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 F12C7C004D4 for ; Thu, 19 Jan 2023 09:40:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229910AbjASJkO (ORCPT ); Thu, 19 Jan 2023 04:40:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230177AbjASJj6 (ORCPT ); Thu, 19 Jan 2023 04:39:58 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 368166B9A5 for ; Thu, 19 Jan 2023 01:39:54 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8F6A761384 for ; Thu, 19 Jan 2023 09:39:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0AE5C433EF; Thu, 19 Jan 2023 09:39:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1674121193; bh=oC4rK1vElis6p5UZEhMNSBbWkHGAXkm0JBiBL1EnbyM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZYHsHP0Mmss5O6jrrdgh9VRP8MrCsP4GP6MitJFyW3HxUxoxwifctz8cD/uLuqokI 4ZfSATGVdLbN6QJ4z4tGVHPFqavkPJvqZi6a8M1EuoX4qUs43djPluB+n0UXv8MDNa 4ZDxkNTYWKED8vb1JLuDXOuLz87reKSzKPBrQe1iXDKDtRIyiN8ogm4nGMy06cr9/Y teXR1sKxx2QhLAuGwmyMo89vNXBeNpcKUXVbn2Wwo6ueZuATmNEajDnt0pInCC3oR3 yWlZCKewxkMonojOO5ht0RGTWqLW7joTDrNLW39TOi8zzERCrydbEaSLlO6A/ZvmMr s9dUJtvVqJfcg== Date: Thu, 19 Jan 2023 11:39:36 +0200 From: Mike Rapoport To: Raghavendra K T Cc: = , linux-mm@kvack.org, --cc=Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Andrew Morton , Matthew Wilcox , Vlastimil Babka , "Liam R . Howlett" , Peter Xu , David Hildenbrand , xu xin , Yu Zhao , Colin Cross , Arnd Bergmann , Hugh Dickins , Bharata B Rao , Disha Talreja Subject: Re: [RFC PATCH V1 1/1] sched/numa: Enhance vma scanning logic Message-ID: References: <67bf778d592c39d02444825c416c2ed11d2ef4b2.1673610485.git.raghavendra.kt@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <67bf778d592c39d02444825c416c2ed11d2ef4b2.1673610485.git.raghavendra.kt@amd.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Mon, Jan 16, 2023 at 07:05:34AM +0530, Raghavendra K T wrote: > During the Numa scanning make sure only relevant vmas of the > tasks are scanned. Please add more detailed description about what are the issues with the current scanning this patch aims to solve. > Logic: > 1) For the first two time allow unconditional scanning of vmas > 2) Store recent 4 unique tasks (last 8bits of PIDs) accessed the vma. > False negetives in case of collison should be fine here. ^ negatives > 3) If more than 4 pids exist assume task indeed accessed vma to > to avoid false negetives > > Co-developed-by: Bharata B Rao > (initial patch to store pid information) > > Suggested-by: Mel Gorman > Signed-off-by: Bharata B Rao > Signed-off-by: Raghavendra K T > --- > include/linux/mm_types.h | 2 ++ > kernel/sched/fair.c | 32 ++++++++++++++++++++++++++++++++ > mm/memory.c | 21 +++++++++++++++++++++ > 3 files changed, 55 insertions(+) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 500e536796ca..07feae37b8e6 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -506,6 +506,8 @@ struct vm_area_struct { > struct mempolicy *vm_policy; /* NUMA policy for the VMA */ > #endif > struct vm_userfaultfd_ctx vm_userfaultfd_ctx; > + unsigned int accessing_pids; > + int next_pid_slot; > } __randomize_layout; > > struct kioctx_table; > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index e4a0b8bd941c..944d2e3b0b3c 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2916,6 +2916,35 @@ static void reset_ptenuma_scan(struct task_struct *p) > p->mm->numa_scan_offset = 0; > } > > +static bool vma_is_accessed(struct vm_area_struct *vma) > +{ > + int i; > + bool more_pids_exist; > + unsigned long pid, max_pids; > + unsigned long current_pid = current->pid & LAST__PID_MASK; > + > + max_pids = sizeof(unsigned int) * BITS_PER_BYTE / LAST__PID_SHIFT; > + > + /* By default we assume >= max_pids exist */ > + more_pids_exist = true; > + > + if (READ_ONCE(current->mm->numa_scan_seq) < 2) > + return true; > + > + for (i = 0; i < max_pids; i++) { > + pid = (vma->accessing_pids >> i * LAST__PID_SHIFT) & > + LAST__PID_MASK; > + if (pid == current_pid) > + return true; > + if (pid == 0) { > + more_pids_exist = false; > + break; > + } > + } > + > + return more_pids_exist; > +} > + > /* > * The expensive part of numa migration is done from task_work context. > * Triggered from task_tick_numa(). > @@ -3015,6 +3044,9 @@ static void task_numa_work(struct callback_head *work) > if (!vma_is_accessible(vma)) > continue; > > + if (!vma_is_accessed(vma)) > + continue; > + > do { > start = max(start, vma->vm_start); > end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE); > diff --git a/mm/memory.c b/mm/memory.c > index 8c8420934d60..fafd78d87a51 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4717,7 +4717,28 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) > pte_t pte, old_pte; > bool was_writable = pte_savedwrite(vmf->orig_pte); > int flags = 0; > + int pid_slot = vma->next_pid_slot; > > + int i; > + unsigned long pid, max_pids; > + unsigned long current_pid = current->pid & LAST__PID_MASK; > + > + max_pids = sizeof(unsigned int) * BITS_PER_BYTE / LAST__PID_SHIFT; > + > + /* Avoid duplicate PID updation */ > + for (i = 0; i < max_pids; i++) { > + pid = (vma->accessing_pids >> i * LAST__PID_SHIFT) & > + LAST__PID_MASK; > + if (pid == current_pid) > + goto skip_update; > + } > + > + vma->next_pid_slot = (++pid_slot) % max_pids; > + vma->accessing_pids &= ~(LAST__PID_MASK << (pid_slot * LAST__PID_SHIFT)); > + vma->accessing_pids |= ((current_pid) << > + (pid_slot * LAST__PID_SHIFT)); > + > +skip_update: > /* > * The "pte" at this point cannot be used safely without > * validation through pte_unmap_same(). It's of NUMA type but > -- > 2.34.1 > > -- Sincerely yours, Mike.