From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: John Hubbard <jhubbard@nvidia.com>
Cc: akpm@linux-foundation.org, Andrea Arcangeli <aarcange@redhat.com>,
Zi Yan <ziy@nvidia.com>, Yang Shi <yang.shi@linux.alibaba.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCHv2 5/8] khugepaged: Allow to callapse a page shared across fork
Date: Mon, 13 Apr 2020 12:42:04 +0300 [thread overview]
Message-ID: <20200413094204.a2gpsjhugy5dznjy@box> (raw)
In-Reply-To: <df772934-b5e5-8578-9b47-3f17bf9b8896@nvidia.com>
On Fri, Apr 10, 2020 at 01:59:22PM -0700, John Hubbard wrote:
> I think I understood what you were saying. The problem is that was ignoring
> a couple of points, especially in an RDMA situation: 1) the page can be
> pinned by various drivers, on behalf of other processes, even if the original
> process is being torn down, and 2) it doesn't really matter which process pins
> a page--the end result is that it's pinned.
Well, no. It is critical that nobody gets new pins after this point on
behalf of *this* process as we about change what is mapped on this virtual
address range. We must avoid the situation that khugepaged screws
legitimate GUP users and make what process see differs from what GUP see.
Pins on behalf of other processes after the point are not relevant to us.
I will keep the comment as is for now. As you can see I'm struggling
communicating my point. Any better wording is welcome.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-04-13 9:49 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-03 11:29 [PATCHv2 0/8] thp/khugepaged improvements and CoW semantics Kirill A. Shutemov
2020-04-03 11:29 ` [PATCHv2 1/8] khugepaged: Add self test Kirill A. Shutemov
2020-04-06 14:59 ` Zi Yan
2020-04-06 15:20 ` Kirill A. Shutemov
2020-04-06 18:50 ` Zi Yan
2020-04-08 14:21 ` Kirill A. Shutemov
2020-04-08 15:53 ` Zi Yan
2020-04-10 11:47 ` Kirill A. Shutemov
2020-04-10 14:36 ` Zi Yan
2020-04-10 14:58 ` Kirill A. Shutemov
2020-04-10 15:03 ` Zi Yan
2020-04-06 18:53 ` Ralph Campbell
2020-04-03 11:29 ` [PATCHv2 2/8] khugepaged: Do not stop collapse if less than half PTEs are referenced Kirill A. Shutemov
2020-04-06 18:13 ` Yang Shi
2020-04-06 19:53 ` Ralph Campbell
2020-04-09 13:34 ` Kirill A. Shutemov
2020-04-03 11:29 ` [PATCHv2 3/8] khugepaged: Drain all LRU caches before scanning pages Kirill A. Shutemov
2020-04-06 18:15 ` Yang Shi
2020-04-03 11:29 ` [PATCHv2 4/8] khugepaged: Drain LRU add pagevec after swapin Kirill A. Shutemov
2020-04-06 13:11 ` Zi Yan
2020-04-06 18:29 ` Yang Shi
2020-04-08 13:05 ` Kirill A. Shutemov
2020-04-08 18:42 ` Yang Shi
2020-04-03 11:29 ` [PATCHv2 5/8] khugepaged: Allow to callapse a page shared across fork Kirill A. Shutemov
2020-04-06 20:15 ` Ralph Campbell
2020-04-06 20:50 ` Yang Shi
2020-04-08 13:10 ` Kirill A. Shutemov
2020-04-08 18:51 ` Yang Shi
2020-04-10 0:03 ` Yang Shi
2020-04-10 15:56 ` Kirill A. Shutemov
2020-04-06 21:30 ` John Hubbard
2020-04-10 15:55 ` Kirill A. Shutemov
2020-04-10 20:59 ` John Hubbard
2020-04-13 9:42 ` Kirill A. Shutemov [this message]
2020-04-03 11:29 ` [PATCHv2 6/8] khugepaged: Allow to collapse PTE-mapped compound pages Kirill A. Shutemov
2020-04-06 21:29 ` Yang Shi
2020-04-08 13:29 ` Kirill A. Shutemov
2020-04-08 18:57 ` Yang Shi
2020-04-09 13:47 ` Kirill A. Shutemov
2020-04-03 11:29 ` [PATCHv2 7/8] thp: Change CoW semantics for anon-THP Kirill A. Shutemov
2020-04-07 7:57 ` [thp] db001b7115: vm-scalability.median 8.9% improvement kernel test robot
2020-04-07 7:57 ` kernel test robot
2020-04-03 11:29 ` [PATCHv2 8/8] khugepaged: Introduce 'max_ptes_shared' tunable Kirill A. Shutemov
2020-04-06 13:17 ` Zi Yan
2020-04-05 23:40 ` [PATCHv2 0/8] thp/khugepaged improvements and CoW semantics William Kucharski
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