On Mon, 22 Jun 2020, Minchan Kim wrote:
> Patch series "introduce memory hinting API for external process", v8.
>
> Now, we have MADV_PAGEOUT and MADV_COLD as madvise hinting API. With
> that, application could give hints to kernel what memory range are
> preferred to be reclaimed. However, in some platform(e.g., Android), the
> information required to make the hinting decision is not known to the app.
> Instead, it is known to a centralized userspace daemon(e.g.,
> ActivityManagerService), and that daemon must be able to initiate reclaim
> on its own without any app involvement.
>
> To solve the concern, this patch introduces new syscall -
> process_madvise(2). Bascially, it's same with madvise(2) syscall but it
> has some differences.
>
> 1. It needs pidfd of target process to provide the hint
>
> 2. It supports only MADV_{COLD|PAGEOUT|MERGEABLE|UNMEREABLE} at this
> moment. Other hints in madvise will be opened when there are explicit
> requests from community to prevent unexpected bugs we couldn't support.
>
> 3. Only privileged processes can do something for other process's
> address space.
>
> For more detail of the new API, please see "mm: introduce external memory
> hinting API" description in this patchset.
>
> This patch (of 4):
>
> In upcoming patches, do_madvise will be called from external process
> context so we shouldn't asssume "current" is always hinted process's
> task_struct.
>
> Furthermore, we must not access mm_struct via task->mm, but obtain it
> via access_mm() once (in the following patch) and only use that pointer
> [1], so pass it to do_madvise() as well. Note the vma->vm_mm pointers
> are safe, so we can use them further down the call stack.
>
> And let's pass *current* and current->mm as arguments of do_madvise so
> it shouldn't change existing behavior but prepare next patch to make
> review easy.
>
> Note: io_madvise passes NULL as target_task argument of do_madvise because
> it couldn't know who is target.
>
> [1]
> http://lore.kernel.org/r/CAG48ez27=pwm5m_n_988xt1huo7g7h6artql44zev6td-h-...@mail.gmail.com
>
> [vba...@suse.cz: changelog tweak]
> [minc...@kernel.org: use current->mm for io_uring]
> Link: http://lkml.kernel.org/r/20200423145215.72666-1-minc...@kernel.org
> [a...@linux-foundation.org: fix it for upstream changes]
> [a...@linux-foundation.org: whoops]
> [rdun...@infradead.org: add missing includes]
> Link: http://lkml.kernel.org/r/20200302193630.68771-2-minc...@kernel.org
> Signed-off-by: Minchan Kim <minc...@kernel.org>
> Reviewed-by: Suren Baghdasaryan <sur...@google.com>
> Reviewed-by: Vlastimil Babka <vba...@suse.cz>
> Cc: Jens Axboe <ax...@kernel.dk>
> Cc: Jann Horn <ja...@google.com>
> Cc: Tim Murray <timmur...@google.com>
> Cc: Daniel Colascione <dan...@google.com>
> Cc: Sandeep Patil <sspa...@google.com>
> Cc: Sonny Rao <sonny...@google.com>
> Cc: Brian Geffon <bgef...@google.com>
> Cc: Michal Hocko <mho...@suse.com>
> Cc: Johannes Weiner <han...@cmpxchg.org>
> Cc: Shakeel Butt <shake...@google.com>
> Cc: John Dias <joaod...@google.com>
> Cc: Joel Fernandes <j...@joelfernandes.org>
> Cc: Alexander Duyck <alexander.h.du...@linux.intel.com>
> Cc: SeongJae Park <sj38.p...@gmail.com>
> Cc: Christian Brauner <christ...@brauner.io>
> Cc: Kirill Tkhai <ktk...@virtuozzo.com>
> Cc: Oleksandr Natalenko <oleksa...@redhat.com>
> Cc: SeongJae Park <sjp...@amazon.de>
> Cc: Christian Brauner <christian.brau...@ubuntu.com>
> Cc: <linux-...@vger.kernel.org>
Acked-by: David Rientjes <rient...@google.com>
