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authorNikolay Borisov <nborisov@suse.com>2018-11-29 19:41:31 +0300
committerDavid Sterba <dsterba@suse.com>2018-12-17 16:51:49 +0300
commit61ed3a144aa75e76a3b0f75c2f49c81435e74621 (patch)
tree805a03861d79339eed44394ebe54ccd32453cf8e /fs/btrfs
parent15c8276302c42ebf704b44578f25bc35dfdbde24 (diff)
downloadlinux-61ed3a144aa75e76a3b0f75c2f49c81435e74621.tar.xz
btrfs: Refactor main loop in extent_readpages
extent_readpages processes all pages in the readlist in batches of 16, this is implemented by a single for loop but thanks to an if condition the loop does 2 things based on whether we've filled the batch or not. Additionally due to the structure of the code there is an additional check which deals with partial batches. Streamline all of this by explicitly using two loops. The outter one is used to process all pages while the inner one just fills in the batch of 16 (currently). Due to this new structure the code guarantees that all pages are processed in the loop hence the code to deal with any leftovers is eliminated. This also enable the compiler to inline __extent_readpages: ./scripts/bloat-o-meter fs/btrfs/extent_io.o extent_io.for add/remove: 0/1 grow/shrink: 1/0 up/down: 660/-820 (-160) Function old new delta extent_readpages 476 1136 +660 __extent_readpages 820 - -820 Total: Before=44315, After=44155, chg -0.36% Signed-off-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs')
-rw-r--r--fs/btrfs/extent_io.c34
1 files changed, 14 insertions, 20 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 60526332b877..7b489988d811 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4094,42 +4094,36 @@ int extent_readpages(struct address_space *mapping, struct list_head *pages,
unsigned nr_pages)
{
struct bio *bio = NULL;
- unsigned page_idx;
unsigned long bio_flags = 0;
struct page *pagepool[16];
- struct page *page;
struct extent_map *em_cached = NULL;
struct extent_io_tree *tree = &BTRFS_I(mapping->host)->io_tree;
int nr = 0;
u64 prev_em_start = (u64)-1;
- for (page_idx = 0; page_idx < nr_pages; page_idx++) {
- page = list_entry(pages->prev, struct page, lru);
+ while (!list_empty(pages)) {
+ for (nr = 0; nr < ARRAY_SIZE(pagepool) && !list_empty(pages);) {
+ struct page *page = list_entry(pages->prev,
+ struct page, lru);
- prefetchw(&page->flags);
- list_del(&page->lru);
- if (add_to_page_cache_lru(page, mapping,
- page->index,
- readahead_gfp_mask(mapping))) {
- put_page(page);
- continue;
+ prefetchw(&page->flags);
+ list_del(&page->lru);
+ if (add_to_page_cache_lru(page, mapping, page->index,
+ readahead_gfp_mask(mapping))) {
+ put_page(page);
+ continue;
+ }
+
+ pagepool[nr++] = page;
}
- pagepool[nr++] = page;
- if (nr < ARRAY_SIZE(pagepool))
- continue;
__extent_readpages(tree, pagepool, nr, &em_cached, &bio,
- &bio_flags, &prev_em_start);
- nr = 0;
+ &bio_flags, &prev_em_start);
}
- if (nr)
- __extent_readpages(tree, pagepool, nr, &em_cached, &bio,
- &bio_flags, &prev_em_start);
if (em_cached)
free_extent_map(em_cached);
- BUG_ON(!list_empty(pages));
if (bio)
return submit_one_bio(bio, 0, bio_flags);
return 0;