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Btrfs: Improve metadata read latencies

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This fixes latency problems on metadata reads by making sure they
don't go through the async submit queue, and by tuning down the amount
of readahead done during btree searches.

Also, the btrfs bdi congestion function is tuned to ignore the
number of pending async bios and checksums pending.  There is additional
code that throttles new async bios now and the congestion function
doesn't need to worry about it anymore.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2008-11-13 09:59:36 -05:00
parent 5b050f04c8
commit 6f3577bdc7
2 changed files with 7 additions and 7 deletions
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8
fs/btrfs/ctree.c
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@@ -1285,16 +1285,16 @@ static noinline void reada_for_search(struct btrfs_root *root,
}
search = btrfs_node_blockptr(node, nr);
if ((search >= lowest_read && search <= highest_read) ||
(search < lowest_read && lowest_read - search <= 32768) ||
(search > highest_read && search - highest_read <= 32768)) {
(search < lowest_read && lowest_read - search <= 16384) ||
(search > highest_read && search - highest_read <= 16384)) {
readahead_tree_block(root, search, blocksize,
btrfs_node_ptr_generation(node, nr));
nread += blocksize;
}
nscan++;
if (path->reada < 2 && (nread > (256 * 1024) || nscan > 32))
if (path->reada < 2 && (nread > (64 * 1024) || nscan > 32))
break;
if(nread > (1024 * 1024) || nscan > 128)
if(nread > (256 * 1024) || nscan > 128)
break;
if (search < lowest_read)