From: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Michel Lespinasse <michel@lespinasse.org>,
Joel Fernandes <joelaf@google.com>,
Song Liu <songliubraving@fb.com>,
David Hildenbrand <david@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Peter Xu <peterx@redhat.com>,
dhowells@redhat.com, linux-mm <linux-mm@kvack.org>,
Jerome Glisse <jglisse@google.com>,
Davidlohr Bueso <dave@stgolabs.net>,
Minchan Kim <minchan@google.com>,
x86@kernel.org, Hugh Dickins <hughd@google.com>,
Matthew Wilcox <willy@infradead.org>,
Laurent Dufour <laurent.dufour@fr.ibm.com>,
Mel Gorman <mgorman@suse.de>,
David Rientjes <rientjes@google.com>,
Axel Rasmussen <axelrasmussen@google.com>,
kernel-team <kernel-team@android.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
"Liam R. Howlett" <liam.howlett@oracle.com>,
Andy Lutomirski <luto@kernel.org>,
Laurent Dufour <ldufour@linux.ibm.com>,
Vlastimil Babka <vbabka@suse.cz>,
linux-arm-kernel@lists.infradead.org,
Kent Overstreet <kent.overstreet@linux.dev>,
LKML <linux-kernel@vger.kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC PATCH RESEND 00/28] per-VMA locks proposal
Date: Mon, 5 Sep 2022 11:32:48 -0700 [thread overview]
Message-ID: <CAJuCfpG3bMLzNhP5wt8my8j7_9wW=darLegd6WPV6tddtCKGAA@mail.gmail.com> (raw)
In-Reply-To: <YxXsQKoQ0URIRuKi@dhcp22.suse.cz>
On Mon, Sep 5, 2022 at 5:32 AM 'Michal Hocko' via kernel-team
<kernel-team@android.com> wrote:
>
> Unless I am missing something, this is not based on the Maple tree
> rewrite, right? Does the change in the data structure makes any
> difference to the approach? I remember discussions at LSFMM where it has
> been pointed out that some issues with the vma tree are considerably
> simpler to handle with the maple tree.
Correct, this does not use the Maple tree yet but once Maple tree
transition happens and it supports RCU-safe lookups, my code in
find_vma_under_rcu() becomes really simple.
>
> On Thu 01-09-22 10:34:48, Suren Baghdasaryan wrote:
> [...]
> > One notable way the implementation deviates from the proposal is the way
> > VMAs are marked as locked. Because during some of mm updates multiple
> > VMAs need to be locked until the end of the update (e.g. vma_merge,
> > split_vma, etc).
>
> I think it would be really helpful to spell out those issues in a greater
> detail. Not everybody is aware of those vma related subtleties.
Ack. I'll expand the description of the cases when multiple VMAs need
to be locked in the same update. The main difficulties are:
1. Multiple VMAs might need to be locked within one
mmap_write_lock/mmap_write_unlock session (will call it an update
transaction).
2. Figuring out when it's safe to unlock a previously locked VMA is
tricky because that might be happening in different functions and at
different call levels.
So, instead of the usual lock/unlock pattern, the proposed solution
marks a VMA as locked and provides an efficient way to:
1. Identify locked VMAs.
2. Unlock all locked VMAs in bulk.
We also postpone unlocking the locked VMAs until the end of the update
transaction, when we do mmap_write_unlock. Potentially this keeps a
VMA locked for longer than is absolutely necessary but it results in a
big reduction of code complexity.
>
> Thanks for working on this Suren!
Thanks for reviewing!
Suren.
> --
> Michal Hocko
> SUSE Labs
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>
next prev parent reply other threads:[~2022-09-05 18:33 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-01 17:34 [RFC PATCH RESEND 00/28] per-VMA locks proposal Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 01/28] mm: introduce CONFIG_PER_VMA_LOCK Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 02/28] mm: rcu safe VMA freeing Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 03/28] mm: introduce __find_vma to be used without mmap_lock protection Suren Baghdasaryan
2022-09-01 20:22 ` Kent Overstreet
2022-09-01 23:18 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 04/28] mm: move mmap_lock assert function definitions Suren Baghdasaryan
2022-09-01 20:24 ` Kent Overstreet
2022-09-01 20:51 ` Liam Howlett
2022-09-01 23:21 ` Suren Baghdasaryan
2022-09-02 6:23 ` Sebastian Andrzej Siewior
2022-09-02 17:46 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 05/28] mm: add per-VMA lock and helper functions to control it Suren Baghdasaryan
2022-09-06 13:46 ` Laurent Dufour
2022-09-06 17:24 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 06/28] mm: mark VMA as locked whenever vma->vm_flags are modified Suren Baghdasaryan
2022-09-06 14:26 ` Laurent Dufour
2022-09-06 19:00 ` Suren Baghdasaryan
2022-09-06 20:00 ` Liam Howlett
2022-09-06 20:13 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 07/28] kernel/fork: mark VMAs as locked before copying pages during fork Suren Baghdasaryan
2022-09-06 14:37 ` Laurent Dufour
2022-09-08 23:57 ` Suren Baghdasaryan
2022-09-09 13:27 ` Laurent Dufour
2022-09-09 16:29 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 08/28] mm/khugepaged: mark VMA as locked while collapsing a hugepage Suren Baghdasaryan
2022-09-06 14:43 ` Laurent Dufour
2022-09-09 0:15 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 09/28] mm/mempolicy: mark VMA as locked when changing protection policy Suren Baghdasaryan
2022-09-06 14:47 ` Laurent Dufour
2022-09-09 0:27 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 10/28] mm/mmap: mark VMAs as locked in vma_adjust Suren Baghdasaryan
2022-09-06 15:35 ` Laurent Dufour
2022-09-09 0:51 ` Suren Baghdasaryan
2022-09-09 15:52 ` Laurent Dufour
2022-09-01 17:34 ` [RFC PATCH RESEND 11/28] mm/mmap: mark VMAs as locked before merging or splitting them Suren Baghdasaryan
2022-09-06 15:44 ` Laurent Dufour
2022-09-01 17:35 ` [RFC PATCH RESEND 12/28] mm/mremap: mark VMA as locked while remapping it to a new address range Suren Baghdasaryan
2022-09-06 16:09 ` Laurent Dufour
2022-09-01 17:35 ` [RFC PATCH RESEND 13/28] mm: conditionally mark VMA as locked in free_pgtables and unmap_page_range Suren Baghdasaryan
2022-09-09 10:33 ` Laurent Dufour
2022-09-09 16:43 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 14/28] mm: mark VMAs as locked before isolating them Suren Baghdasaryan
2022-09-09 13:35 ` Laurent Dufour
2022-09-09 16:28 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 15/28] mm/mmap: mark adjacent VMAs as locked if they can grow into unmapped area Suren Baghdasaryan
2022-09-09 13:43 ` Laurent Dufour
2022-09-09 16:25 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 16/28] kernel/fork: assert no VMA readers during its destruction Suren Baghdasaryan
2022-09-09 13:56 ` Laurent Dufour
2022-09-09 16:19 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 17/28] mm/mmap: prevent pagefault handler from racing with mmu_notifier registration Suren Baghdasaryan
2022-09-09 14:20 ` Laurent Dufour
2022-09-09 16:12 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 18/28] mm: add FAULT_FLAG_VMA_LOCK flag Suren Baghdasaryan
2022-09-09 14:26 ` Laurent Dufour
2022-09-01 17:35 ` [RFC PATCH RESEND 19/28] mm: disallow do_swap_page to handle page faults under VMA lock Suren Baghdasaryan
2022-09-06 19:39 ` Peter Xu
2022-09-06 20:08 ` Suren Baghdasaryan
2022-09-06 20:22 ` Peter Xu
2022-09-07 0:58 ` Suren Baghdasaryan
2022-09-09 14:26 ` Laurent Dufour
2022-09-01 17:35 ` [RFC PATCH RESEND 20/28] mm: introduce per-VMA lock statistics Suren Baghdasaryan
2022-09-09 14:28 ` Laurent Dufour
2022-09-09 16:11 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 21/28] mm: introduce find_and_lock_anon_vma to be used from arch-specific code Suren Baghdasaryan
2022-09-09 14:38 ` Laurent Dufour
2022-09-09 16:10 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 22/28] x86/mm: try VMA lock-based page fault handling first Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 23/28] x86/mm: define ARCH_SUPPORTS_PER_VMA_LOCK Suren Baghdasaryan
2022-09-01 20:20 ` Kent Overstreet
2022-09-01 23:17 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 24/28] arm64/mm: try VMA lock-based page fault handling first Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 25/28] arm64/mm: define ARCH_SUPPORTS_PER_VMA_LOCK Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 26/28] powerc/mm: try VMA lock-based page fault handling first Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 27/28] powerpc/mm: define ARCH_SUPPORTS_PER_VMA_LOCK Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 28/28] kernel/fork: throttle call_rcu() calls in vm_area_free Suren Baghdasaryan
2022-09-09 15:19 ` Laurent Dufour
2022-09-09 16:02 ` Suren Baghdasaryan
2022-09-09 16:14 ` Laurent Dufour
2022-09-01 20:58 ` [RFC PATCH RESEND 00/28] per-VMA locks proposal Kent Overstreet
2022-09-01 23:26 ` Suren Baghdasaryan
2022-09-11 9:35 ` Vlastimil Babka
2022-09-28 2:28 ` Suren Baghdasaryan
2022-09-29 11:18 ` Vlastimil Babka
2022-09-02 7:42 ` Peter Zijlstra
2022-09-02 14:45 ` Suren Baghdasaryan
2022-09-05 12:32 ` Michal Hocko
2022-09-05 18:32 ` Suren Baghdasaryan [this message]
2022-09-05 20:35 ` Kent Overstreet
2022-09-06 15:46 ` Suren Baghdasaryan
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