From: Felix Kuehling <felix.kuehling@amd.com> To: David Hildenbrand <david@redhat.com>, Alex Sierra <alex.sierra@amd.com>, jgg@nvidia.com Cc: linux-mm@kvack.org, rcampbell@nvidia.com, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, hch@lst.de, jglisse@redhat.com, apopple@nvidia.com, willy@infradead.org, akpm@linux-foundation.org Subject: Re: [PATCH v1 1/3] mm: split vm_normal_pages for LRU and non-LRU handling Date: Fri, 11 Mar 2022 12:08:05 -0500 [thread overview] Message-ID: <1747447c-202d-9195-9d44-57f299be48c4@amd.com> (raw) In-Reply-To: <07401a0a-6878-6af2-f663-9f0c3c1d88e5@redhat.com> On 2022-03-11 04:16, David Hildenbrand wrote: > On 10.03.22 18:26, Alex Sierra wrote: >> DEVICE_COHERENT pages introduce a subtle distinction in the way >> "normal" pages can be used by various callers throughout the kernel. >> They behave like normal pages for purposes of mapping in CPU page >> tables, and for COW. But they do not support LRU lists, NUMA >> migration or THP. Therefore we split vm_normal_page into two >> functions vm_normal_any_page and vm_normal_lru_page. The latter will >> only return pages that can be put on an LRU list and that support >> NUMA migration, KSM and THP. >> >> We also introduced a FOLL_LRU flag that adds the same behaviour to >> follow_page and related APIs, to allow callers to specify that they >> expect to put pages on an LRU list. >> > I still don't see the need for s/vm_normal_page/vm_normal_any_page/. And > as this patch is dominated by that change, I'd suggest (again) to just > drop it as I don't see any value of that renaming. No specifier implies any. OK. If nobody objects, we can adopts that naming convention. > > The general idea of this change LGTM. > > > I wonder how this interacts with the actual DEVICE_COHERENT coherent > series. Is this a preparation? Should it be part of the DEVICE_COHERENT > series? Yes, it should be part of that series. Alex developed it on top of the series for now. But I think eventually it would need to be spliced into it. Patch1 would need to go somewhere before the other DEVICE_COHERENT patches (with minor modifications). Patch 2 could be squashed into "tools: add hmm gup test for long term pinned device pages" or go next to it. Patch 3 doesn't have a direct dependency on device-coherent pages. It only mentions them in comments. > > IOW, should this patch start with > > "With DEVICE_COHERENT, we'll soon have vm_normal_pages() return > device-managed anonymous pages that are not LRU pages. Although they > behave like normal pages for purposes of mapping in CPU page, and for > COW, they do not support LRU lists, NUMA migration or THP. [...]" Yes, that makes sense. Regards, Felix > > But then, I'm confused by patch 2 and 3, because it feels more like we'd > already have DEVICE_COHERENT then ("hmm_is_coherent_type"). > >
WARNING: multiple messages have this Message-ID (diff)
From: Felix Kuehling <felix.kuehling@amd.com> To: David Hildenbrand <david@redhat.com>, Alex Sierra <alex.sierra@amd.com>, jgg@nvidia.com Cc: rcampbell@nvidia.com, willy@infradead.org, apopple@nvidia.com, dri-devel@lists.freedesktop.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com, amd-gfx@lists.freedesktop.org, akpm@linux-foundation.org, linux-ext4@vger.kernel.org, hch@lst.de Subject: Re: [PATCH v1 1/3] mm: split vm_normal_pages for LRU and non-LRU handling Date: Fri, 11 Mar 2022 12:08:05 -0500 [thread overview] Message-ID: <1747447c-202d-9195-9d44-57f299be48c4@amd.com> (raw) In-Reply-To: <07401a0a-6878-6af2-f663-9f0c3c1d88e5@redhat.com> On 2022-03-11 04:16, David Hildenbrand wrote: > On 10.03.22 18:26, Alex Sierra wrote: >> DEVICE_COHERENT pages introduce a subtle distinction in the way >> "normal" pages can be used by various callers throughout the kernel. >> They behave like normal pages for purposes of mapping in CPU page >> tables, and for COW. But they do not support LRU lists, NUMA >> migration or THP. Therefore we split vm_normal_page into two >> functions vm_normal_any_page and vm_normal_lru_page. The latter will >> only return pages that can be put on an LRU list and that support >> NUMA migration, KSM and THP. >> >> We also introduced a FOLL_LRU flag that adds the same behaviour to >> follow_page and related APIs, to allow callers to specify that they >> expect to put pages on an LRU list. >> > I still don't see the need for s/vm_normal_page/vm_normal_any_page/. And > as this patch is dominated by that change, I'd suggest (again) to just > drop it as I don't see any value of that renaming. No specifier implies any. OK. If nobody objects, we can adopts that naming convention. > > The general idea of this change LGTM. > > > I wonder how this interacts with the actual DEVICE_COHERENT coherent > series. Is this a preparation? Should it be part of the DEVICE_COHERENT > series? Yes, it should be part of that series. Alex developed it on top of the series for now. But I think eventually it would need to be spliced into it. Patch1 would need to go somewhere before the other DEVICE_COHERENT patches (with minor modifications). Patch 2 could be squashed into "tools: add hmm gup test for long term pinned device pages" or go next to it. Patch 3 doesn't have a direct dependency on device-coherent pages. It only mentions them in comments. > > IOW, should this patch start with > > "With DEVICE_COHERENT, we'll soon have vm_normal_pages() return > device-managed anonymous pages that are not LRU pages. Although they > behave like normal pages for purposes of mapping in CPU page, and for > COW, they do not support LRU lists, NUMA migration or THP. [...]" Yes, that makes sense. Regards, Felix > > But then, I'm confused by patch 2 and 3, because it feels more like we'd > already have DEVICE_COHERENT then ("hmm_is_coherent_type"). > >
next prev parent reply other threads:[~2022-03-11 17:08 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-03-10 17:26 [PATCH v1 0/3] split vm_normal_pages for LRU and non-LRU handling Alex Sierra 2022-03-10 17:26 ` Alex Sierra 2022-03-10 17:26 ` [PATCH v1 1/3] mm: " Alex Sierra 2022-03-10 17:26 ` Alex Sierra 2022-03-10 19:25 ` Matthew Wilcox 2022-03-10 19:25 ` Matthew Wilcox 2022-03-10 21:58 ` Felix Kuehling 2022-03-10 21:58 ` Felix Kuehling 2022-03-17 2:50 ` Alistair Popple 2022-03-17 2:50 ` Alistair Popple 2022-03-11 9:16 ` David Hildenbrand 2022-03-11 9:16 ` David Hildenbrand 2022-03-11 17:08 ` Felix Kuehling [this message] 2022-03-11 17:08 ` Felix Kuehling 2022-03-17 2:54 ` Alistair Popple 2022-03-17 2:54 ` Alistair Popple 2022-03-17 8:13 ` David Hildenbrand 2022-03-17 8:13 ` David Hildenbrand 2022-03-17 13:25 ` Jason Gunthorpe 2022-03-17 13:25 ` Jason Gunthorpe 2022-03-10 17:26 ` [PATCH v1 2/3] tools: add more gup configs to hmm_gup selftests Alex Sierra 2022-03-10 17:26 ` Alex Sierra 2022-03-10 17:26 ` [PATCH v1 3/3] tools: add selftests to hmm for COW in device memory Alex Sierra 2022-03-10 17:26 ` Alex Sierra
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