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readahead: use ilog2 instead of a while loop in page_cache_ra_order()

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A while loop is used to adjust the new_order to be lower than the
ra->size.  ilog2 could be used to do the same instead of using a loop.

ilog2 typically resolves to a bit scan reverse instruction.  This is
particularly useful when ra->size is smaller than the 2^new_order as it
resolves in one instruction instead of looping to find the new_order.

No functional changes.

Link: https://lkml.kernel.org/r/20240115102523.2336742-1-kernel@pankajraghav.com
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pankaj Raghav 2024-01-15 11:25:22 +01:00 committed by Andrew Morton
parent cabbb6d51e
commit e03c16fb4a
1 changed files with 2 additions and 4 deletions
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6
mm/readahead.c
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@ -500,10 +500,8 @@ void page_cache_ra_order(struct readahead_control *ractl,
if (new_order < MAX_PAGECACHE_ORDER) {
new_order += 2;
if (new_order > MAX_PAGECACHE_ORDER)
new_order = MAX_PAGECACHE_ORDER;
while ((1 << new_order) > ra->size)
new_order--;
new_order = min_t(unsigned int, MAX_PAGECACHE_ORDER, new_order);
new_order = min_t(unsigned int, new_order, ilog2(ra->size));
}
filemap_invalidate_lock_shared(mapping);