Btrfs: send, apply asynchronous page cache readahead to enhance page read
By analyzing the perf on btrfs send, we found it take large amount of
cpu time on page_cache_sync_readahead. This effort can be reduced after
switching to asynchronous one. Overall performance gain on HDD and SSD
were 9 and 15 percent if simply send a large file.
Signed-off-by: Kuanling Huang <peterh@synology.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 07445be..0746eda 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4720,16 +4720,27 @@ static ssize_t fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len)
/* initial readahead */
memset(&sctx->ra, 0, sizeof(struct file_ra_state));
file_ra_state_init(&sctx->ra, inode->i_mapping);
- page_cache_sync_readahead(inode->i_mapping, &sctx->ra, NULL, index,
- last_index - index + 1);
while (index <= last_index) {
unsigned cur_len = min_t(unsigned, len,
PAGE_SIZE - pg_offset);
- page = find_or_create_page(inode->i_mapping, index, GFP_KERNEL);
+
+ page = find_lock_page(inode->i_mapping, index);
if (!page) {
- ret = -ENOMEM;
- break;
+ page_cache_sync_readahead(inode->i_mapping, &sctx->ra,
+ NULL, index, last_index + 1 - index);
+
+ page = find_or_create_page(inode->i_mapping, index,
+ GFP_KERNEL);
+ if (!page) {
+ ret = -ENOMEM;
+ break;
+ }
+ }
+
+ if (PageReadahead(page)) {
+ page_cache_async_readahead(inode->i_mapping, &sctx->ra,
+ NULL, page, index, last_index + 1 - index);
}
if (!PageUptodate(page)) {
