From: Dave Chinner <david@fromorbit.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>,
akpm@linux-foundation.org, paulmck@kernel.org, tkhai@ya.ru,
vbabka@suse.cz, roman.gushchin@linux.dev, djwong@kernel.org,
brauner@kernel.org, tytso@mit.edu, steven.price@arm.com,
cel@kernel.org, senozhatsky@chromium.org, yujie.liu@intel.com,
gregkh@linuxfoundation.org, muchun.song@linux.dev,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v6 42/45] mm: shrinker: make global slab shrink lockless
Date: Wed, 6 Dec 2023 20:13:21 +1100 [thread overview]
Message-ID: <ZXA7MS+p/YjrN4Lj@dread.disaster.area> (raw)
In-Reply-To: <CAJhGHyBJiYOQGY3t=Lpe4A-rmJML8Mn8GC35GkrQ6Us082ZTAQ@mail.gmail.com>
On Wed, Dec 06, 2023 at 04:23:24PM +0800, Lai Jiangshan wrote:
> On Wed, Dec 6, 2023 at 3:55 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> > On 2023/12/6 15:47, Lai Jiangshan wrote:
> > > On Tue, Sep 12, 2023 at 9:57 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> > >
> > No, this_shrinker will not be removed from the shrinker_list until the
> > last refcount is released. See below:
> >
> > > rcu_read_lock();
> > > shrinker_put(this_shrinker);
> >
> > CPU 1 CPU 2
> >
> > --> if (refcount_dec_and_test(&shrinker->refcount))
> > complete(&shrinker->done);
> >
> > wait_for_completion(&shrinker->done);
> > list_del_rcu(&shrinker->list);
>
> since shrinker will not be removed from the shrinker_list until the
> last refcount is released.
>
> Is it possible that shrinker_free() can be starved by continuous
> scanners getting and putting the refcount?
In theory, yes. In practice, highly improbable. i.e. I don't think
this will ever be an issue because the timing conditions for memory
reclaim to keep a permanently elevated reference count on a shrinker
for a subsystem that is being torn down are -highly- improbable.
And even if you could pull it off, who cares if shrinker_free() is
delayed? It's a teardown operation meaning the subsystem using the
shrinker will no longer be in use so the latency of the teardown
operation is largely irrelevant to whatever is still running
on the system.
-Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2023-12-06 9:13 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-11 9:43 [PATCH v6 00/45] use refcount+RCU method to implement lockless slab shrink Qi Zheng
2023-09-11 9:44 ` [PATCH v6 01/45] mm: shrinker: add infrastructure for dynamically allocating shrinker Qi Zheng
2023-09-18 9:03 ` Muchun Song
2023-09-18 12:06 ` Qi Zheng
2023-09-19 2:36 ` Muchun Song
2023-09-19 2:46 ` [PATCH] mm: shrinker: some cleanup Qi Zheng
2023-09-19 8:04 ` Greg KH
2023-09-19 8:41 ` Qi Zheng
2023-09-11 9:44 ` [PATCH v6 02/45] kvm: mmu: dynamically allocate the x86-mmu shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 03/45] binder: dynamically allocate the android-binder shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 04/45] drm/ttm: dynamically allocate the drm-ttm_pool shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 05/45] xenbus/backend: dynamically allocate the xen-backend shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 06/45] erofs: dynamically allocate the erofs-shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 07/45] f2fs: dynamically allocate the f2fs-shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 08/45] gfs2: dynamically allocate the gfs2-glock shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 09/45] gfs2: dynamically allocate the gfs2-qd shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 10/45] NFSv4.2: dynamically allocate the nfs-xattr shrinkers Qi Zheng
2023-09-11 9:44 ` [PATCH v6 11/45] nfs: dynamically allocate the nfs-acl shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 12/45] nfsd: dynamically allocate the nfsd-filecache shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 13/45] quota: dynamically allocate the dquota-cache shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 14/45] ubifs: dynamically allocate the ubifs-slab shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 15/45] rcu: dynamically allocate the rcu-lazy shrinker Qi Zheng
2023-09-18 7:27 ` Muchun Song
2023-09-11 9:44 ` [PATCH v6 16/45] rcu: dynamically allocate the rcu-kfree shrinker Qi Zheng
2023-09-12 7:30 ` Uladzislau Rezki
2023-09-11 9:44 ` [PATCH v6 17/45] mm: thp: dynamically allocate the thp-related shrinkers Qi Zheng
2023-09-11 9:44 ` [PATCH v6 18/45] sunrpc: dynamically allocate the sunrpc_cred shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 19/45] mm: workingset: dynamically allocate the mm-shadow shrinker Qi Zheng
2023-09-18 7:26 ` Muchun Song
2023-09-11 9:44 ` [PATCH v6 20/45] drm/i915: dynamically allocate the i915_gem_mm shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 21/45] drm/msm: dynamically allocate the drm-msm_gem shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 22/45] drm/panfrost: dynamically allocate the drm-panfrost shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 23/45] dm: dynamically allocate the dm-bufio shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 24/45] dm zoned: dynamically allocate the dm-zoned-meta shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 25/45] md/raid5: dynamically allocate the md-raid5 shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 26/45] bcache: dynamically allocate the md-bcache shrinker Qi Zheng
2023-09-18 7:24 ` Muchun Song
2023-09-11 9:44 ` [PATCH v6 27/45] vmw_balloon: dynamically allocate the vmw-balloon shrinker Qi Zheng
2023-09-11 18:40 ` Nadav Amit
2023-09-11 9:44 ` [PATCH v6 28/45] virtio_balloon: dynamically allocate the virtio-balloon shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 29/45] mbcache: dynamically allocate the mbcache shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 30/45] ext4: dynamically allocate the ext4-es shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 31/45] jbd2,ext4: dynamically allocate the jbd2-journal shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 32/45] nfsd: dynamically allocate the nfsd-client shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 33/45] nfsd: dynamically allocate the nfsd-reply shrinker Qi Zheng
2023-09-18 7:21 ` Muchun Song
2023-09-11 9:44 ` [PATCH v6 34/45] xfs: dynamically allocate the xfs-buf shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 35/45] xfs: dynamically allocate the xfs-inodegc shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 36/45] xfs: dynamically allocate the xfs-qm shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 37/45] zsmalloc: dynamically allocate the mm-zspool shrinker Qi Zheng
2023-09-11 9:44 ` [PATCH v6 38/45] fs: super: dynamically allocate the s_shrink Qi Zheng
2023-09-13 17:03 ` David Sterba
2023-09-11 9:44 ` [PATCH v6 39/45] mm: shrinker: remove old APIs Qi Zheng
2023-09-11 9:44 ` [PATCH v6 40/45] mm: shrinker: add a secondary array for shrinker_info::{map, nr_deferred} Qi Zheng
2023-09-28 14:15 ` [PATCH] fixup: " Qi Zheng
2023-09-28 14:17 ` Qi Zheng
2023-09-11 9:44 ` [PATCH v6 41/45] mm: shrinker: rename {prealloc|unregister}_memcg_shrinker() to shrinker_memcg_{alloc|remove}() Qi Zheng
2023-09-18 7:20 ` Muchun Song
2023-09-11 9:44 ` [PATCH v6 42/45] mm: shrinker: make global slab shrink lockless Qi Zheng
2023-12-06 7:47 ` Lai Jiangshan
2023-12-06 7:55 ` Qi Zheng
2023-12-06 8:10 ` Lai Jiangshan
2023-12-06 8:23 ` Lai Jiangshan
2023-12-06 8:37 ` Qi Zheng
2023-12-06 9:13 ` Dave Chinner [this message]
2023-09-11 9:44 ` [PATCH v6 43/45] mm: shrinker: make memcg " Qi Zheng
2023-09-11 9:44 ` [PATCH v6 44/45] mm: shrinker: hold write lock to reparent shrinker nr_deferred Qi Zheng
2023-09-18 7:17 ` Muchun Song
2023-09-11 9:44 ` [PATCH v6 45/45] mm: shrinker: convert shrinker_rwsem to mutex Qi Zheng
2023-09-18 7:16 ` Muchun Song
2023-11-26 14:27 ` [PATCH v6 00/45] use refcount+RCU method to implement lockless slab shrink Ryan Lahfa
2023-11-27 13:53 ` Greg KH
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