From: Peter Xu <peterx@redhat.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: peterx@redhat.com, Jason Gunthorpe <jgg@ziepe.ca>,
John Hubbard <jhubbard@nvidia.com>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@lst.de>, Yang Shi <shy828301@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
Kirill Tkhai <ktkhai@virtuozzo.com>,
Kirill Shutemov <kirill@shutemov.name>,
Hugh Dickins <hughd@google.com>, Jann Horn <jannh@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>, Jan Kara <jack@suse.cz>,
Andrea Arcangeli <aarcange@redhat.com>,
Leon Romanovsky <leonro@nvidia.com>
Subject: [PATCH v2 0/4] mm: Break COW for pinned pages during fork()
Date: Fri, 25 Sep 2020 18:25:56 -0400 [thread overview]
Message-ID: <20200925222600.6832-1-peterx@redhat.com> (raw)
Due to the rebase to latest rc6, the major pte copy patch changed a lot. So
maybe not that useful to write a changelog any more. However all the comments
should be addressed as long as discussed in previous thread. Please shoot if I
missed anything important.
This series is majorly inspired by the previous discussion on the list [1],
starting from the report from Jason on the rdma test failure. Linus proposed
the solution, which seems to be a very nice approach to avoid the breakage of
userspace apps that didn't use MADV_DONTFORK properly before. More information
can be found in that thread too.
I tested it myself with fork() after vfio pinning a bunch of device pages, and
I verified that the new copy pte logic worked as expected at least in the most
general path. However I didn't test thp case yet because afaict vfio does not
support thp backed dma pages. Luckily, the pmd/pud thp patch is much more
straightforward than the pte one, so hopefully it can be directly verified by
some code review plus some more heavy-weight rdma tests.
Patch 1: Introduce mm.has_pinned
Patch 2: Preparation patch
Patch 3: Early cow solution for pte copy for pinned pages
Patch 4: Same as above, but for thp (pmd/pud).
Hugetlbfs fix is still missing, but as planned, that's not urgent so we can
work upon. Comments greatly welcomed.
[1] https://lore.kernel.org/lkml/20200914143829.GA1424636@nvidia.com/
Thanks.
Peter Xu (4):
mm: Introduce mm_struct.has_pinned
mm/fork: Pass new vma pointer into copy_page_range()
mm: Do early cow for pinned pages during fork() for ptes
mm/thp: Split huge pmds/puds if they're pinned when fork()
include/linux/mm.h | 2 +-
include/linux/mm_types.h | 10 +++
kernel/fork.c | 3 +-
mm/gup.c | 6 ++
mm/huge_memory.c | 28 ++++++
mm/memory.c | 186 ++++++++++++++++++++++++++++++++++-----
6 files changed, 212 insertions(+), 23 deletions(-)
--
2.26.2
next reply other threads:[~2020-09-25 22:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-25 22:25 Peter Xu [this message]
2020-09-25 22:25 ` [PATCH v2 1/4] mm: Introduce mm_struct.has_pinned Peter Xu
2020-09-25 22:25 ` [PATCH v2 2/4] mm/fork: Pass new vma pointer into copy_page_range() Peter Xu
2020-09-30 13:30 ` Kirill A. Shutemov
2020-09-30 17:05 ` Peter Xu
2020-09-25 22:25 ` [PATCH v2 3/4] mm: Do early cow for pinned pages during fork() for ptes Peter Xu
2020-09-26 23:23 ` Jason Gunthorpe
2020-09-27 0:04 ` Linus Torvalds
2020-09-25 22:26 ` [PATCH v2 4/4] mm/thp: Split huge pmds/puds if they're pinned when fork() Peter Xu
2020-09-27 19:35 ` [PATCH v2 0/4] mm: Break COW for pinned pages during fork() Linus Torvalds
2020-09-29 11:02 ` Leon Romanovsky
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