From 2131bcd38b18167f499f190acf3409dfe5b3c280 Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Wed, 5 Mar 2014 10:07:35 +0800 Subject: [PATCH] Btrfs: add readahead for send_write Btrfs send reads data from disk and then writes to a stream via pipe or a file via flush. Currently we're going to read each page a time, so every page results in a disk read, which is not friendly to disks, esp. HDD. Given that, the performance can be gained by adding readahead for those pages. Here is a quick test: $ btrfs subvolume create send $ xfs_io -f -c "pwrite 0 1G" send/foobar $ btrfs subvolume snap -r send ro $ time "btrfs send ro -f /dev/null" w/o w real 1m37.527s 0m9.097s user 0m0.122s 0m0.086s sys 0m53.191s 0m12.857s Signed-off-by: Liu Bo Reviewed-by: David Sterba Signed-off-by: Josef Bacik --- fs/btrfs/send.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index 112eb647b5cd..646369179697 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -124,6 +124,8 @@ struct send_ctx { struct list_head name_cache_list; int name_cache_size; + struct file_ra_state ra; + char *read_buf; /* @@ -4170,6 +4172,13 @@ static ssize_t fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len) goto out; last_index = (offset + len - 1) >> PAGE_CACHE_SHIFT; + + /* 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); -- 2.20.1