diff options
| author | Jan Kara <jack@suse.cz> | 2024-06-25 13:18:57 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-07-04 05:30:27 +0300 |
| commit | 0b1efc3e78d12278a8c0f2c665d66564a2cb965f (patch) | |
| tree | ff4cb81950e837b23618c822947ffc206b99e837 /mm | |
| parent | 8eaf93ac70f3e1bbbe7e28a4f34289ef2d0d0bef (diff) | |
| download | linux-0b1efc3e78d12278a8c0f2c665d66564a2cb965f.tar.xz | |
readahead: drop dead code in ondemand_readahead()
ondemand_readahead() scales up the readahead window if the current read
would hit the readahead mark placed by itself. However the condition is
mostly dead code because:
a) In case of async readahead we always increase ra->start so ra->start
== index is never true.
b) In case of sync readahead we either go through
try_context_readahead() in which case ra->async_size == 1 < ra->size or
we go through initial_readahead where ra->async_size == ra->size iff
ra->size == max_pages.
So the only practical effect is reducing async_size for large initial
reads. Make the code more obvious.
Link: https://lkml.kernel.org/r/20240625101909.12234-7-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Tested-by: Zhang Peng <zhangpengpeng0808@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/readahead.c | 21 |
1 files changed, 2 insertions, 19 deletions
diff --git a/mm/readahead.c b/mm/readahead.c index 9ea5125a0dce..d92a5e8d89c4 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -549,7 +549,6 @@ static void ondemand_readahead(struct readahead_control *ractl, struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host); struct file_ra_state *ra = ractl->ra; unsigned long max_pages = ra->ra_pages; - unsigned long add_pages; pgoff_t index = readahead_index(ractl); pgoff_t expected, prev_index; unsigned int order = folio ? folio_order(folio) : 0; @@ -638,26 +637,10 @@ static void ondemand_readahead(struct readahead_control *ractl, initial_readahead: ra->start = index; ra->size = get_init_ra_size(req_size, max_pages); - ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size; + ra->async_size = ra->size > req_size ? ra->size - req_size : + ra->size >> 1; readit: - /* - * Will this read hit the readahead marker made by itself? - * If so, trigger the readahead marker hit now, and merge - * the resulted next readahead window into the current one. - * Take care of maximum IO pages as above. - */ - if (index == ra->start && ra->size == ra->async_size) { - add_pages = get_next_ra_size(ra, max_pages); - if (ra->size + add_pages <= max_pages) { - ra->async_size = add_pages; - ra->size += add_pages; - } else { - ra->size = max_pages; - ra->async_size = max_pages >> 1; - } - } - ractl->_index = ra->start; page_cache_ra_order(ractl, ra, order); } |