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radix-tree: delete radix_tree_range_tag_if_tagged()

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This is an exceptionally complicated function with just one caller
(tag_pages_for_writeback).  We devote a large portion of the runtime of
the test suite to testing this one function which has one caller.  By
introducing the new function radix_tree_iter_tag_set(), we can eliminate
all of the complexity while keeping the performance.  The caller can now
use a fairly standard radix_tree_for_each() loop, and it doesn't need to
worry about tricksy things like 'start' wrapping.

The test suite continues to spend a large amount of time investigating
this function, but now it's testing the underlying primitives such as
radix_tree_iter_resume() and the radix_tree_for_each_tagged() iterator
which are also used by other parts of the kernel.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Matthew Wilcox <[email protected]>
Tested-by: Kirill A. Shutemov <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Matthew Wilcox 2016-12-14 15:08:55 -08:00 • committed by Linus Torvalds
commit 268f42de71
9 changed files with 125 additions and 163 deletions
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26
mm/page-writeback.c
View file

@ -2106,18 +2106,26 @@ void tag_pages_for_writeback(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
#define WRITEBACK_TAG_BATCH 4096
unsigned long tagged;
unsigned long tagged = 0;
struct radix_tree_iter iter;
void **slot;
do {
spin_lock_irq(&mapping->tree_lock);
tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
&start, end, WRITEBACK_TAG_BATCH,
PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
spin_lock_irq(&mapping->tree_lock);
radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, start,
PAGECACHE_TAG_DIRTY) {
if (iter.index > end)
break;
radix_tree_iter_tag_set(&mapping->page_tree, &iter,
PAGECACHE_TAG_TOWRITE);
tagged++;
if ((tagged % WRITEBACK_TAG_BATCH) != 0)
continue;
slot = radix_tree_iter_resume(slot, &iter);
spin_unlock_irq(&mapping->tree_lock);
WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
cond_resched();
/* We check 'start' to handle wrapping when end == ~0UL */
} while (tagged >= WRITEBACK_TAG_BATCH && start);
spin_lock_irq(&mapping->tree_lock);
}
spin_unlock_irq(&mapping->tree_lock);
}
EXPORT_SYMBOL(tag_pages_for_writeback);