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mm: optimize invalidation of shadow entries

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The kernel invalidates the page cache in batches of PAGEVEC_SIZE.  For
each batch, it traverses the page cache tree and collects the entries
(folio and shadow entries) in the struct folio_batch.  For the shadow
entries present in the folio_batch, it has to traverse the page cache tree
for each individual entry to remove them.  This patch optimize this by
removing them in a single tree traversal.

To evaluate the changes, we created 200GiB file on a fuse fs and in a
memcg.  We created the shadow entries by triggering reclaim through
memory.reclaim in that specific memcg and measure the simple
fadvise(DONTNEED) operation.

 # time xfs_io -c 'fadvise -d 0 ${file_size}' file

              time (sec)
Without       5.12 +- 0.061
With-patch    4.19 +- 0.086 (18.16% decrease)

Link: https://lkml.kernel.org/r/20240925224716.2904498-3-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Chris Mason <clm@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Shakeel Butt 2024-09-25 15:47:16 -07:00 committed by Andrew Morton
parent cb8e64be76
commit d3db2c0425
1 changed files with 18 additions and 28 deletions
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46
mm/truncate.c
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@ -23,42 +23,28 @@
#include <linux/rmap.h>
#include "internal.h"
/*
* Regular page slots are stabilized by the page lock even without the tree
* itself locked. These unlocked entries need verification under the tree
* lock.
*/
static inline void __clear_shadow_entry(struct address_space *mapping,
pgoff_t index, void *entry)
{
XA_STATE(xas, &mapping->i_pages, index);
xas_set_update(&xas, workingset_update_node);
if (xas_load(&xas) != entry)
return;
xas_store(&xas, NULL);
}
static void clear_shadow_entries(struct address_space *mapping,
struct folio_batch *fbatch, pgoff_t *indices)
unsigned long start, unsigned long max)
{
int i;
XA_STATE(xas, &mapping->i_pages, start);
struct folio *folio;
/* Handled by shmem itself, or for DAX we do nothing. */
if (shmem_mapping(mapping) || dax_mapping(mapping))
return;
xas_set_update(&xas, workingset_update_node);
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
for (i = 0; i < folio_batch_count(fbatch); i++) {
struct folio *folio = fbatch->folios[i];
xas_lock_irq(&xas);
/* Clear all shadow entries from start to max */
xas_for_each(&xas, folio, max) {
if (xa_is_value(folio))
__clear_shadow_entry(mapping, indices[i], folio);
xas_store(&xas, NULL);
}
xa_unlock_irq(&mapping->i_pages);
xas_unlock_irq(&xas);
if (mapping_shrinkable(mapping))
inode_add_lru(mapping->host);
spin_unlock(&mapping->host->i_lock);
@ -481,7 +467,9 @@ unsigned long mapping_try_invalidate(struct address_space *mapping,
folio_batch_init(&fbatch);
while (find_lock_entries(mapping, &index, end, &fbatch, indices)) {
for (i = 0; i < folio_batch_count(&fbatch); i++) {
int nr = folio_batch_count(&fbatch);
for (i = 0; i < nr; i++) {
struct folio *folio = fbatch.folios[i];
/* We rely upon deletion not changing folio->index */
@ -508,7 +496,7 @@ unsigned long mapping_try_invalidate(struct address_space *mapping,
}
if (xa_has_values)
clear_shadow_entries(mapping, &fbatch, indices);
clear_shadow_entries(mapping, indices[0], indices[nr-1]);
folio_batch_remove_exceptionals(&fbatch);
folio_batch_release(&fbatch);
@ -612,7 +600,9 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
folio_batch_init(&fbatch);
index = start;
while (find_get_entries(mapping, &index, end, &fbatch, indices)) {
for (i = 0; i < folio_batch_count(&fbatch); i++) {
int nr = folio_batch_count(&fbatch);
for (i = 0; i < nr; i++) {
struct folio *folio = fbatch.folios[i];
/* We rely upon deletion not changing folio->index */
@ -658,7 +648,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
}
if (xa_has_values)
clear_shadow_entries(mapping, &fbatch, indices);
clear_shadow_entries(mapping, indices[0], indices[nr-1]);
folio_batch_remove_exceptionals(&fbatch);
folio_batch_release(&fbatch);