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Btrfs: Add async worker threads for pre and post IO checksumming

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Btrfs has been using workqueues to spread the checksumming load across
other CPUs in the system.  But, workqueues only schedule work on the
same CPU that queued the work, giving them a limited benefit for systems with
higher CPU counts.

This code adds a generic facility to schedule work with pools of kthreads,
and changes the bio submission code to queue bios up.  The queueing is
important to make sure large numbers of procs on the system don't
turn streaming workloads into random workloads by sending IO down
concurrently.

The end result of all of this is much higher performance (and CPU usage) when
doing checksumming on large machines.  Two worker pools are created,
one for writes and one for endio processing.  The two could deadlock if
we tried to service both from a single pool.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2008-06-11 16:50:36 -04:00
parent 43e570b08a
commit 8b71284292
8 changed files with 625 additions and 131 deletions
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4
fs/btrfs/inode.c
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@@ -359,7 +359,7 @@ int __btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
kfree(sums);
return btrfs_map_bio(root, rw, bio, mirror_num);
return btrfs_map_bio(root, rw, bio, mirror_num, 1);
}
int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
@@ -383,7 +383,7 @@ int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
inode, rw, bio, mirror_num,
__btrfs_submit_bio_hook);
mapit:
return btrfs_map_bio(root, rw, bio, mirror_num);
return btrfs_map_bio(root, rw, bio, mirror_num, 0);
}
int btrfs_readpage_io_hook(struct page *page, u64 start, u64 end)