Re: [PATCH 2/8] mm, truncate: Do not check mapping for every page being truncated

Jan Kara
2017-10-19T08:11:50Z

On Wed 18-10-17 08:59:46, Mel Gorman wrote:
> During truncation, the mapping has already been checked for shmem and dax
> so it's known that workingset_update_node is required. This patch avoids
> the checks on mapping for each page being truncated. In all other cases,
> a lookup helper is used to determine if workingset_update_node() needs
> to be called. The one danger is that the API is slightly harder to use as
> calling workingset_update_node directly without checking for dax or shmem
> mappings could lead to surprises. However, the API rarely needs to be used
> and hopefully the comment is enough to give people the hint.
>
> sparsetruncate (tiny)
> 4.14.0-rc4 4.14.0-rc4
> oneirq-v1r1 pickhelper-v1r1
> Min Time 141.00 ( 0.00%) 140.00 ( 0.71%)
> 1st-qrtle Time 142.00 ( 0.00%) 141.00 ( 0.70%)
> 2nd-qrtle Time 142.00 ( 0.00%) 142.00 ( 0.00%)
> 3rd-qrtle Time 143.00 ( 0.00%) 143.00 ( 0.00%)
> Max-90% Time 144.00 ( 0.00%) 144.00 ( 0.00%)
> Max-95% Time 147.00 ( 0.00%) 145.00 ( 1.36%)
> Max-99% Time 195.00 ( 0.00%) 191.00 ( 2.05%)
> Max Time 230.00 ( 0.00%) 205.00 ( 10.87%)
> Amean Time 144.37 ( 0.00%) 143.82 ( 0.38%)
> Stddev Time 10.44 ( 0.00%) 9.00 ( 13.74%)
> Coeff Time 7.23 ( 0.00%) 6.26 ( 13.41%)
> Best99%Amean Time 143.72 ( 0.00%) 143.34 ( 0.26%)
> Best95%Amean Time 142.37 ( 0.00%) 142.00 ( 0.26%)
> Best90%Amean Time 142.19 ( 0.00%) 141.85 ( 0.24%)
> Best75%Amean Time 141.92 ( 0.00%) 141.58 ( 0.24%)
> Best50%Amean Time 141.69 ( 0.00%) 141.31 ( 0.27%)
> Best25%Amean Time 141.38 ( 0.00%) 140.97 ( 0.29%)
>
> As you'd expect, the gain is marginal but it can be detected. The differences
> in bonnie are all within the noise which is not surprising given the impact
> on the microbenchmark.
>
> radix_tree_update_node_t is a callback for some radix operations that
> optionally passes in a private field. The only user of the callback is
> workingset_update_node and as it no longer requires a mapping, the private
> field is removed.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

The patch looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> fs/dax.c | 2 +-
> include/linux/radix-tree.h | 7 +++----
> include/linux/swap.h | 13 ++++++++++++-
> lib/idr.c | 2 +-
> lib/radix-tree.c | 30 +++++++++++++-----------------
> mm/filemap.c | 7 ++++---
> mm/shmem.c | 2 +-
> mm/truncate.c | 2 +-
> mm/workingset.c | 10 ++--------
> tools/testing/radix-tree/multiorder.c | 2 +-
> 10 files changed, 39 insertions(+), 38 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index f001d8c72a06..3318ae9046e6 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -565,7 +565,7 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
> ret = __radix_tree_lookup(page_tree, index, &node, &slot);
> WARN_ON_ONCE(ret != entry);
> __radix_tree_replace(page_tree, node, slot,
> - new_entry, NULL, NULL);
> + new_entry, NULL);
> entry = new_entry;
> }
>
> diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
> index 567ebb5eaab0..0ca448c1cb42 100644
> --- a/include/linux/radix-tree.h
> +++ b/include/linux/radix-tree.h
> @@ -301,18 +301,17 @@ void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index,
> void *radix_tree_lookup(const struct radix_tree_root *, unsigned long);
> void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *,
> unsigned long index);
> -typedef void (*radix_tree_update_node_t)(struct radix_tree_node *, void *);
> +typedef void (*radix_tree_update_node_t)(struct radix_tree_node *);
> void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,
> void __rcu **slot, void *entry,
> - radix_tree_update_node_t update_node, void *private);
> + radix_tree_update_node_t update_node);
> void radix_tree_iter_replace(struct radix_tree_root *,
> const struct radix_tree_iter *, void __rcu **slot, void *entry);
> void radix_tree_replace_slot(struct radix_tree_root *,
> void __rcu **slot, void *entry);
> void __radix_tree_delete_node(struct radix_tree_root *,
> struct radix_tree_node *,
> - radix_tree_update_node_t update_node,
> - void *private);
> + radix_tree_update_node_t update_node);
> void radix_tree_iter_delete(struct radix_tree_root *,
> struct radix_tree_iter *iter, void __rcu **slot);
> void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 8a807292037f..257c48a525c8 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -292,7 +292,18 @@ struct vma_swap_readahead {
> void *workingset_eviction(struct address_space *mapping, struct page *page);
> bool workingset_refault(void *shadow);
> void workingset_activation(struct page *page);
> -void workingset_update_node(struct radix_tree_node *node, void *private);
> +
> +/* Do not use directly, use workingset_lookup_update */
> +void workingset_update_node(struct radix_tree_node *node);
> +
> +/* Returns workingset_update_node() if the mapping has shadow entries. */
> +#define workingset_lookup_update(mapping) \
> +({ \
> + radix_tree_update_node_t __helper = workingset_update_node; \
> + if (dax_mapping(mapping) || shmem_mapping(mapping)) \
> + __helper = NULL; \
> + __helper; \
> +})
>
> /* linux/mm/page_alloc.c */
> extern unsigned long totalram_pages;
> diff --git a/lib/idr.c b/lib/idr.c
> index edd9b2be1651..2593ce513a18 100644
> --- a/lib/idr.c
> +++ b/lib/idr.c
> @@ -171,7 +171,7 @@ void *idr_replace_ext(struct idr *idr, void *ptr, unsigned long id)
> if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
> return ERR_PTR(-ENOENT);
>
> - __radix_tree_replace(&idr->idr_rt, node, slot, ptr, NULL, NULL);
> + __radix_tree_replace(&idr->idr_rt, node, slot, ptr, NULL);
>
> return entry;
> }
> diff --git a/lib/radix-tree.c b/lib/radix-tree.c
> index 8b1feca1230a..c8d55565fafa 100644
> --- a/lib/radix-tree.c
> +++ b/lib/radix-tree.c
> @@ -677,8 +677,7 @@ static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
> * @root radix tree root
> */
> static inline bool radix_tree_shrink(struct radix_tree_root *root,
> - radix_tree_update_node_t update_node,
> - void *private)
> + radix_tree_update_node_t update_node)
> {
> bool shrunk = false;
>
> @@ -739,7 +738,7 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root,
> if (!radix_tree_is_internal_node(child)) {
> node->slots[0] = (void __rcu *)RADIX_TREE_RETRY;
> if (update_node)
> - update_node(node, private);
> + update_node(node);
> }
>
> WARN_ON_ONCE(!list_empty(&node->private_list));
> @@ -752,7 +751,7 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root,
>
> static bool delete_node(struct radix_tree_root *root,
> struct radix_tree_node *node,
> - radix_tree_update_node_t update_node, void *private)
> + radix_tree_update_node_t update_node)
> {
> bool deleted = false;
>
> @@ -762,8 +761,8 @@ static bool delete_node(struct radix_tree_root *root,
> if (node->count) {
> if (node_to_entry(node) ==
> rcu_dereference_raw(root->rnode))
> - deleted |= radix_tree_shrink(root, update_node,
> - private);
> + deleted |= radix_tree_shrink(root,
> + update_node);
> return deleted;
> }
>
> @@ -1173,7 +1172,6 @@ static int calculate_count(struct radix_tree_root *root,
> * @slot: pointer to slot in @node
> * @item: new item to store in the slot.
> * @update_node: callback for changing leaf nodes
> - * @private: private data to pass to @update_node
> *
> * For use with __radix_tree_lookup(). Caller must hold tree write locked
> * across slot lookup and replacement.
> @@ -1181,7 +1179,7 @@ static int calculate_count(struct radix_tree_root *root,
> void __radix_tree_replace(struct radix_tree_root *root,
> struct radix_tree_node *node,
> void __rcu **slot, void *item,
> - radix_tree_update_node_t update_node, void *private)
> + radix_tree_update_node_t update_node)
> {
> void *old = rcu_dereference_raw(*slot);
> int exceptional = !!radix_tree_exceptional_entry(item) -
> @@ -1201,9 +1199,9 @@ void __radix_tree_replace(struct radix_tree_root *root,
> return;
>
> if (update_node)
> - update_node(node, private);
> + update_node(node);
>
> - delete_node(root, node, update_node, private);
> + delete_node(root, node, update_node);
> }
>
> /**
> @@ -1225,7 +1223,7 @@ void __radix_tree_replace(struct radix_tree_root *root,
> void radix_tree_replace_slot(struct radix_tree_root *root,
> void __rcu **slot, void *item)
> {
> - __radix_tree_replace(root, NULL, slot, item, NULL, NULL);
> + __radix_tree_replace(root, NULL, slot, item, NULL);
> }
> EXPORT_SYMBOL(radix_tree_replace_slot);
>
> @@ -1242,7 +1240,7 @@ void radix_tree_iter_replace(struct radix_tree_root *root,
> const struct radix_tree_iter *iter,
> void __rcu **slot, void *item)
> {
> - __radix_tree_replace(root, iter->node, slot, item, NULL, NULL);
> + __radix_tree_replace(root, iter->node, slot, item, NULL);
> }
>
> #ifdef CONFIG_RADIX_TREE_MULTIORDER
> @@ -1972,7 +1970,6 @@ EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
> * @root: radix tree root
> * @node: node containing @index
> * @update_node: callback for changing leaf nodes
> - * @private: private data to pass to @update_node
> *
> * After clearing the slot at @index in @node from radix tree
> * rooted at @root, call this function to attempt freeing the
> @@ -1980,10 +1977,9 @@ EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
> */
> void __radix_tree_delete_node(struct radix_tree_root *root,
> struct radix_tree_node *node,
> - radix_tree_update_node_t update_node,
> - void *private)
> + radix_tree_update_node_t update_node)
> {
> - delete_node(root, node, update_node, private);
> + delete_node(root, node, update_node);
> }
>
> static bool __radix_tree_delete(struct radix_tree_root *root,
> @@ -2001,7 +1997,7 @@ static bool __radix_tree_delete(struct radix_tree_root *root,
> node_tag_clear(root, node, tag, offset);
>
> replace_slot(slot, NULL, node, -1, exceptional);
> - return node && delete_node(root, node, NULL, NULL);
> + return node && delete_node(root, node, NULL);
> }
>
> /**
> diff --git a/mm/filemap.c b/mm/filemap.c
> index dba68e1d9869..e59580feefd9 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -35,6 +35,7 @@
> #include <linux/hugetlb.h>
> #include <linux/memcontrol.h>
> #include <linux/cleancache.h>
> +#include <linux/shmem_fs.h>
> #include <linux/rmap.h>
> #include "internal.h"
>
> @@ -134,7 +135,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
> *shadowp = p;
> }
> __radix_tree_replace(&mapping->page_tree, node, slot, page,
> - workingset_update_node, mapping);
> + workingset_lookup_update(mapping));
> mapping->nrpages++;
> return 0;
> }
> @@ -162,7 +163,7 @@ static void page_cache_tree_delete(struct address_space *mapping,
>
> radix_tree_clear_tags(&mapping->page_tree, node, slot);
> __radix_tree_replace(&mapping->page_tree, node, slot, shadow,
> - workingset_update_node, mapping);
> + workingset_lookup_update(mapping));
> }
>
> page->mapping = NULL;
> @@ -360,7 +361,7 @@ page_cache_tree_delete_batch(struct address_space *mapping, int count,
> }
> radix_tree_clear_tags(&mapping->page_tree, iter.node, slot);
> __radix_tree_replace(&mapping->page_tree, iter.node, slot, NULL,
> - workingset_update_node, mapping);
> + workingset_lookup_update(mapping));
> total_pages++;
> }
> mapping->nrpages -= total_pages;
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 07a1d22807be..a72f68aee6a4 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -338,7 +338,7 @@ static int shmem_radix_tree_replace(struct address_space *mapping,
> if (item != expected)
> return -ENOENT;
> __radix_tree_replace(&mapping->page_tree, node, pslot,
> - replacement, NULL, NULL);
> + replacement, NULL);
> return 0;
> }
>
> diff --git a/mm/truncate.c b/mm/truncate.c
> index 3dfa2d5e642e..d578d542a6ee 100644
> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -42,7 +42,7 @@ static void clear_shadow_entry(struct address_space *mapping, pgoff_t index,
> if (*slot != entry)
> goto unlock;
> __radix_tree_replace(&mapping->page_tree, node, slot, NULL,
> - workingset_update_node, mapping);
> + workingset_update_node);
> mapping->nrexceptional--;
> unlock:
> spin_unlock_irq(&mapping->tree_lock);
> diff --git a/mm/workingset.c b/mm/workingset.c
> index 7119cd745ace..0f7b4fb130e3 100644
> --- a/mm/workingset.c
> +++ b/mm/workingset.c
> @@ -339,14 +339,8 @@ void workingset_activation(struct page *page)
>
> static struct list_lru shadow_nodes;
>
> -void workingset_update_node(struct radix_tree_node *node, void *private)
> +void workingset_update_node(struct radix_tree_node *node)
> {
> - struct address_space *mapping = private;
> -
> - /* Only regular page cache has shadow entries */
> - if (dax_mapping(mapping) || shmem_mapping(mapping))
> - return;
> -
> /*
> * Track non-empty nodes that contain only shadow entries;
> * unlink those that contain pages or are being freed.
> @@ -474,7 +468,7 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
> goto out_invalid;
> inc_lruvec_page_state(virt_to_page(node), WORKINGSET_NODERECLAIM);
> __radix_tree_delete_node(&mapping->page_tree, node,
> - workingset_update_node, mapping);
> + workingset_lookup_update(mapping));
>
> out_invalid:
> spin_unlock(&mapping->tree_lock);
> diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
> index 06c71178d07d..59245b3d587c 100644
> --- a/tools/testing/radix-tree/multiorder.c
> +++ b/tools/testing/radix-tree/multiorder.c
> @@ -618,7 +618,7 @@ static void multiorder_account(void)
> __radix_tree_insert(&tree, 1 << 5, 5, (void *)0x12);
> __radix_tree_lookup(&tree, 1 << 5, &node, &slot);
> assert(node->count == node->exceptional * 2);
> - __radix_tree_replace(&tree, node, slot, NULL, NULL, NULL);
> + __radix_tree_replace(&tree, node, slot, NULL, NULL);
> assert(node->exceptional == 0);
>
> item_kill_tree(&tree);
> --
> 2.14.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR