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From: Andrew Morton <akpm@linux-foundation.org>
To: Suren Baghdasaryan <surenb@google.com>
Cc: michel@lespinasse.org, jglisse@google.com, mhocko@suse.com,
	vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net,
	dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com,
	peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org,
	mingo@redhat.com, will@kernel.org, luto@kernel.org,
	songliubraving@fb.com, peterx@redhat.com, david@redhat.com,
	dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de,
	kent.overstreet@linux.dev, punit.agrawal@bytedance.com,
	lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com,
	axelrasmussen@google.com, joelaf@google.com, minchan@google.com,
	rppt@kernel.org, jannh@google.com, shakeelb@google.com,
	tatashin@google.com, edumazet@google.com, gthelen@google.com,
	gurua@google.com, arjunroy@google.com, soheil@google.com,
	leewalsh@google.com, posk@google.com, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org,
	linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
	linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH v2 00/33] Per-VMA locks
Date: Fri, 27 Jan 2023 14:51:38 -0800	[thread overview]
Message-ID: <20230127145138.8cc44bf00ebf289dffec0975@linux-foundation.org> (raw)
In-Reply-To: <20230127194110.533103-1-surenb@google.com>

On Fri, 27 Jan 2023 11:40:37 -0800 Suren Baghdasaryan <surenb@google.com> wrote:

> Per-vma locks idea that was discussed during SPF [1] discussion at LSF/MM
> last year [2], which concluded with suggestion that “a reader/writer
> semaphore could be put into the VMA itself; that would have the effect of
> using the VMA as a sort of range lock. There would still be contention at
> the VMA level, but it would be an improvement.” This patchset implements
> this suggested approach.

I think I'll await reviewer/tester input for a while.

> The patchset implements per-VMA locking only for anonymous pages which
> are not in swap and avoids userfaultfs as their implementation is more
> complex. Additional support for file-back page faults, swapped and user
> pages can be added incrementally.

This is a significant risk.  How can we be confident that these as yet
unimplemented parts are implementable and that the result will be good?


  parent reply	other threads:[~2023-01-27 22:51 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-27 19:40 [PATCH v2 00/33] Per-VMA locks Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 01/33] maple_tree: Be more cautious about dead nodes Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 02/33] maple_tree: Detect dead nodes in mas_start() Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 03/33] maple_tree: Fix freeing of nodes in rcu mode Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 04/33] maple_tree: remove extra smp_wmb() from mas_dead_leaves() Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 05/33] maple_tree: Fix write memory barrier of nodes once dead for RCU mode Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 06/33] maple_tree: Add smp_rmb() to dead node detection Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 07/33] mm: Enable maple tree RCU mode by default Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 08/33] mm: introduce CONFIG_PER_VMA_LOCK Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 09/33] mm: rcu safe VMA freeing Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 10/33] mm: move mmap_lock assert function definitions Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 11/33] mm: add per-VMA lock and helper functions to control it Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 12/33] mm: mark VMA as being written when changing vm_flags Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 13/33] mm/mmap: move VMA locking before vma_adjust_trans_huge call Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 14/33] mm/khugepaged: write-lock VMA while collapsing a huge page Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 15/33] mm/mmap: write-lock VMAs before merging, splitting or expanding them Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 16/33] mm/mmap: write-lock VMA before shrinking or expanding it Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 17/33] mm/mremap: write-lock VMA while remapping it to a new address range Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 18/33] mm: write-lock VMAs before removing them from VMA tree Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 19/33] mm: conditionally write-lock VMA in free_pgtables Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 20/33] mm/mmap: write-lock adjacent VMAs if they can grow into unmapped area Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 21/33] kernel/fork: assert no VMA readers during its destruction Suren Baghdasaryan
2023-01-27 19:40 ` [PATCH v2 22/33] mm/mmap: prevent pagefault handler from racing with mmu_notifier registration Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 23/33] mm: introduce lock_vma_under_rcu to be used from arch-specific code Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 24/33] mm: fall back to mmap_lock if vma->anon_vma is not yet set Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 25/33] mm: add FAULT_FLAG_VMA_LOCK flag Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 26/33] mm: prevent do_swap_page from handling page faults under VMA lock Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 27/33] mm: prevent userfaults to be handled under per-vma lock Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 28/33] mm: introduce per-VMA lock statistics Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 29/33] x86/mm: try VMA lock-based page fault handling first Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 30/33] arm64/mm: " Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 31/33] powerc/mm: " Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 32/33] mm/mmap: free vm_area_struct without call_rcu in exit_mmap Suren Baghdasaryan
2023-01-27 19:41 ` [PATCH v2 33/33] mm: separate vma->lock from vm_area_struct Suren Baghdasaryan
2023-01-27 22:51 ` Andrew Morton [this message]
2023-01-27 23:26   ` [PATCH v2 00/33] Per-VMA locks Matthew Wilcox
2023-01-28  0:00     ` Suren Baghdasaryan
2023-02-14 16:47       ` Suren Baghdasaryan
2023-02-15 17:32 ` [External] " Punit Agrawal
2023-02-15 17:39   ` Suren Baghdasaryan
2023-02-28 12:06   ` Punit Agrawal
2023-02-28 18:08     ` Suren Baghdasaryan

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