From: Nadav Amit <nadav.amit@gmail.com>
To: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, 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 03:41:18 -0700 [thread overview]
Message-ID: <6E8A03DD-175F-4A21-BCD7-383D61344521@gmail.com> (raw)
In-Reply-To: <7ce823c8-cfbf-cc59-9fc7-9aa3a79740c3@redhat.com>
> On Sep 27, 2021, at 2:24 AM, David Hildenbrand <david@redhat.com> wrote:
>
> On 26.09.21 18:12, Nadav Amit wrote:
>> From: Nadav Amit <namit@vmware.com>
>> The goal of these patches is to add support for
>> process_madvise(MADV_DONTNEED). Yet, in the process some (arguably)
>> useful cleanups, a bug fix and performance enhancements are performed.
>> The patches try to consolidate the logic across different behaviors, and
>> to a certain extent overlap/conflict with an outstanding patch that does
>> something similar [1]. This consolidation however is mostly orthogonal
>> to the aforementioned one and done in order to clarify what is done in
>> respect to locks and TLB for each behavior and to batch these operations
>> more efficiently on process_madvise().
>> process_madvise(MADV_DONTNEED) is useful for two reasons: (a) it allows
>> userfaultfd monitors to unmap memory from monitored processes; and (b)
>> it is more efficient than madvise() since it is vectored and batches TLB
>> flushes more aggressively.
>
> MADV_DONTNEED on MAP_PRIVATE memory is a target-visible operation; this is very different to all the other process_madvise() calls we allow, which are merely hints, but the target cannot be broken . I don't think this is acceptable.
This is a fair point, which I expected, but did not address properly.
I guess an additional capability, such as CAP_SYS_PTRACE needs to be
required in this case. Would that ease your mind?
next prev parent reply other threads:[~2021-09-27 10:41 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-26 16:12 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 [this message]
2021-09-27 10:58 ` David Hildenbrand
2021-09-27 12:00 ` Nadav Amit
2021-09-27 12:16 ` Michal Hocko
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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