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Btrfs: Reduce contention on the root node

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This calls unlock_up sooner in btrfs_search_slot in order to decrease the
amount of work done with the higher level tree locks held.

Also, it changes btrfs_tree_lock to spin for a big against the page lock
before scheduling.  This makes a big difference in context switch rate under
highly contended workloads.

Longer term, a better locking structure is needed than the page lock.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2008-06-25 16:14:04 -04:00
parent 3f157a2fd2
commit f9efa9c784
2 changed files with 21 additions and 6 deletions
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10
fs/btrfs/locking.c
View file

@ -27,6 +27,16 @@
int btrfs_tree_lock(struct extent_buffer *eb)
{
int i;
if (!TestSetPageLocked(eb->first_page))
return 0;
for (i = 0; i < 512; i++) {
cpu_relax();
if (!TestSetPageLocked(eb->first_page))
return 0;
}
cpu_relax();
lock_page(eb->first_page);
return 0;
}