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Reply-To: christian.koenig@amd.com
Subject: Re: [PATCH v4 0/9] mmu notifier provide context informations
To:     Jerome Glisse <jglisse@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org
Cc:     Ralph Campbell <rcampbell@nvidia.com>, Jan Kara <jack@suse.cz>,
        Arnd Bergmann <arnd@arndb.de>, kvm@vger.kernel.org,
        Matthew Wilcox <mawilcox@microsoft.com>,
        linux-rdma@vger.kernel.org, John Hubbard <jhubbard@nvidia.com>,
        Felix Kuehling <Felix.Kuehling@amd.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Michal Hocko <mhocko@kernel.org>,
        Jason Gunthorpe <jgg@mellanox.com>,
        Ross Zwisler <zwisler@kernel.org>,
        linux-fsdevel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Dan Williams <dan.j.williams@intel.com>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
References: <20190123222315.1122-1-jglisse@redhat.com>
 <20190131161006.GA16593@redhat.com>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <ckoenig.leichtzumerken@gmail.com>
Message-ID: <d8c0fd08-c1d9-6035-e5b6-6691874cec07@gmail.com>
Date:   Fri, 1 Feb 2019 13:24:51 +0100
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Am 31.01.19 um 17:10 schrieb Jerome Glisse:
> Andrew what is your plan for this ? I had a discussion with Peter Xu
> and Andrea about change_pte() and kvm. Today the change_pte() kvm
> optimization is effectively disabled because of invalidate_range
> calls. With a minimal couple lines patch on top of this patchset
> we can bring back the kvm change_pte optimization and we can also
> optimize some other cases like for instance when write protecting
> after fork (but i am not sure this is something qemu does often so
> it might not help for real kvm workload).
>
> I will be posting a the extra patch as an RFC, but in the meantime
> i wanted to know what was the status for this.
>
>
> Jan, Christian does your previous ACK still holds for this ?

At least the general approach still sounds perfectly sane to me.

Regarding how to merge these patches I think we should just get the 
general infrastructure into Linus tree and when can then merge the DRM 
patches one release later when we are sure that it doesn't break anything.

Christian.

>
>
> On Wed, Jan 23, 2019 at 05:23:06PM -0500, jglisse@redhat.com wrote:
>> From: Jérôme Glisse <jglisse@redhat.com>
>>
>> Hi Andrew, i see that you still have my event patch in you queue [1].
>> This patchset replace that single patch and is broken down in further
>> step so that it is easier to review and ascertain that no mistake were
>> made during mechanical changes. Here are the step:
>>
>>      Patch 1 - add the enum values
>>      Patch 2 - coccinelle semantic patch to convert all call site of
>>                mmu_notifier_range_init to default enum value and also
>>                to passing down the vma when it is available
>>      Patch 3 - update many call site to more accurate enum values
>>      Patch 4 - add the information to the mmu_notifier_range struct
>>      Patch 5 - helper to test if a range is updated to read only
>>
>> All the remaining patches are update to various driver to demonstrate
>> how this new information get use by device driver. I build tested
>> with make all and make all minus everything that enable mmu notifier
>> ie building with MMU_NOTIFIER=no. Also tested with some radeon,amd
>> gpu and intel gpu.
>>
>> If they are no objections i believe best plan would be to merge the
>> the first 5 patches (all mm changes) through your queue for 5.1 and
>> then to delay driver update to each individual driver tree for 5.2.
>> This will allow each individual device driver maintainer time to more
>> thouroughly test this more then my own testing.
>>
>> Note that i also intend to use this feature further in nouveau and
>> HMM down the road. I also expect that other user like KVM might be
>> interested into leveraging this new information to optimize some of
>> there secondary page table invalidation.
>>
>> Here is an explaination on the rational for this patchset:
>>
>>
>> CPU page table update can happens for many reasons, not only as a result
>> of a syscall (munmap(), mprotect(), mremap(), madvise(), ...) but also
>> as a result of kernel activities (memory compression, reclaim, migration,
>> ...).
>>
>> This patch introduce a set of enums that can be associated with each of
>> the events triggering a mmu notifier. Latter patches take advantages of
>> those enum values.
>>
>> - UNMAP: munmap() or mremap()
>> - CLEAR: page table is cleared (migration, compaction, reclaim, ...)
>> - PROTECTION_VMA: change in access protections for the range
>> - PROTECTION_PAGE: change in access protections for page in the range
>> - SOFT_DIRTY: soft dirtyness tracking
>>
>> Being able to identify munmap() and mremap() from other reasons why the
>> page table is cleared is important to allow user of mmu notifier to
>> update their own internal tracking structure accordingly (on munmap or
>> mremap it is not longer needed to track range of virtual address as it
>> becomes invalid).
>>
>> [1] https://www.ozlabs.org/~akpm/mmotm/broken-out/mm-mmu_notifier-contextual-information-for-event-triggering-invalidation-v2.patch
>>
>> Cc: Christian König <christian.koenig@amd.com>
>> Cc: Jan Kara <jack@suse.cz>
>> Cc: Felix Kuehling <Felix.Kuehling@amd.com>
>> Cc: Jason Gunthorpe <jgg@mellanox.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Matthew Wilcox <mawilcox@microsoft.com>
>> Cc: Ross Zwisler <zwisler@kernel.org>
>> Cc: Dan Williams <dan.j.williams@intel.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Ralph Campbell <rcampbell@nvidia.com>
>> Cc: John Hubbard <jhubbard@nvidia.com>
>> Cc: kvm@vger.kernel.org
>> Cc: dri-devel@lists.freedesktop.org
>> Cc: linux-rdma@vger.kernel.org
>> Cc: linux-fsdevel@vger.kernel.org
>> Cc: Arnd Bergmann <arnd@arndb.de>
>>
>> Jérôme Glisse (9):
>>    mm/mmu_notifier: contextual information for event enums
>>    mm/mmu_notifier: contextual information for event triggering
>>      invalidation
>>    mm/mmu_notifier: use correct mmu_notifier events for each invalidation
>>    mm/mmu_notifier: pass down vma and reasons why mmu notifier is
>>      happening
>>    mm/mmu_notifier: mmu_notifier_range_update_to_read_only() helper
>>    gpu/drm/radeon: optimize out the case when a range is updated to read
>>      only
>>    gpu/drm/amdgpu: optimize out the case when a range is updated to read
>>      only
>>    gpu/drm/i915: optimize out the case when a range is updated to read
>>      only
>>    RDMA/umem_odp: optimize out the case when a range is updated to read
>>      only
>>
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c  | 13 ++++++++
>>   drivers/gpu/drm/i915/i915_gem_userptr.c | 16 ++++++++++
>>   drivers/gpu/drm/radeon/radeon_mn.c      | 13 ++++++++
>>   drivers/infiniband/core/umem_odp.c      | 22 +++++++++++--
>>   fs/proc/task_mmu.c                      |  3 +-
>>   include/linux/mmu_notifier.h            | 42 ++++++++++++++++++++++++-
>>   include/rdma/ib_umem_odp.h              |  1 +
>>   kernel/events/uprobes.c                 |  3 +-
>>   mm/huge_memory.c                        | 14 +++++----
>>   mm/hugetlb.c                            | 11 ++++---
>>   mm/khugepaged.c                         |  3 +-
>>   mm/ksm.c                                |  6 ++--
>>   mm/madvise.c                            |  3 +-
>>   mm/memory.c                             | 25 +++++++++------
>>   mm/migrate.c                            |  5 ++-
>>   mm/mmu_notifier.c                       | 10 ++++++
>>   mm/mprotect.c                           |  4 ++-
>>   mm/mremap.c                             |  3 +-
>>   mm/oom_kill.c                           |  3 +-
>>   mm/rmap.c                               |  6 ++--
>>   20 files changed, 171 insertions(+), 35 deletions(-)
>>
>> -- 
>> 2.17.2
>>
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