Messages in this thread | | | Date | Fri, 28 Apr 2017 14:00:06 -0400 (EDT) | From | Jerome Glisse <> | Subject | Re: [PATCH v2] mm, zone_device: replace {get, put}_zone_device_page() with a single reference |
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> On Fri, Apr 28, 2017 at 10:34 AM, Jerome Glisse <jglisse@redhat.com> wrote: > >> Kirill points out that the calls to {get,put}_dev_pagemap() can be > >> removed from the mm fast path if we take a single get_dev_pagemap() > >> reference to signify that the page is alive and use the final put of the > >> page to drop that reference. > >> > >> This does require some care to make sure that any waits for the > >> percpu_ref to drop to zero occur *after* devm_memremap_page_release(), > >> since it now maintains its own elevated reference. > > > > This is NAK from HMM point of view as i need those call. So if you remove > > them now i will need to add them back as part of HMM. > > I thought you only need them at page free time? You can still hook > __put_page().
No, i need a hook when page refcount reach 1, not 0. That being said i don't care about put_dev_pagemap(page->pgmap); so that part of the patch is fine from HMM point of view but i definitly need to hook my- self in the general put_page() function.
So i will have to undo part of this patch for HMM (put_page() will need to handle ZONE_DEVICE page differently).
Cheers, Jérôme
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