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Message-ID: <c3b0edf9-e6a2-c1ab-8490-d94b9830c8ae@yandex-team.ru>
Date: Wed, 7 Nov 2018 10:02:55 +0300
From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To: Arun KS <arunks@...eaurora.org>
Cc: keescook@...omium.org, minchan@...nel.org, getarunks@...il.com,
gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
mhocko@...nel.org, vbabka@...e.cz, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, julia.lawall@...6.fr
Subject: Re: [PATCH v1 0/4]mm: convert totalram_pages, totalhigh_pages and
managed pages to atomic
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 <khlebnikov@...dex-team.ru>
>>>>
>>>>>
>>>>> 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):
>>>>>> mm: Fix multiple evaluvations of totalram_pages and managed_pages
>>>>>> mm: Convert zone->managed_pages to atomic variable
>>>>>> mm: convert totalram_pages and totalhigh_pages variables to atomic
>>>>>> mm: Remove managed_page_count spinlock
>>>>>>
>>>>>> arch/csky/mm/init.c | 4 +-
>>>>>> arch/powerpc/platforms/pseries/cmm.c | 10 ++--
>>>>>> arch/s390/mm/init.c | 2 +-
>>>>>> arch/um/kernel/mem.c | 3 +-
>>>>>> arch/x86/kernel/cpu/microcode/core.c | 5 +-
>>>>>> drivers/char/agp/backend.c | 4 +-
>>>>>> drivers/gpu/drm/amd/amdkfd/kfd_crat.c | 2 +-
>>>>>> drivers/gpu/drm/i915/i915_gem.c | 2 +-
>>>>>> drivers/gpu/drm/i915/selftests/i915_gem_gtt.c | 4 +-
>>>>>> drivers/hv/hv_balloon.c | 19 +++----
>>>>>> drivers/md/dm-bufio.c | 2 +-
>>>>>> drivers/md/dm-crypt.c | 2 +-
>>>>>> drivers/md/dm-integrity.c | 2 +-
>>>>>> drivers/md/dm-stats.c | 2 +-
>>>>>> drivers/media/platform/mtk-vpu/mtk_vpu.c | 2 +-
>>>>>> drivers/misc/vmw_balloon.c | 2 +-
>>>>>> drivers/parisc/ccio-dma.c | 4 +-
>>>>>> drivers/parisc/sba_iommu.c | 4 +-
>>>>>> drivers/staging/android/ion/ion_system_heap.c | 2 +-
>>>>>> drivers/xen/xen-selfballoon.c | 6 +--
>>>>>> fs/ceph/super.h | 2 +-
>>>>>> fs/file_table.c | 7 +--
>>>>>> fs/fuse/inode.c | 2 +-
>>>>>> fs/nfs/write.c | 2 +-
>>>>>> fs/nfsd/nfscache.c | 2 +-
>>>>>> fs/ntfs/malloc.h | 2 +-
>>>>>> fs/proc/base.c | 2 +-
>>>>>> include/linux/highmem.h | 28 ++++++++++-
>>>>>> include/linux/mm.h | 27 +++++++++-
>>>>>> include/linux/mmzone.h | 15 +++---
>>>>>> include/linux/swap.h | 1 -
>>>>>> kernel/fork.c | 5 +-
>>>>>> kernel/kexec_core.c | 5 +-
>>>>>> kernel/power/snapshot.c | 2 +-
>>>>>> lib/show_mem.c | 2 +-
>>>>>> mm/highmem.c | 4 +-
>>>>>> mm/huge_memory.c | 2 +-
>>>>>> mm/kasan/quarantine.c | 2 +-
>>>>>> mm/memblock.c | 6 +--
>>>>>> mm/memory_hotplug.c | 4 +-
>>>>>> mm/mm_init.c | 2 +-
>>>>>> mm/oom_kill.c | 2 +-
>>>>>> mm/page_alloc.c | 71 +++++++++++++--------------
>>>>>> mm/shmem.c | 7 +--
>>>>>> mm/slab.c | 2 +-
>>>>>> mm/swap.c | 2 +-
>>>>>> mm/util.c | 2 +-
>>>>>> mm/vmalloc.c | 4 +-
>>>>>> mm/vmstat.c | 4 +-
>>>>>> mm/workingset.c | 2 +-
>>>>>> mm/zswap.c | 4 +-
>>>>>> net/dccp/proto.c | 7 +--
>>>>>> net/decnet/dn_route.c | 2 +-
>>>>>> net/ipv4/tcp_metrics.c | 2 +-
>>>>>> net/netfilter/nf_conntrack_core.c | 7 +--
>>>>>> net/netfilter/xt_hashlimit.c | 5 +-
>>>>>> net/sctp/protocol.c | 7 +--
>>>>>> security/integrity/ima/ima_kexec.c | 2 +-
>>>>>> 58 files changed, 195 insertions(+), 144 deletions(-)
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