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bd681513fa
The btrfs metadata btree is the source of significant lock contention, especially in the root node. This commit changes our locking to use a reader/writer lock. The lock is built on top of rw spinlocks, and it extends the lock tracking to remember if we have a read lock or a write lock when we go to blocking. Atomics count the number of blocking readers or writers at any given time. It removes all of the adaptive spinning from the old code and uses only the spinning/blocking hints inside of btrfs to decide when it should continue spinning. In read heavy workloads this is dramatically faster. In write heavy workloads we're still faster because of less contention on the root node lock. We suffer slightly in dbench because we schedule more often during write locks, but all other benchmarks so far are improved. Signed-off-by: Chris Mason <chris.mason@oracle.com>
62 lines
2.1 KiB
C
62 lines
2.1 KiB
C
/*
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* Copyright (C) 2008 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#ifndef __BTRFS_LOCKING_
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#define __BTRFS_LOCKING_
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#define BTRFS_WRITE_LOCK 1
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#define BTRFS_READ_LOCK 2
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#define BTRFS_WRITE_LOCK_BLOCKING 3
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#define BTRFS_READ_LOCK_BLOCKING 4
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int btrfs_tree_lock(struct extent_buffer *eb);
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int btrfs_tree_unlock(struct extent_buffer *eb);
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int btrfs_try_spin_lock(struct extent_buffer *eb);
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void btrfs_tree_read_lock(struct extent_buffer *eb);
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void btrfs_tree_read_unlock(struct extent_buffer *eb);
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void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb);
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void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw);
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void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw);
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void btrfs_assert_tree_locked(struct extent_buffer *eb);
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int btrfs_try_tree_read_lock(struct extent_buffer *eb);
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int btrfs_try_tree_write_lock(struct extent_buffer *eb);
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static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw)
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{
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if (rw == BTRFS_WRITE_LOCK || rw == BTRFS_WRITE_LOCK_BLOCKING)
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btrfs_tree_unlock(eb);
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else if (rw == BTRFS_READ_LOCK_BLOCKING)
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btrfs_tree_read_unlock_blocking(eb);
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else if (rw == BTRFS_READ_LOCK)
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btrfs_tree_read_unlock(eb);
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else
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BUG();
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}
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static inline void btrfs_set_lock_blocking(struct extent_buffer *eb)
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{
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btrfs_set_lock_blocking_rw(eb, BTRFS_WRITE_LOCK);
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}
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static inline void btrfs_clear_lock_blocking(struct extent_buffer *eb)
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{
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btrfs_clear_lock_blocking_rw(eb, BTRFS_WRITE_LOCK_BLOCKING);
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}
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#endif
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