From: Kuanling Huang <peterh@xxxxxxxxxxxx>
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 respectively if
simply send a large file.
Signed-off-by: Kuanling Huang <peterh@xxxxxxxxxxxx>
---
fs/btrfs/send.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 63a6152..ac67ff6 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4475,16 +4475,27 @@ 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);
- btrfs_force_ra(inode->i_mapping, &sctx->ra, NULL, index,
- last_index - index + 1);
while (index <= last_index) {
unsigned cur_len = min_t(unsigned, len,
PAGE_CACHE_SIZE - pg_offset);
- page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
+ 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_NOFS);
+ if (unlikely(!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)) {
--
1.9.1
--
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