From: Peter Zijlstra <peterz@infradead.org>
To: "Liam R. Howlett" <Liam.Howlett@oracle.com>,
Suren Baghdasaryan <surenb@google.com>,
akpm@linux-foundation.org, willy@infradead.org,
lorenzo.stoakes@oracle.com, mhocko@suse.com, vbabka@suse.cz,
hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com,
mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com,
oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org,
brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com,
hughd@google.com, lokeshgidra@google.com, minchan@google.com,
jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com,
pasha.tatashin@soleen.com, klarasmodin@gmail.com, corbet@lwn.net,
linux-doc@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH v6 10/16] mm: replace vm_lock and detached flag with a reference count
Date: Thu, 19 Dec 2024 19:46:42 +0100 [thread overview]
Message-ID: <20241219184642.GF26279@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <rnanfpzs6fmojyeaowt65mug6xekorrkeefvn3b4zc7buunzhc@rrzcbhkrjdv4>
On Thu, Dec 19, 2024 at 01:18:23PM -0500, Liam R. Howlett wrote:
> > For RCU lookups only the mas tree matters -- and its left present there.
> >
> > If you really want to block RCU readers, I would suggest punching a hole
> > in the mm_mt. All the traditional code won't notice anyway, this is all
> > with mmap_lock held for writing.
>
> We don't want to block all rcu readers, we want to block the rcu readers
> that would see the problem - that is, anyone trying to read a particular
> area.
>
> Right now we can page fault in unpopulated vmas while writing other vmas
> to the tree. We are also moving more users to rcu reading to use the
> vmas they need without waiting on writes to finish.
>
> Maybe I don't understand your suggestion, but I would think punching a
> hole would lose this advantage?
My suggestion was to remove the range stuck in mas_detach from mm_mt.
That is exactly the affected range, no?
next prev parent reply other threads:[~2024-12-19 18:47 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-16 19:24 [PATCH v6 00/16] move per-vma lock into vm_area_struct Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 01/16] mm: introduce vma_start_read_locked{_nested} helpers Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 02/16] mm: move per-vma lock into vm_area_struct Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 03/16] mm: mark vma as detached until it's added into vma tree Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 04/16] mm/nommu: fix the last places where vma is not locked before being attached Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 05/16] types: move struct rcuwait into types.h Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 06/16] mm: allow vma_start_read_locked/vma_start_read_locked_nested to fail Suren Baghdasaryan
2024-12-17 11:31 ` Lokesh Gidra
2024-12-17 15:51 ` Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 07/16] mm: move mmap_init_lock() out of the header file Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 08/16] mm: uninline the main body of vma_start_write() Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 09/16] refcount: introduce __refcount_{add|inc}_not_zero_limited Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 10/16] mm: replace vm_lock and detached flag with a reference count Suren Baghdasaryan
2024-12-16 20:42 ` Peter Zijlstra
2024-12-16 20:53 ` Suren Baghdasaryan
2024-12-16 21:15 ` Peter Zijlstra
2024-12-16 21:53 ` Suren Baghdasaryan
2024-12-16 22:00 ` Peter Zijlstra
2024-12-16 21:37 ` Peter Zijlstra
2024-12-16 21:44 ` Suren Baghdasaryan
2024-12-17 10:30 ` Peter Zijlstra
2024-12-17 16:27 ` Suren Baghdasaryan
2024-12-18 9:41 ` Peter Zijlstra
2024-12-18 10:06 ` Peter Zijlstra
2024-12-18 15:37 ` Liam R. Howlett
2024-12-18 15:50 ` Suren Baghdasaryan
2024-12-18 16:18 ` Peter Zijlstra
2024-12-18 17:36 ` Suren Baghdasaryan
2024-12-18 17:44 ` Peter Zijlstra
2024-12-18 17:58 ` Suren Baghdasaryan
2024-12-18 19:00 ` Liam R. Howlett
2024-12-18 19:07 ` Suren Baghdasaryan
2024-12-18 19:29 ` Suren Baghdasaryan
2024-12-18 19:38 ` Liam R. Howlett
2024-12-18 20:00 ` Suren Baghdasaryan
2024-12-18 20:38 ` Liam R. Howlett
2024-12-18 21:53 ` Suren Baghdasaryan
2024-12-18 21:55 ` Suren Baghdasaryan
2024-12-19 0:35 ` Andrew Morton
2024-12-19 0:47 ` Suren Baghdasaryan
2024-12-19 9:13 ` Peter Zijlstra
2024-12-19 11:20 ` Peter Zijlstra
2024-12-19 16:17 ` Suren Baghdasaryan
2024-12-19 17:16 ` Liam R. Howlett
2024-12-19 17:42 ` Peter Zijlstra
2024-12-19 18:18 ` Liam R. Howlett
2024-12-19 18:46 ` Peter Zijlstra [this message]
2024-12-19 18:55 ` Liam R. Howlett
2024-12-20 15:22 ` Suren Baghdasaryan
2024-12-23 3:03 ` Suren Baghdasaryan
2024-12-26 17:12 ` Suren Baghdasaryan
2024-12-19 16:14 ` Suren Baghdasaryan
2024-12-19 17:23 ` Peter Zijlstra
2024-12-19 8:55 ` Peter Zijlstra
2024-12-19 16:08 ` Suren Baghdasaryan
2024-12-19 8:53 ` Peter Zijlstra
2024-12-19 16:08 ` Suren Baghdasaryan
2024-12-18 15:57 ` Suren Baghdasaryan
2024-12-18 16:13 ` Peter Zijlstra
2024-12-18 15:42 ` Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 11/16] mm: enforce vma to be in detached state before freeing Suren Baghdasaryan
2024-12-16 21:16 ` Peter Zijlstra
2024-12-16 21:18 ` Peter Zijlstra
2024-12-16 21:57 ` Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 12/16] mm: remove extra vma_numab_state_init() call Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 13/16] mm: introduce vma_ensure_detached() Suren Baghdasaryan
2024-12-17 10:26 ` Peter Zijlstra
2024-12-17 15:58 ` Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 14/16] mm: prepare lock_vma_under_rcu() for vma reuse possibility Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 15/16] mm: make vma cache SLAB_TYPESAFE_BY_RCU Suren Baghdasaryan
2024-12-16 19:24 ` [PATCH v6 16/16] docs/mm: document latest changes to vm_lock Suren Baghdasaryan
2024-12-16 19:39 ` [PATCH v6 00/16] move per-vma lock into vm_area_struct Suren Baghdasaryan
2024-12-17 18:42 ` Andrew Morton
2024-12-17 18:49 ` Suren Baghdasaryan
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