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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 <bo.li.liu@oracle.com> Reviewed-by: David Sterba <dsterba@suse.cz> Signed-off-by: Josef Bacik <jbacik@fb.com>
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1 changed files with 9 additions and 0 deletions
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@ -124,6 +124,8 @@ struct send_ctx {
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struct list_head name_cache_list;
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int name_cache_size;
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struct file_ra_state ra;
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char *read_buf;
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/*
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@ -4170,6 +4172,13 @@ static ssize_t fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len)
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goto out;
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last_index = (offset + len - 1) >> PAGE_CACHE_SHIFT;
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/* initial readahead */
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memset(&sctx->ra, 0, sizeof(struct file_ra_state));
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file_ra_state_init(&sctx->ra, inode->i_mapping);
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btrfs_force_ra(inode->i_mapping, &sctx->ra, NULL, index,
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last_index - index + 1);
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while (index <= last_index) {
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unsigned cur_len = min_t(unsigned, len,
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PAGE_CACHE_SIZE - pg_offset);
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