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 29DB7C6FD19 for ; Mon, 13 Mar 2023 18:07:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229734AbjCMSH2 (ORCPT ); Mon, 13 Mar 2023 14:07:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229909AbjCMSH1 (ORCPT ); Mon, 13 Mar 2023 14:07:27 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 270C94C6EF for ; Mon, 13 Mar 2023 11:07:26 -0700 (PDT) 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 B64BE61454 for ; Mon, 13 Mar 2023 18:07:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10BCFC433D2; Mon, 13 Mar 2023 18:07:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1678730845; bh=TLLpJFa4SmJPwcoPlRkksxhxMmYcaJoD83veLXk+j74=; h=Date:To:From:Subject:From; b=A44NHSTJo62Mx6EH9+JEm15ScQLnyfpLtEJVYYPEBhmrlpH0afQoMVKx56nv2yBJq rHHrZYk/CdM+gi//l/09pSz4BVKn6BUphBK+G8+BmXDS7FLeRzKdFfs6AGs8k9M0aC 3mMlDWDW+h56IJfoKJmoHxjWaz7HUoR6b+uXJ+Ao= Date: Mon, 13 Mar 2023 11:07:24 -0700 To: mm-commits@vger.kernel.org, willy@infradead.org, vbabka@suse.cz, thomas.hellstrom@linux.intel.com, peterx@redhat.com, mhocko@suse.com, lstoakes@gmail.com, linux@armlinux.org.uk, kirill.shutemov@linux.intel.com, jgg@ziepe.ca, hca@linux.ibm.com, frederic@kernel.org, dan.j.williams@intel.com, cl@linux.com, christian.koenig@amd.com, chenhuacai@kernel.org, atomlin@atomlin.com, mtosatti@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + this_cpu_cmpxchg-arm64-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch added to mm-unstable branch Message-Id: <20230313180725.10BCFC433D2@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: this_cpu_cmpxchg: ARM64: switch this_cpu_cmpxchg to locked, add _local function has been added to the -mm mm-unstable branch. Its filename is this_cpu_cmpxchg-arm64-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/this_cpu_cmpxchg-arm64-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch This patch will later appear in the mm-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: Marcelo Tosatti Subject: this_cpu_cmpxchg: ARM64: switch this_cpu_cmpxchg to locked, add _local function Date: Mon, 13 Mar 2023 13:25:08 -0300 Patch series "fold per-CPU vmstats remotely", v5. This patch series addresses the following two problems: 1. A customer provided some evidence which indicates that the idle tick was stopped; albeit, CPU-specific vmstat counters still remained populated. Thus one can only assume quiet_vmstat() was not invoked on return to the idle loop. If I understand correctly, I suspect this divergence might erroneously prevent a reclaim attempt by kswapd. If the number of zone specific free pages are below their per-cpu drift value then zone_page_state_snapshot() is used to compute a more accurate view of the aforementioned statistic. Thus any task blocked on the NUMA node specific pfmemalloc_wait queue will be unable to make significant progress via direct reclaim unless it is killed after being woken up by kswapd (see throttle_direct_reclaim()) 2. With a SCHED_FIFO task that busy loops on a given CPU, and kworker for that CPU at SCHED_OTHER priority, queuing work to sync per-vmstats will either cause that work to never execute, or stalld (i.e. stall daemon) boosts kworker priority which causes a latency violation By having vmstat_shepherd flush the per-CPU counters to the global counters from remote CPUs. This is done using cmpxchg to manipulate the counters, both CPU locally (via the account functions), and remotely (via cpu_vm_stats_fold). Thanks to Aaron Tomlin for diagnosing issue 1 and writing the initial patch series. This patch (of 5): Goal is to have vmstat_shepherd to transfer from per-CPU counters to global counters remotely. For this, an atomic this_cpu_cmpxchg is necessary. Following the kernel convention for cmpxchg/cmpxchg_local, change ARM's this_cpu_cmpxchg_ helpers to be atomic, and add this_cpu_cmpxchg_local_ helpers which are not atomic. Link: https://lkml.kernel.org/r/20230313162507.032200398@redhat.com Link: https://lkml.kernel.org/r/20230313162634.283504192@redhat.com Signed-off-by: Marcelo Tosatti Cc: Aaron Tomlin Cc: Christoph Lameter Cc: Frederic Weisbecker Cc: Heiko Carstens Cc: Huacai Chen Cc: "Russell King (Oracle)" Cc: Vlastimil Babka Cc: Christian König Cc: Dan Williams Cc: Jason Gunthorpe Cc: Kirill A. Shutemov Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Peter Xu Cc: Thomas Hellström Signed-off-by: Andrew Morton --- --- a/arch/arm64/include/asm/percpu.h~this_cpu_cmpxchg-arm64-switch-this_cpu_cmpxchg-to-locked-add-_local-function +++ a/arch/arm64/include/asm/percpu.h @@ -232,13 +232,23 @@ PERCPU_RET_OP(add, add, ldadd) _pcp_protect_return(xchg_relaxed, pcp, val) #define this_cpu_cmpxchg_1(pcp, o, n) \ - _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) + _pcp_protect_return(cmpxchg, pcp, o, n) #define this_cpu_cmpxchg_2(pcp, o, n) \ - _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) + _pcp_protect_return(cmpxchg, pcp, o, n) #define this_cpu_cmpxchg_4(pcp, o, n) \ - _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) + _pcp_protect_return(cmpxchg, pcp, o, n) #define this_cpu_cmpxchg_8(pcp, o, n) \ + _pcp_protect_return(cmpxchg, pcp, o, n) + +#define this_cpu_cmpxchg_local_1(pcp, o, n) \ _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) +#define this_cpu_cmpxchg_local_2(pcp, o, n) \ + _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) +#define this_cpu_cmpxchg_local_4(pcp, o, n) \ + _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) +#define this_cpu_cmpxchg_local_8(pcp, o, n) \ + _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) + #ifdef __KVM_NVHE_HYPERVISOR__ extern unsigned long __hyp_per_cpu_offset(unsigned int cpu); _ Patches currently in -mm which might be from mtosatti@redhat.com are this_cpu_cmpxchg-arm64-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch this_cpu_cmpxchg-loongarch-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch this_cpu_cmpxchg-s390-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch this_cpu_cmpxchg-x86-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch add-this_cpu_cmpxchg_local-and-asm-generic-definitions.patch convert-this_cpu_cmpxchg-users-to-this_cpu_cmpxchg_local.patch mm-vmstat-switch-counter-modification-to-cmpxchg.patch vmstat-switch-per-cpu-vmstat-counters-to-32-bits.patch mm-vmstat-use-xchg-in-cpu_vm_stats_fold.patch mm-vmstat-switch-vmstat-shepherd-to-flush-per-cpu-counters-remotely.patch mm-vmstat-refresh-stats-remotely-instead-of-via-work-item.patch vmstat-add-pcp-remote-node-draining-via-cpu_vm_stats_fold.patch