVkneg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1700039096; h=from:from:sender:sender:reply-to: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=sRzwwgL0YArqRaYB+PBQmPDmbmjCfGOodH5XxvM07D8=; b=s4AfFs/LKowDPOfjKdtn1shlbfVNlc3E0RUu2CYllC4x2ZH+M0mxHC2BfhM++iRp8DiLx+ 5bHcYvJTlaFuKKDA== From: "tip-bot2 for Raghavendra K T" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/numa: Fix mm numa_scan_seq based unconditional scan Cc: Raghavendra K T , "Peter Zijlstra (Intel)" , Mel Gorman , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: =?utf-8?q?=3C2ea7cbce80ac7c62e90cbfb9653a7972f902439f=2E16978?= =?utf-8?q?16692=2Egit=2Eraghavendra=2Ekt=40amd=2Ecom=3E?= References: =?utf-8?q?=3C2ea7cbce80ac7c62e90cbfb9653a7972f902439f=2E169781?= =?utf-8?q?6692=2Egit=2Eraghavendra=2Ekt=40amd=2Ecom=3E?= MIME-Version: 1.0 Message-ID: <170003909541.391.12348642346090919555.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 84db47ca7146d7bd00eb5cf2b93989a971c84650 Gitweb: https://git.kernel.org/tip/84db47ca7146d7bd00eb5cf2b93989a97= 1c84650 Author: Raghavendra K T AuthorDate: Fri, 20 Oct 2023 21:27:46 +05:30 Committer: Peter Zijlstra CommitterDate: Wed, 15 Nov 2023 09:57:46 +01:00 sched/numa: Fix mm numa_scan_seq based unconditional scan Since commit fc137c0ddab2 ("sched/numa: enhance vma scanning logic") NUMA Balancing allows updating PTEs to trap NUMA hinting faults if the task had previously accessed VMA. However unconditional scan of VMAs are allowed during initial phase of VMA creation until process's mm numa_scan_seq reaches 2 even though current task had not accessed VMA. Rationale: - Without initial scan subsequent PTE update may never happen. - Give fair opportunity to all the VMAs to be scanned and subsequently understand the access pattern of all the VMAs. But it has a corner case where, if a VMA is created after some time, process's mm numa_scan_seq could be already greater than 2. For e.g., values of mm numa_scan_seq when VMAs are created by running mmtest autonuma benchmark briefly looks like: start_seq=3D0 : 459 start_seq=3D2 : 138 start_seq=3D3 : 144 start_seq=3D4 : 8 start_seq=3D8 : 1 start_seq=3D9 : 1 This results in no unconditional PTE updates for those VMAs created after some time. Fix: - Note down the initial value of mm numa_scan_seq in per VMA start_seq. - Allow unconditional scan till start_seq + 2. Result: SUT: AMD EPYC Milan with 2 NUMA nodes 256 cpus. base kernel: upstream 6.6-rc6 with Mels patches [1] applied. kernbench =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D base patched %gain Amean elsp-128 165.09 ( 0.00%) 164.78 * 0.19%* Duration User 41404.28 41375.08 Duration System 9862.22 9768.48 Duration Elapsed 519.87 518.72 Ops NUMA PTE updates 1041416.00 831536.00 Ops NUMA hint faults 263296.00 220966.00 Ops NUMA pages migrated 258021.00 212769.00 Ops AutoNUMA cost 1328.67 1114.69 autonumabench NUMA01_THREADLOCAL =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Amean elsp-NUMA01_THREADLOCAL 81.79 (0.00%) 67.74 * 17.18%* Duration User 54832.73 47379.67 Duration System 75.00 185.75 Duration Elapsed 576.72 476.09 Ops NUMA PTE updates 394429.00 11121044.00 Ops NUMA hint faults 1001.00 8906404.00 Ops NUMA pages migrated 288.00 2998694.00 Ops AutoNUMA cost 7.77 44666.84 Signed-off-by: Raghavendra K T Signed-off-by: Peter Zijlstra (Intel) Acked-by: Mel Gorman Link: https://lore.kernel.org/r/2ea7cbce80ac7c62e90cbfb9653a7972f902439f.16= 97816692.git.raghavendra.kt@amd.com --- include/linux/mm_types.h | 3 +++ kernel/sched/fair.c | 4 +++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 957ce38..950df41 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -600,6 +600,9 @@ struct vma_numab_state { */ unsigned long pids_active[2]; =20 + /* MM scan sequence ID when scan first started after VMA creation */ + int start_scan_seq; + /* * MM scan sequence ID when the VMA was last completely scanned. * A VMA is not eligible for scanning if prev_scan_seq =3D=3D numa_scan_s= eq diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d7a3c63..44b5262 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3164,7 +3164,7 @@ static bool vma_is_accessed(struct mm_struct *mm, str= uct vm_area_struct *vma) * This is also done to avoid any side effect of task scanning * amplifying the unfairness of disjoint set of VMAs' access. */ - if (READ_ONCE(current->mm->numa_scan_seq) < 2) + if ((READ_ONCE(current->mm->numa_scan_seq) - vma->numab_state->start_scan= _seq) < 2) return true; =20 pids =3D vma->numab_state->pids_active[0] | vma->numab_state->pids_active= [1]; @@ -3307,6 +3307,8 @@ retry_pids: if (!vma->numab_state) continue; =20 + vma->numab_state->start_scan_seq =3D mm->numa_scan_seq; + vma->numab_state->next_scan =3D now + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);