Messages in this thread | | | Date | Wed, 24 Jun 2020 13:00:19 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH v8 1/4] mm/madvise: pass task and mm to do_madvise |
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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-7Tg@mail.gmail.com > > [vbabka@suse.cz: changelog tweak] > [minchan@kernel.org: use current->mm for io_uring] > Link: http://lkml.kernel.org/r/20200423145215.72666-1-minchan@kernel.org > [akpm@linux-foundation.org: fix it for upstream changes] > [akpm@linux-foundation.org: whoops] > [rdunlap@infradead.org: add missing includes] > Link: http://lkml.kernel.org/r/20200302193630.68771-2-minchan@kernel.org > Signed-off-by: Minchan Kim <minchan@kernel.org> > Reviewed-by: Suren Baghdasaryan <surenb@google.com> > Reviewed-by: Vlastimil Babka <vbabka@suse.cz> > Cc: Jens Axboe <axboe@kernel.dk> > Cc: Jann Horn <jannh@google.com> > Cc: Tim Murray <timmurray@google.com> > Cc: Daniel Colascione <dancol@google.com> > Cc: Sandeep Patil <sspatil@google.com> > Cc: Sonny Rao <sonnyrao@google.com> > Cc: Brian Geffon <bgeffon@google.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Shakeel Butt <shakeelb@google.com> > Cc: John Dias <joaodias@google.com> > Cc: Joel Fernandes <joel@joelfernandes.org> > Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> > Cc: SeongJae Park <sj38.park@gmail.com> > Cc: Christian Brauner <christian@brauner.io> > Cc: Kirill Tkhai <ktkhai@virtuozzo.com> > Cc: Oleksandr Natalenko <oleksandr@redhat.com> > Cc: SeongJae Park <sjpark@amazon.de> > Cc: Christian Brauner <christian.brauner@ubuntu.com> > Cc: <linux-man@vger.kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
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