From: Roman Gushchin <guro@fb.com>
To: Yang Shi <shy828301@gmail.com>
Cc: <ktkhai@virtuozzo.com>, <vbabka@suse.cz>, <shakeelb@google.com>,
<david@fromorbit.com>, <hannes@cmpxchg.org>, <mhocko@suse.com>,
<akpm@linux-foundation.org>, <linux-mm@kvack.org>,
<linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [v7 PATCH 07/12] mm: vmscan: use a new flag to indicate shrinker is registered
Date: Tue, 9 Feb 2021 16:39:43 -0800 [thread overview]
Message-ID: <20210210003943.GK524633@carbon.DHCP.thefacebook.com> (raw)
In-Reply-To: <20210209174646.1310591-8-shy828301@gmail.com>
On Tue, Feb 09, 2021 at 09:46:41AM -0800, Yang Shi wrote:
> Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred.
> This approach is fine with nr_deferred at the shrinker level, but the following
> patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their
> shrinker->nr_deferred would always be NULL. This would prevent the shrinkers
> from unregistering correctly.
>
> Remove SHRINKER_REGISTERING since we could check if shrinker is registered
> successfully by the new flag.
>
> Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
> include/linux/shrinker.h | 7 ++++---
> mm/vmscan.c | 31 +++++++++----------------------
> 2 files changed, 13 insertions(+), 25 deletions(-)
>
> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index 0f80123650e2..1eac79ce57d4 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -79,13 +79,14 @@ struct shrinker {
> #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
>
> /* Flags */
> -#define SHRINKER_NUMA_AWARE (1 << 0)
> -#define SHRINKER_MEMCG_AWARE (1 << 1)
> +#define SHRINKER_REGISTERED (1 << 0)
> +#define SHRINKER_NUMA_AWARE (1 << 1)
> +#define SHRINKER_MEMCG_AWARE (1 << 2)
> /*
> * It just makes sense when the shrinker is also MEMCG_AWARE for now,
> * non-MEMCG_AWARE shrinker should not have this flag set.
> */
> -#define SHRINKER_NONSLAB (1 << 2)
> +#define SHRINKER_NONSLAB (1 << 3)
>
> extern int prealloc_shrinker(struct shrinker *shrinker);
> extern void register_shrinker_prepared(struct shrinker *shrinker);
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 273efbf4d53c..a047980536cf 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
> }
> }
>
> -/*
> - * We allow subsystems to populate their shrinker-related
> - * LRU lists before register_shrinker_prepared() is called
> - * for the shrinker, since we don't want to impose
> - * restrictions on their internal registration order.
> - * In this case shrink_slab_memcg() may find corresponding
> - * bit is set in the shrinkers map.
> - *
> - * This value is used by the function to detect registering
> - * shrinkers and to skip do_shrink_slab() calls for them.
> - */
> -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
> -
> static DEFINE_IDR(shrinker_idr);
>
> static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
>
> down_write(&shrinker_rwsem);
> /* This may call shrinker, so it must use down_read_trylock() */
> - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
> + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
> if (id < 0)
> goto unlock;
>
> @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
> {
> down_write(&shrinker_rwsem);
> list_add_tail(&shrinker->list, &shrinker_list);
> -#ifdef CONFIG_MEMCG
> - if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> - idr_replace(&shrinker_idr, shrinker, shrinker->id);
> -#endif
> + shrinker->flags |= SHRINKER_REGISTERED;
> up_write(&shrinker_rwsem);
> }
>
> @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker);
> */
> void unregister_shrinker(struct shrinker *shrinker)
> {
> - if (!shrinker->nr_deferred)
> + if (!(shrinker->flags & SHRINKER_REGISTERED))
> return;
> - if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> - unregister_memcg_shrinker(shrinker);
> +
> down_write(&shrinker_rwsem);
> list_del(&shrinker->list);
> + shrinker->flags &= ~SHRINKER_REGISTERED;
> up_write(&shrinker_rwsem);
> +
> + if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> + unregister_memcg_shrinker(shrinker);
Because unregister_memcg_shrinker() will take and release shrinker_rwsem once again,
I wonder if it's better to move it into the locked section and change the calling
convention to require the caller to take the semaphore?
> kfree(shrinkrem->nr_deferred);
> shrinker->nr_deferred = NULL;
> }
> @@ -693,7 +680,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
> struct shrinker *shrinker;
>
> shrinker = idr_find(&shrinker_idr, i);
> - if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) {
> + if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) {
> if (!shrinker)
> clear_bit(i, info->map);
> continue;
> --
> 2.26.2
>
next prev parent reply other threads:[~2021-02-10 0:40 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210209174646.1310591-1-shy828301@gmail.com>
2021-02-09 17:46 ` [v7 PATCH 01/12] mm: vmscan: use nid from shrink_control for tracepoint Yang Shi
2021-02-09 19:14 ` Shakeel Butt
2021-02-10 16:58 ` Yang Shi
2021-02-09 19:21 ` Roman Gushchin
2021-02-09 17:46 ` [v7 PATCH 02/12] mm: vmscan: consolidate shrinker_maps handling code Yang Shi
2021-02-09 20:27 ` Roman Gushchin
2021-02-10 14:19 ` Shakeel Butt
2021-02-09 17:46 ` [v7 PATCH 03/12] mm: vmscan: use shrinker_rwsem to protect shrinker_maps allocation Yang Shi
2021-02-09 20:33 ` Roman Gushchin
2021-02-09 23:28 ` Yang Shi
2021-02-09 17:46 ` [v7 PATCH 04/12] mm: vmscan: remove memcg_shrinker_map_size Yang Shi
2021-02-09 20:43 ` Roman Gushchin
2021-02-09 23:31 ` Yang Shi
2021-02-10 18:14 ` Vlastimil Babka
2021-02-09 17:46 ` [v7 PATCH 05/12] mm: memcontrol: rename shrinker_map to shrinker_info Yang Shi
2021-02-09 20:50 ` Roman Gushchin
2021-02-09 23:33 ` Yang Shi
2021-02-10 0:16 ` Roman Gushchin
2021-02-11 16:47 ` Kirill Tkhai
2021-02-11 17:29 ` Yang Shi
2021-02-09 17:46 ` [v7 PATCH 06/12] mm: vmscan: add shrinker_info_protected() helper Yang Shi
2021-02-10 0:22 ` Roman Gushchin
2021-02-10 1:07 ` Yang Shi
2021-02-10 1:29 ` Roman Gushchin
2021-02-10 12:12 ` Kirill Tkhai
2021-02-10 18:17 ` Vlastimil Babka
2021-02-12 6:54 ` [mm] bd741fb2ad: WARNING:suspicious_RCU_usage kernel test robot
2021-02-09 17:46 ` [v7 PATCH 07/12] mm: vmscan: use a new flag to indicate shrinker is registered Yang Shi
2021-02-10 0:39 ` Roman Gushchin [this message]
2021-02-10 1:12 ` Yang Shi
2021-02-10 1:34 ` Roman Gushchin
2021-02-10 1:55 ` Yang Shi
2021-02-10 18:45 ` Yang Shi
2021-02-10 18:23 ` Vlastimil Babka
2021-02-09 17:46 ` [v7 PATCH 08/12] mm: vmscan: add per memcg shrinker nr_deferred Yang Shi
2021-02-10 1:10 ` Roman Gushchin
2021-02-10 1:25 ` Yang Shi
2021-02-10 1:40 ` Roman Gushchin
2021-02-10 1:57 ` Yang Shi
2021-02-09 17:46 ` [v7 PATCH 09/12] mm: vmscan: use per memcg nr_deferred of shrinker Yang Shi
2021-02-10 1:27 ` Roman Gushchin
2021-02-10 1:52 ` Yang Shi
2021-02-10 14:36 ` Kirill Tkhai
2021-02-10 16:41 ` Yang Shi
2021-02-09 17:46 ` [v7 PATCH 10/12] mm: vmscan: don't need allocate shrinker->nr_deferred for memcg aware shrinkers Yang Shi
2021-02-10 1:23 ` Roman Gushchin
2021-02-09 17:46 ` [v7 PATCH 11/12] mm: memcontrol: reparent nr_deferred when memcg offline Yang Shi
2021-02-10 1:18 ` Roman Gushchin
2021-02-09 17:46 ` [v7 PATCH 12/12] mm: vmscan: shrink deferred objects proportional to priority Yang Shi
2021-02-11 13:10 ` Vlastimil Babka
2021-02-11 17:29 ` Yang Shi
2021-02-11 18:52 ` Vlastimil Babka
2021-02-11 19:15 ` Yang Shi
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