From: Ralph Campbell <rcampbell@nvidia.com>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"nouveau@lists.freedesktop.org" <nouveau@lists.freedesktop.org>,
"linux-kselftest@vger.kernel.org"
<linux-kselftest@vger.kernel.org>,
Jerome Glisse <jglisse@redhat.com>,
"John Hubbard" <jhubbard@nvidia.com>,
Christoph Hellwig <hch@lst.de>,
Andrew Morton <akpm@linux-foundation.org>,
Ben Skeggs <bskeggs@redhat.com>, Shuah Khan <shuah@kernel.org>
Subject: Re: [PATCH v6 5/6] nouveau: use new mmu interval notifiers
Date: Wed, 19 Feb 2020 17:10:45 -0800 [thread overview]
Message-ID: <770d0aab-726a-12b0-944d-ef71722ad587@nvidia.com> (raw)
In-Reply-To: <20200116202151.GS20978@mellanox.com>
On 1/16/20 12:21 PM, Jason Gunthorpe wrote:
> On Thu, Jan 16, 2020 at 12:16:30PM -0800, Ralph Campbell wrote:
>> Can you point me to the latest ODP code? Seems like my understanding is
>> quite off.
>
> https://elixir.bootlin.com/linux/v5.5-rc6/source/drivers/infiniband/hw/mlx5/odp.c
>
> Look for the word 'implicit'
>
> mlx5_ib_invalidate_range() releases the interval_notifier when there are
> no populated shadow PTEs in its leaf
>
> pagefault_implicit_mr() creates an interval_notifier that covers the
> level in the page table that needs population. Notice it just uses an
> unlocked xa_load to find the page table level.
>
> The locking is pretty tricky as it relies on RCU, but the fault flow
> is fairly lightweight.
>
> Jason
>
Thanks for the information, Jason.
I'm still interested in finding a way to support range based hints to device drivers.
madvise() looks like it only sets a bit in vma->vm_flags or acts on the
advice immediately. mbind() and set_mempolicy() only work with CPUs and memory
with NUMA a node number. What I'm looking for is a way for the device to know
whether to migrate pages to device private memory on a fault, whether to duplicate
read-only pages in device private memory, or remote map/access a page instead of migrating it.
For example, there is a working draft extension to OpenCL,
https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/USM/cl_intel_unified_shared_memory.asciidoc
that could provide a way to specify this sort of advice.
C++ is also looking at extentions for specifying affinity attributes.
In any case, these are probably a long ways off before being finalized and implemented.
I also have some changes to support THP migration to device private memory but that
will require updating nouveau to use 2MB TLB mappings.
In the mean time, I can update the HMM self tests to do something like ODP without
changing mm/mmu_notifier.c but I don't think I can easily change nouveau to that model.
next prev parent reply other threads:[~2020-02-20 1:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-13 22:46 [PATCH v6 0/6] mm/hmm/test: add self tests for HMM Ralph Campbell
2020-01-13 22:46 ` [PATCH v6 1/6] mm/mmu_notifier: add mmu_interval_notifier_insert_safe() Ralph Campbell
2020-01-16 10:07 ` Christoph Hellwig
2020-01-13 22:46 ` [PATCH v6 2/6] mm/mmu_notifier: add mmu_interval_notifier_put() Ralph Campbell
2020-01-13 22:47 ` [PATCH v6 3/6] mm/notifier: add mmu_interval_notifier_update() Ralph Campbell
2020-01-13 22:47 ` [PATCH v6 4/6] mm/mmu_notifier: add mmu_interval_notifier_find() Ralph Campbell
2020-01-14 12:49 ` Jason Gunthorpe
2020-01-15 22:05 ` Ralph Campbell
2020-01-16 14:11 ` Jason Gunthorpe
2020-01-13 22:47 ` [PATCH v6 5/6] nouveau: use new mmu interval notifiers Ralph Campbell
2020-01-14 13:00 ` Jason Gunthorpe
2020-01-15 22:09 ` Ralph Campbell
2020-01-16 16:00 ` Jason Gunthorpe
2020-01-16 20:16 ` Ralph Campbell
2020-01-16 20:21 ` Jason Gunthorpe
2020-02-20 1:10 ` Ralph Campbell [this message]
2020-01-13 22:47 ` [PATCH v6 6/6] mm/hmm/test: add self tests for HMM Ralph Campbell
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