From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-f71.google.com (mail-lf1-f71.google.com [209.85.167.71]) by kanga.kvack.org (Postfix) with ESMTP id 9DA526B04C2 for ; Wed, 7 Nov 2018 02:02:59 -0500 (EST) Received: by mail-lf1-f71.google.com with SMTP id w13-v6so1960253lfe.6 for ; Tue, 06 Nov 2018 23:02:59 -0800 (PST) Received: from forwardcorp1j.cmail.yandex.net (forwardcorp1j.cmail.yandex.net. [5.255.227.105]) by mx.google.com with ESMTPS id d202si25855865lfe.126.2018.11.06.23.02.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Nov 2018 23:02:57 -0800 (PST) Subject: Re: [PATCH v1 0/4]mm: convert totalram_pages, totalhigh_pages and managed pages to atomic References: <1540551662-26458-1-git-send-email-arunks@codeaurora.org> <9b210d4cc9925caf291412d7d45f16d7@codeaurora.org> <63d9f48c-e39f-d345-0fb6-2f04afe769a2@yandex-team.ru> <08a61c003eed0280fd82f6200debcbca@codeaurora.org> <10c88df6-dbb1-7490-628c-055d59b5ad8e@yandex-team.ru> <22fa2222012341a54f6b0b6aea341aa2@codeaurora.org> From: Konstantin Khlebnikov Message-ID: Date: Wed, 7 Nov 2018 10:02:55 +0300 MIME-Version: 1.0 In-Reply-To: <22fa2222012341a54f6b0b6aea341aa2@codeaurora.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-CA Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Arun KS Cc: keescook@chromium.org, minchan@kernel.org, getarunks@gmail.com, gregkh@linuxfoundation.org, akpm@linux-foundation.org, mhocko@kernel.org, vbabka@suse.cz, linux-kernel@vger.kernel.org, linux-mm@kvack.org, julia.lawall@lip6.fr On 06.11.2018 11:43, Arun KS wrote: > On 2018-11-06 14:07, Konstantin Khlebnikov wrote: >> On 06.11.2018 11:30, Arun KS wrote: >>> On 2018-11-06 13:47, Konstantin Khlebnikov wrote: >>>> On 06.11.2018 8:38, Arun KS wrote: >>>>> Any comments? >>>> >>>> Looks good. >>>> Except unclear motivation behind this change. >>>> This should be in comment of one of patch. >>> >>> totalram_pages, zone->managed_pages and totalhigh_pages are sometimes modified outside managed_page_count_lock. Hence convert these >>> variable to atomic to avoid readers potentially seeing a store tear. >> >> So, this is just theoretical issue or splat from sanitizer. >> After boot memory online\offline are strictly serialized by rw-semaphore. > > Few instances which can race with hot add. Please see below, > https://patchwork.kernel.org/patch/10627521/ Could you point what exactly are you fixing with this set? from v2: > totalram_pages, zone->managed_pages and totalhigh_pages updates > are protected by managed_page_count_lock, but readers never care > about it. Convert these variables to atomic to avoid readers > potentially seeing a store tear. This? Aligned unsigned long almost always stored at once. To make it completely correct you could replace a += b; with WRITE_ONCE(a, a + b); > > Regards, > Arun > >> >>> >>> Will update the comment. >>> >>> Regards, >>> Arun >>> >>>> >>>> Reviewed-by: Konstantin Khlebnikov >>>> >>>>> >>>>> Regards, >>>>> Arun >>>>> >>>>> On 2018-10-26 16:30, Arun KS wrote: >>>>>> This series convert totalram_pages, totalhigh_pages and >>>>>> zone->managed_pages to atomic variables. >>>>>> >>>>>> The patch was comiple tested on x86(x86_64_defconfig & i386_defconfig) >>>>>> on tip of linux-mmotm. And memory hotplug tested on arm64, but on an >>>>>> older version of kernel. >>>>>> >>>>>> Arun KS (4): >>>>>> A mm: Fix multiple evaluvations of totalram_pages and managed_pages >>>>>> A mm: Convert zone->managed_pages to atomic variable >>>>>> A mm: convert totalram_pages and totalhigh_pages variables to atomic >>>>>> A mm: Remove managed_page_count spinlock >>>>>> >>>>>> A arch/csky/mm/init.cA A A A A A A A A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A arch/powerpc/platforms/pseries/cmm.cA A A A A A A A A | 10 ++-- >>>>>> A arch/s390/mm/init.cA A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A arch/um/kernel/mem.cA A A A A A A A A A A A A A A A A A A A A A A A A |A 3 +- >>>>>> A arch/x86/kernel/cpu/microcode/core.cA A A A A A A A A |A 5 +- >>>>>> A drivers/char/agp/backend.cA A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A drivers/gpu/drm/amd/amdkfd/kfd_crat.cA A A A A A A A |A 2 +- >>>>>> A drivers/gpu/drm/i915/i915_gem.cA A A A A A A A A A A A A A |A 2 +- >>>>>> A drivers/gpu/drm/i915/selftests/i915_gem_gtt.c |A 4 +- >>>>>> A drivers/hv/hv_balloon.cA A A A A A A A A A A A A A A A A A A A A A | 19 +++---- >>>>>> A drivers/md/dm-bufio.cA A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A drivers/md/dm-crypt.cA A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A drivers/md/dm-integrity.cA A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A drivers/md/dm-stats.cA A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A drivers/media/platform/mtk-vpu/mtk_vpu.cA A A A A |A 2 +- >>>>>> A drivers/misc/vmw_balloon.cA A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A drivers/parisc/ccio-dma.cA A A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A drivers/parisc/sba_iommu.cA A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A drivers/staging/android/ion/ion_system_heap.c |A 2 +- >>>>>> A drivers/xen/xen-selfballoon.cA A A A A A A A A A A A A A A A |A 6 +-- >>>>>> A fs/ceph/super.hA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A fs/file_table.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 7 +-- >>>>>> A fs/fuse/inode.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A fs/nfs/write.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A fs/nfsd/nfscache.cA A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A fs/ntfs/malloc.hA A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A fs/proc/base.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A include/linux/highmem.hA A A A A A A A A A A A A A A A A A A A A A | 28 ++++++++++- >>>>>> A include/linux/mm.hA A A A A A A A A A A A A A A A A A A A A A A A A A A | 27 +++++++++- >>>>>> A include/linux/mmzone.hA A A A A A A A A A A A A A A A A A A A A A A | 15 +++--- >>>>>> A include/linux/swap.hA A A A A A A A A A A A A A A A A A A A A A A A A |A 1 - >>>>>> A kernel/fork.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 5 +- >>>>>> A kernel/kexec_core.cA A A A A A A A A A A A A A A A A A A A A A A A A A |A 5 +- >>>>>> A kernel/power/snapshot.cA A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A lib/show_mem.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/highmem.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A mm/huge_memory.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/kasan/quarantine.cA A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/memblock.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 6 +-- >>>>>> A mm/memory_hotplug.cA A A A A A A A A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A mm/mm_init.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/oom_kill.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/page_alloc.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A | 71 +++++++++++++-------------- >>>>>> A mm/shmem.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 7 +-- >>>>>> A mm/slab.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/swap.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/util.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/vmalloc.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A mm/vmstat.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A mm/workingset.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A mm/zswap.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 4 +- >>>>>> A net/dccp/proto.cA A A A A A A A A A A A A A A A A A A A A A A A A A A A A |A 7 +-- >>>>>> A net/decnet/dn_route.cA A A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A net/ipv4/tcp_metrics.cA A A A A A A A A A A A A A A A A A A A A A A |A 2 +- >>>>>> A net/netfilter/nf_conntrack_core.cA A A A A A A A A A A A |A 7 +-- >>>>>> A net/netfilter/xt_hashlimit.cA A A A A A A A A A A A A A A A A |A 5 +- >>>>>> A net/sctp/protocol.cA A A A A A A A A A A A A A A A A A A A A A A A A A |A 7 +-- >>>>>> A security/integrity/ima/ima_kexec.cA A A A A A A A A A A |A 2 +- >>>>>> A 58 files changed, 195 insertions(+), 144 deletions(-)