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Btrfs: Fix streaming read performance with checksumming on 

Large streaming reads make for large bios, which means each entry on the
list async work queues represents a large amount of data.  IO
congestion throttling on the device was kicking in before the async
worker threads decided a single thread was busy and needed some help.

The end result was that a streaming read would result in a single CPU
running at 100% instead of balancing the work off to other CPUs.

This patch also changes the pre-IO checksum lookup done by reads to
work on a per-bio basis instead of a per-page.  This results in many
extra btree lookups on large streaming reads.  Doing the checksum lookup
right before bio submit allows us to reuse searches while processing
adjacent offsets.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
hifive-unleashed-5.1
Chris Mason 2008-07-31 15:42:53 -04:00
parent 37d1aeee39
commit 61b4944018
5 changed files with 99 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/btrfs/async-thread.c
View File

@ -160,7 +160,7 @@ void btrfs_init_workers(struct btrfs_workers *workers, int max)
INIT_LIST_HEAD(&workers->idle_list);
spin_lock_init(&workers->lock);
workers->max_workers = max;
workers->idle_thresh = 64;
workers->idle_thresh = 32;
}
/*

2
fs/btrfs/ctree.h
View File

@ -1613,6 +1613,8 @@ int btrfs_lookup_inode(struct btrfs_trans_handle *trans, struct btrfs_root
struct btrfs_key *location, int mod);
/* file-item.c */
int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
struct bio *bio);
int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
u64 objectid, u64 pos, u64 disk_offset,

15
fs/btrfs/disk-io.c
View File

@ -1357,10 +1357,25 @@ struct btrfs_root *open_ctree(struct super_block *sb,
*/
btrfs_init_workers(&fs_info->workers, fs_info->thread_pool_size);
btrfs_init_workers(&fs_info->submit_workers, fs_info->thread_pool_size);
/* a higher idle thresh on the submit workers makes it much more
* likely that bios will be send down in a sane order to the
* devices
*/
fs_info->submit_workers.idle_thresh = 64;
btrfs_init_workers(&fs_info->fixup_workers, 1);
btrfs_init_workers(&fs_info->endio_workers, fs_info->thread_pool_size);
btrfs_init_workers(&fs_info->endio_write_workers,
fs_info->thread_pool_size);
/*
* endios are largely parallel and should have a very
* low idle thresh
*/
fs_info->endio_workers.idle_thresh = 4;
fs_info->endio_write_workers.idle_thresh = 4;
btrfs_start_workers(&fs_info->workers, 1);
btrfs_start_workers(&fs_info->submit_workers, 1);
btrfs_start_workers(&fs_info->fixup_workers, 1);

77
fs/btrfs/file-item.c
View File

@ -134,6 +134,83 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
return ret;
}
int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
struct bio *bio)
{
u32 sum;
struct bio_vec *bvec = bio->bi_io_vec;
int bio_index = 0;
u64 offset;
u64 item_start_offset = 0;
u64 item_last_offset = 0;
u32 diff;
int ret;
struct btrfs_path *path;
struct btrfs_csum_item *item = NULL;
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
path = btrfs_alloc_path();
path->reada = 2;
WARN_ON(bio->bi_vcnt <= 0);
while(bio_index < bio->bi_vcnt) {
offset = page_offset(bvec->bv_page) + bvec->bv_offset;
ret = btrfs_find_ordered_sum(inode, offset, &sum);
if (ret == 0)
goto found;
if (!item || offset < item_start_offset ||
offset >= item_last_offset) {
struct btrfs_key found_key;
u32 item_size;
if (item)
btrfs_release_path(root, path);
item = btrfs_lookup_csum(NULL, root, path,
inode->i_ino, offset, 0);
if (IS_ERR(item)) {
ret = PTR_ERR(item);
if (ret == -ENOENT || ret == -EFBIG)
ret = 0;
sum = 0;
printk("no csum found for inode %lu start "
"%llu\n", inode->i_ino,
(unsigned long long)offset);
goto found;
}
btrfs_item_key_to_cpu(path->nodes[0], &found_key,
path->slots[0]);
item_start_offset = found_key.offset;
item_size = btrfs_item_size_nr(path->nodes[0],
path->slots[0]);
item_last_offset = item_start_offset +
(item_size / BTRFS_CRC32_SIZE) *
root->sectorsize;
item = btrfs_item_ptr(path->nodes[0], path->slots[0],
struct btrfs_csum_item);
}
/*
* this byte range must be able to fit inside
* a single leaf so it will also fit inside a u32
*/
diff = offset - item_start_offset;
diff = diff / root->sectorsize;
diff = diff * BTRFS_CRC32_SIZE;
read_extent_buffer(path->nodes[0], &sum,
(unsigned long)item + diff,
BTRFS_CRC32_SIZE);
found:
set_state_private(io_tree, offset, sum);
bio_index++;
bvec++;
}
btrfs_free_path(path);
return 0;
}
int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
struct bio *bio)
{

57
fs/btrfs/inode.c
View File

@ -374,6 +374,10 @@ int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
BUG_ON(ret);
if (!(rw & (1 << BIO_RW))) {
if (!btrfs_test_opt(root, NODATASUM) &&
!btrfs_test_flag(inode, NODATASUM)) {
btrfs_lookup_bio_sums(root, inode, bio);
}
goto mapit;
}
@ -598,58 +602,6 @@ int btrfs_writepage_end_io_hook(struct page *page, u64 start, u64 end,
return btrfs_finish_ordered_io(page->mapping->host, start, end);
}
int btrfs_readpage_io_hook(struct page *page, u64 start, u64 end)
{
int ret = 0;
struct inode *inode = page->mapping->host;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
struct btrfs_csum_item *item;
struct btrfs_path *path = NULL;
u32 csum;
if (btrfs_test_opt(root, NODATASUM) ||
btrfs_test_flag(inode, NODATASUM))
return 0;
/*
* It is possible there is an ordered extent that has
* not yet finished for this range in the file. If so,
* that extent will have a csum cached, and it will insert
* the sum after all the blocks in the extent are fully
* on disk. So, look for an ordered extent and use the
* sum if found. We have to do this before looking in the
* btree because csum items are pre-inserted based on
* the file size. btrfs_lookup_csum might find an item
* that still hasn't been fully filled.
*/
ret = btrfs_find_ordered_sum(inode, start, &csum);
if (ret == 0)
goto found;
ret = 0;
path = btrfs_alloc_path();
item = btrfs_lookup_csum(NULL, root, path, inode->i_ino, start, 0);
if (IS_ERR(item)) {
ret = PTR_ERR(item);
/* a csum that isn't present is a preallocated region. */
if (ret == -ENOENT || ret == -EFBIG)
ret = 0;
csum = 0;
printk("no csum found for inode %lu start %Lu\n", inode->i_ino,
start);
goto out;
}
read_extent_buffer(path->nodes[0], &csum, (unsigned long)item,
BTRFS_CRC32_SIZE);
found:
set_state_private(io_tree, start, csum);
out:
if (path)
btrfs_free_path(path);
return ret;
}
struct io_failure_record {
struct page *page;
u64 start;
@ -3613,7 +3565,6 @@ static struct extent_io_ops btrfs_extent_io_ops = {
.fill_delalloc = run_delalloc_range,
.submit_bio_hook = btrfs_submit_bio_hook,
.merge_bio_hook = btrfs_merge_bio_hook,
.readpage_io_hook = btrfs_readpage_io_hook,
.readpage_end_io_hook = btrfs_readpage_end_io_hook,
.writepage_end_io_hook = btrfs_writepage_end_io_hook,
.writepage_start_hook = btrfs_writepage_start_hook,