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From: Michal Hocko <mhocko@suse.com>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: David Hildenbrand <david@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux-MM <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Peter Xu <peterx@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Minchan Kim <minchan@kernel.org>, Colin Cross <ccross@google.com>,
	Suren Baghdasarya <surenb@google.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 0/8] mm/madvise: support process_madvise(MADV_DONTNEED)
Date: Mon, 27 Sep 2021 14:16:12 +0200	[thread overview]
Message-ID: <YVG2DJx9t6FGr4kX@dhcp22.suse.cz> (raw)
In-Reply-To: <AE756194-07D4-4467-92CA-9E986140D85D@gmail.com>

On Mon 27-09-21 05:00:11, Nadav Amit wrote:
[...]
> The manager is notified on memory regions that it should monitor
> (through PTRACE/LD_PRELOAD/explicit-API). It then monitors these regions
> using the remote-userfaultfd that you saw on the second thread. When it wants
> to reclaim (anonymous) memory, it:
> 
> 1. Uses UFFD-WP to protect that memory (and for this matter I got a vectored
>    UFFD-WP to do so efficiently, a patch which I did not send yet).
> 2. Calls process_vm_readv() to read that memory of that process.
> 3. Write it back to “swap”.
> 4. Calls process_madvise(MADV_DONTNEED) to zap it.

Why cannot you use MADV_PAGEOUT/MADV_COLD for this usecase?

MADV_DONTNEED on a remote process has been proposed in the past several
times and it has always been rejected because it is a free ticket to all
sorts of hard to debug problems as it is just a free ticket for a remote
memory corruption. An additional capability requirement might reduce the
risk to some degree but I still do not think this is a good idea.
-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2021-09-27 12:16 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-26 16:12 [RFC PATCH 0/8] mm/madvise: support process_madvise(MADV_DONTNEED) Nadav Amit
2021-09-26 16:12 ` [RFC PATCH 1/8] mm/madvise: propagate vma->vm_end changes Nadav Amit
2021-09-27  9:08   ` Kirill A. Shutemov
2021-09-27 10:11     ` Nadav Amit
2021-09-27 11:55       ` Kirill A. Shutemov
2021-09-27 12:33         ` Nadav Amit
2021-09-27 12:45           ` Kirill A. Shutemov
2021-09-27 12:59             ` Nadav Amit
2021-09-26 16:12 ` [RFC PATCH 2/8] mm/madvise: remove unnecessary check on madvise_dontneed_free() Nadav Amit
2021-09-27  9:11   ` Kirill A. Shutemov
2021-09-27 11:05     ` Nadav Amit
2021-09-27 12:19       ` Kirill A. Shutemov
2021-09-27 12:52         ` Nadav Amit
2021-09-26 16:12 ` [RFC PATCH 3/8] mm/madvise: remove unnecessary checks on madvise_free_single_vma() Nadav Amit
2021-09-27  9:17   ` Kirill A. Shutemov
2021-09-27  9:24     ` Kirill A. Shutemov
2021-09-26 16:12 ` [RFC PATCH 4/8] mm/madvise: define madvise behavior in a struct Nadav Amit
2021-09-27  9:31   ` Kirill A. Shutemov
2021-09-27 10:31     ` Nadav Amit
2021-09-27 12:14       ` Kirill A. Shutemov
2021-09-27 20:36         ` Nadav Amit
2021-09-26 16:12 ` [RFC PATCH 5/8] mm/madvise: perform certain operations once on process_madvise() Nadav Amit
2021-09-26 16:12 ` [RFC PATCH 6/8] mm/madvise: more aggressive TLB batching Nadav Amit
2021-09-26 16:12 ` [RFC PATCH 7/8] mm/madvise: deduplicate code in madvise_dontneed_free() Nadav Amit
2021-09-26 16:12 ` [RFC PATCH 8/8] mm/madvise: process_madvise(MADV_DONTNEED) Nadav Amit
2021-09-27  9:24 ` [RFC PATCH 0/8] mm/madvise: support process_madvise(MADV_DONTNEED) David Hildenbrand
2021-09-27 10:41   ` Nadav Amit
2021-09-27 10:58     ` David Hildenbrand
2021-09-27 12:00       ` Nadav Amit
2021-09-27 12:16         ` Michal Hocko [this message]
2021-09-27 19:12           ` Nadav Amit
2021-09-29  7:52             ` Michal Hocko
2021-09-29 18:31               ` Nadav Amit
2021-10-12 23:14                 ` Peter Xu
2021-10-13 15:47                   ` Nadav Amit
2021-10-13 23:09                     ` Peter Xu
2021-09-27 17:05         ` David Hildenbrand
2021-09-27 19:59           ` Nadav Amit
2021-09-28  8:53             ` David Hildenbrand
2021-09-28 22:56               ` Nadav Amit
2021-10-04 17:58                 ` David Hildenbrand
2021-10-07 16:19                   ` Nadav Amit
2021-10-07 16:46                     ` David Hildenbrand

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