mm, truncate: do not check mapping for every page being truncated

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.

Link: http://lkml.kernel.org/r/20171018075952.10627-3-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 8 insertions, 13 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index a470dd8cd05b..155370fc87f2 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;
@@ -359,7 +360,7 @@ page_cache_tree_delete_batch(struct address_space *mapping,
 		}
 		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 4a39a3150ee2..02a0c0466c78 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 b997c9de28f6..b7d616a3bbbe 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -340,14 +340,8 @@ out:
 
 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.
@@ -475,7 +469,7 @@ 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);