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b=MXeSpvzNZH3neEpfIqeBYyTuGrfYdNqTJ2UNkCyomcsiNhfK7p03iX8EBK4XpNHxN q2WMUdjTYcnkaHDpSUg6Aj0cXvEyLymTab+z1UuQhpxQo+aplU98X18LEMW9D4xfOm 6IIrG145K0vpUS9w6ydRaHBJu9zzOfbo6JW17Oeo= Date: Wed, 23 Oct 2024 19:22:29 -0700 From: Andrew Morton To: Matthew Brost Cc: , , , , , , Subject: Re: [PATCH v3 1/1] mm/migrate: Add migrate_device_pfns Message-Id: <20241023192229.64333482554de0135397cb23@linux-foundation.org> In-Reply-To: References: <20241023233944.1798835-1-matthew.brost@intel.com> <20241023233944.1798835-2-matthew.brost@intel.com> <20241023182217.147ee87197b53d47057a4c06@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 369631A0012 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: fiejzuqtwgktoupoj3hrxwudbsu8ys7r X-HE-Tag: 1729736529-345087 X-HE-Meta: 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 XilDSXD2 wt4ZF5B+xiqr0E7FjHtNck55cUo3n+OiFsb35wMce83rd36Np/AV4wYRz7YKeNZy0+PwAaZCGq+hPkzZoZewYa77R0L7CeRT+V/Qm/8o6l5OV2JON9/ZXgExZkdCWd3UPgoHJ1Y+qlOSBQxYPdZRyrIwr2cTThSzg2U2x5x4ov53RpixfM+ACWdQAPs1YxIr48yxm+nVbmO1/bI9EL7nOzLFnYdzCrkGhmUt6Apsj0RrGy3cVJz4JCeAKk+6FI2f7MAJGfRvOaYglHkOCGxqyhTOecw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 24 Oct 2024 01:50:34 +0000 Matthew Brost wrote: > > On Wed, 23 Oct 2024 16:39:44 -0700 Matthew Brost wrote: > > > > > Implement migrate_device_pfns to prepare an array of PFNs for migration. > > > Handles non-contiguous ranges of device pages that require migration. > > > > OK, that's "what". We're more interested in "why". > > > > Sure can add. The 'why' is: > > A non-contiguous allocation of device pages can occur if a device is > under memory pressure within a single driver allocation of device > memory. Additionally, a driver allocation of memory can also be evicted > under memory pressure. Therefore, an interface for migrating a set of > non-contiguous device pages is required. OK, thanks. But when merging a new interface such as this we like to see the code which will actually use the interface. Along with reasons to believe that the calling code will actually be merged, so we don't end up with a new interface which has no callers. Apart from that, I suspect that it makes more sense to merge this via the DRM tree, alongside the code which uses it.