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Date: Tue, 20 Feb 2024 09:42:53 +0800
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Subject: Re: [PATCH 1/2] mm/rmap: support folio_referenced to control if
 try_lock in rmap_walk
To: akpm@linux-foundation.org, david@redhat.com, osalvador@suse.de,
 willy@infradead.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, tkjos@google.com,
 surenb@google.com, gregkh@google.com, v-songbaohua@oppo.com
References: <20240219141703.3851-1-lipeifeng@oppo.com>
 <20240219141703.3851-2-lipeifeng@oppo.com>
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在 2024/2/19 22:17, lipeifeng@oppo.com 写道:
> From: lipeifeng <lipeifeng@oppo.com>
>
> The patch to support folio_referenced to control the bevavior
> of walk_rmap, which for some thread to hold the lock in rmap_walk
> instead of try_lock when using folio_referenced.
>
> Signed-off-by: lipeifeng <lipeifeng@oppo.com>
> ---
>   include/linux/rmap.h |  5 +++--
>   mm/rmap.c            |  5 +++--
>   mm/vmscan.c          | 16 ++++++++++++++--
>   3 files changed, 20 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> index b7944a8..846b261 100644
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -623,7 +623,8 @@ static inline int folio_try_share_anon_rmap_pmd(struct folio *folio,
>    * Called from mm/vmscan.c to handle paging out
>    */
>   int folio_referenced(struct folio *, int is_locked,
> -			struct mem_cgroup *memcg, unsigned long *vm_flags);
> +			struct mem_cgroup *memcg, unsigned long *vm_flags,
> +			unsigned int rw_try_lock);
>   
>   void try_to_migrate(struct folio *folio, enum ttu_flags flags);
>   void try_to_unmap(struct folio *, enum ttu_flags flags);
> @@ -739,7 +740,7 @@ struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
>   
>   static inline int folio_referenced(struct folio *folio, int is_locked,
>   				  struct mem_cgroup *memcg,
> -				  unsigned long *vm_flags)
> +				  unsigned long *vm_flags, unsigned int rw_try_lock)
>   {
>   	*vm_flags = 0;
>   	return 0;
> diff --git a/mm/rmap.c b/mm/rmap.c
> index f5d43ed..15d1fba 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -952,6 +952,7 @@ static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
>    * @is_locked: Caller holds lock on the folio.
>    * @memcg: target memory cgroup
>    * @vm_flags: A combination of all the vma->vm_flags which referenced the folio.
> + * @rw_try_lock: if try_lock in rmap_walk
>    *
>    * Quick test_and_clear_referenced for all mappings of a folio,
>    *
> @@ -959,7 +960,7 @@ static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
>    * the function bailed out due to rmap lock contention.
>    */
>   int folio_referenced(struct folio *folio, int is_locked,
> -		     struct mem_cgroup *memcg, unsigned long *vm_flags)
> +		     struct mem_cgroup *memcg, unsigned long *vm_flags, unsigned int rw_try_lock)
>   {
>   	int we_locked = 0;
>   	struct folio_referenced_arg pra = {
> @@ -970,7 +971,7 @@ int folio_referenced(struct folio *folio, int is_locked,
>   		.rmap_one = folio_referenced_one,
>   		.arg = (void *)&pra,
>   		.anon_lock = folio_lock_anon_vma_read,
> -		.try_lock = true,
> +		.try_lock = rw_try_lock ? true : false,
>   		.invalid_vma = invalid_folio_referenced_vma,
>   	};
>   
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 4f9c854..0296d48 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -136,6 +136,9 @@ struct scan_control {
>   	/* Always discard instead of demoting to lower tier memory */
>   	unsigned int no_demotion:1;
>   
> +	/* if try_lock in rmap_walk */
> +	unsigned int rw_try_lock:1;
> +
>   	/* Allocation order */
>   	s8 order;
>   
> @@ -827,7 +830,7 @@ static enum folio_references folio_check_references(struct folio *folio,
>   	unsigned long vm_flags;
>   
>   	referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
> -					   &vm_flags);
> +					   &vm_flags, sc->rw_try_lock);
>   	referenced_folio = folio_test_clear_referenced(folio);
>   
>   	/*
> @@ -1501,6 +1504,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
>   	struct scan_control sc = {
>   		.gfp_mask = GFP_KERNEL,
>   		.may_unmap = 1,
> +		.rw_try_lock = 1,
>   	};
>   	struct reclaim_stat stat;
>   	unsigned int nr_reclaimed;
> @@ -2038,7 +2042,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
>   
>   		/* Referenced or rmap lock contention: rotate */
>   		if (folio_referenced(folio, 0, sc->target_mem_cgroup,
> -				     &vm_flags) != 0) {
> +				     &vm_flags, sc->rw_try_lock) != 0) {
>   			/*
>   			 * Identify referenced, file-backed active folios and
>   			 * give them one more trip around the active list. So
> @@ -2096,6 +2100,7 @@ static unsigned int reclaim_folio_list(struct list_head *folio_list,
>   		.may_unmap = 1,
>   		.may_swap = 1,
>   		.no_demotion = 1,
> +		.rw_try_lock = 1,
>   	};
>   
>   	nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, false);
> @@ -5442,6 +5447,7 @@ static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
>   		.may_swap = true,
>   		.reclaim_idx = MAX_NR_ZONES - 1,
>   		.gfp_mask = GFP_KERNEL,
> +		.rw_try_lock = 1,
>   	};
>   
>   	buf = kvmalloc(len + 1, GFP_KERNEL);
> @@ -6414,6 +6420,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
>   		.may_writepage = !laptop_mode,
>   		.may_unmap = 1,
>   		.may_swap = 1,
> +		.rw_try_lock = 1,
>   	};
>   
>   	/*
> @@ -6459,6 +6466,7 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
>   		.may_unmap = 1,
>   		.reclaim_idx = MAX_NR_ZONES - 1,
>   		.may_swap = !noswap,
> +		.rw_try_lock = 1,
>   	};
>   
>   	WARN_ON_ONCE(!current->reclaim_state);
> @@ -6503,6 +6511,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
>   		.may_unmap = 1,
>   		.may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
>   		.proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
> +		.rw_try_lock = 1,
>   	};
>   	/*
>   	 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
> @@ -6764,6 +6773,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
>   		.gfp_mask = GFP_KERNEL,
>   		.order = order,
>   		.may_unmap = 1,
> +		.rw_try_lock = 1,
>   	};
>   
>   	set_task_reclaim_state(current, &sc.reclaim_state);
> @@ -7223,6 +7233,7 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
>   		.may_unmap = 1,
>   		.may_swap = 1,
>   		.hibernation_mode = 1,
> +		.rw_try_lock = 1,
>   	};
>   	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
>   	unsigned long nr_reclaimed;
> @@ -7381,6 +7392,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
>   		.may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
>   		.may_swap = 1,
>   		.reclaim_idx = gfp_zone(gfp_mask),
> +		.rw_try_lock = 1,
>   	};
>   	unsigned long pflags;
>