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 D2AB5E7D0A1 for ; Fri, 22 Sep 2023 00:42:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229532AbjIVAmT (ORCPT ); Thu, 21 Sep 2023 20:42:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229503AbjIVAmS (ORCPT ); Thu, 21 Sep 2023 20:42:18 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4DB08F5 for ; Thu, 21 Sep 2023 17:42:12 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB0CBC433C8; Fri, 22 Sep 2023 00:42:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1695343332; bh=dUG1cnAC65KqfMiKeXdKWYFMm+GzUuR1sodSUWCqEx4=; h=Date:To:From:Subject:From; b=YTl6gIR5FRgRb6aYXLTE9XQZMOAJeMPkiHKIkOpqEwFrp25sRn3Te6dEKycB84sNf CVYi/kMJ2Z1y1VFsHfoQiGk9l/xd9WQ7P4KABJEqYF9CrfkVDqg+NNUFkY+yoDK3/A krNXu9CNYck9ugPx3fQzDTRZxvT9Nbq7llXq7NXo= Date: Thu, 21 Sep 2023 17:42:11 -0700 To: mm-commits@vger.kernel.org, falcon@tinylab.org, wangjiexun@tinylab.org, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-madvise-add-cond_resched-in-madvise_cold_or_pageout_pte_range.patch added to mm-hotfixes-unstable branch Message-Id: <20230922004211.DB0CBC433C8@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/madvise: add cond_resched() in madvise_cold_or_pageout_pte_range() has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-madvise-add-cond_resched-in-madvise_cold_or_pageout_pte_range.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-madvise-add-cond_resched-in-madvise_cold_or_pageout_pte_range.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Jiexun Wang Subject: mm/madvise: add cond_resched() in madvise_cold_or_pageout_pte_range() Date: Thu, 21 Sep 2023 20:27:51 +0800 I conducted real-time testing and observed that madvise_cold_or_pageout_pte_range() causes significant latency under memory pressure, which can be effectively reduced by adding cond_resched() within the loop. I tested on the LicheePi 4A board using Cylictest for latency testing and Ftrace for latency tracing. The board uses TH1520 processor and has a memory size of 8GB. The kernel version is 6.5.0 with the PREEMPT_RT patch applied. The script I tested is as follows: echo wakeup_rt > /sys/kernel/tracing/current_tracer echo 1 > /sys/kernel/tracing/tracing_on echo 0 > /sys/kernel/tracing/tracing_max_latency stress-ng --vm 8 --vm-bytes 2G & cyclictest --mlockall --smp --priority=99 --distance=0 --duration=30m echo 0 > /sys/kernel/tracing/tracing_on cat /sys/kernel/tracing/trace The tracing results before modification are as follows: # tracer: wakeup_rt # # wakeup_rt latency trace v1.1.5 on 6.5.0-rt6-r1208-00003-g999d221864bf # -------------------------------------------------------------------- # latency: 2552 us, #6/6, CPU#3 | (M:preempt_rt VP:0, KP:0, SP:0 HP:0 #P:4) # ----------------- # | task: cyclictest-196 (uid:0 nice:0 policy:1 rt_prio:99) # ----------------- # # _--------=> CPU# # / _-------=> irqs-off/BH-disabled # | / _------=> need-resched # || / _-----=> need-resched-lazy # ||| / _----=> hardirq/softirq # |||| / _---=> preempt-depth # ||||| / _--=> preempt-lazy-depth # |||||| / _-=> migrate-disable # ||||||| / delay # cmd pid |||||||| time | caller # \ / |||||||| \ | / stress-n-206 3dn.h512 2us : 206:120:R + [003] 196: 0:R cyclictest stress-n-206 3dn.h512 7us : => __ftrace_trace_stack => __trace_stack => probe_wakeup => ttwu_do_activate => try_to_wake_up => wake_up_process => hrtimer_wakeup => __hrtimer_run_queues => hrtimer_interrupt => riscv_timer_interrupt => handle_percpu_devid_irq => generic_handle_domain_irq => riscv_intc_irq => handle_riscv_irq => do_irq stress-n-206 3dn.h512 9us#: 0 stress-n-206 3d...3.. 2544us : __schedule stress-n-206 3d...3.. 2545us : 206:120:R ==> [003] 196: 0:R cyclictest stress-n-206 3d...3.. 2551us : => __ftrace_trace_stack => __trace_stack => probe_wakeup_sched_switch => __schedule => preempt_schedule => migrate_enable => rt_spin_unlock => madvise_cold_or_pageout_pte_range => walk_pgd_range => __walk_page_range => walk_page_range => madvise_pageout => madvise_vma_behavior => do_madvise => sys_madvise => do_trap_ecall_u => ret_from_exception The tracing results after modification are as follows: # tracer: wakeup_rt # # wakeup_rt latency trace v1.1.5 on 6.5.0-rt6-r1208-00004-gca3876fc69a6-dirty # -------------------------------------------------------------------- # latency: 1689 us, #6/6, CPU#0 | (M:preempt_rt VP:0, KP:0, SP:0 HP:0 #P:4) # ----------------- # | task: cyclictest-217 (uid:0 nice:0 policy:1 rt_prio:99) # ----------------- # # _--------=> CPU# # / _-------=> irqs-off/BH-disabled # | / _------=> need-resched # || / _-----=> need-resched-lazy # ||| / _----=> hardirq/softirq # |||| / _---=> preempt-depth # ||||| / _--=> preempt-lazy-depth # |||||| / _-=> migrate-disable # ||||||| / delay # cmd pid |||||||| time | caller # \ / |||||||| \ | / stress-n-232 0dn.h413 1us+: 232:120:R + [000] 217: 0:R cyclictest stress-n-232 0dn.h413 12us : => __ftrace_trace_stack => __trace_stack => probe_wakeup => ttwu_do_activate => try_to_wake_up => wake_up_process => hrtimer_wakeup => __hrtimer_run_queues => hrtimer_interrupt => riscv_timer_interrupt => handle_percpu_devid_irq => generic_handle_domain_irq => riscv_intc_irq => handle_riscv_irq => do_irq stress-n-232 0dn.h413 19us#: 0 stress-n-232 0d...3.. 1671us : __schedule stress-n-232 0d...3.. 1676us+: 232:120:R ==> [000] 217: 0:R cyclictest stress-n-232 0d...3.. 1687us : => __ftrace_trace_stack => __trace_stack => probe_wakeup_sched_switch => __schedule => preempt_schedule => migrate_enable => free_unref_page_list => release_pages => free_pages_and_swap_cache => tlb_batch_pages_flush => tlb_flush_mmu => unmap_page_range => unmap_vmas => unmap_region => do_vmi_align_munmap.constprop.0 => do_vmi_munmap => __vm_munmap => sys_munmap => do_trap_ecall_u => ret_from_exception After the modification, the cause of maximum latency is no longer madvise_cold_or_pageout_pte_range(), so this modification can reduce the latency caused by madvise_cold_or_pageout_pte_range(). Currently the madvise_cold_or_pageout_pte_range() function exhibits significant latency under memory pressure, which can be effectively reduced by adding cond_resched() within the loop. When the batch_count reaches SWAP_CLUSTER_MAX, we reschedule the task to ensure fairness and avoid long lock holding times. Link: https://lkml.kernel.org/r/85363861af65fac66c7a98c251906afc0d9c8098.1695291046.git.wangjiexun@tinylab.org Signed-off-by: Jiexun Wang Cc: Zhangjin Wu Signed-off-by: Andrew Morton --- mm/madvise.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/mm/madvise.c~mm-madvise-add-cond_resched-in-madvise_cold_or_pageout_pte_range +++ a/mm/madvise.c @@ -353,6 +353,7 @@ static int madvise_cold_or_pageout_pte_r struct folio *folio = NULL; LIST_HEAD(folio_list); bool pageout_anon_only_filter; + unsigned int batch_count = 0; if (fatal_signal_pending(current)) return -EINTR; @@ -434,6 +435,7 @@ huge_unlock: regular_folio: #endif tlb_change_page_size(tlb, PAGE_SIZE); +restart: start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); if (!start_pte) return 0; @@ -442,6 +444,15 @@ regular_folio: for (; addr < end; pte++, addr += PAGE_SIZE) { ptent = ptep_get(pte); + if (++batch_count == SWAP_CLUSTER_MAX) { + batch_count = 0; + if (need_resched()) { + pte_unmap_unlock(start_pte, ptl); + cond_resched(); + goto restart; + } + } + if (pte_none(ptent)) continue; _ Patches currently in -mm which might be from wangjiexun@tinylab.org are mm-madvise-add-cond_resched-in-madvise_cold_or_pageout_pte_range.patch