Andrew Morton wrote:
Daniel Phillips <[email protected]> wrote:
assert_spin_locked(&dlm->spinlock);
+ bucket = dlm->lockres_hash + full_name_hash(name, len) % DLM_HASH_BUCKETS;
- hash = full_name_hash(name, len);
err, you might want to calculate that hash outside the spinlock.
Yah.
Maybe have a lock per bucket, too.
So the lock memory is as much as the hash table? ;-)
A 1MB hashtable is verging on comical. How may data are there in total?
Even with the 256K entry hash table, __dlm_lookup_lockres is still the
top systime gobbler:
-------------
real 31.01
user 25.29
sys 3.09
-------------
CPU: P4 / Xeon, speed 2793.37 MHz (estimated)
Counted GLOBAL_POWER_EVENTS events (time during which processor is not stopped) with a unit mask of 0x01 (mandatory) count 240000
samples % image name app name symbol name
-------------------------------------------------------------------------------
17071831 71.2700 libbz2.so.1.0.2 libbz2.so.1.0.2 (no symbols)
17071831 100.000 libbz2.so.1.0.2 libbz2.so.1.0.2 (no symbols) [self]
-------------------------------------------------------------------------------
2638066 11.0132 vmlinux vmlinux __dlm_lookup_lockres
2638066 100.000 vmlinux vmlinux __dlm_lookup_lockres [self]
-------------------------------------------------------------------------------
332683 1.3889 oprofiled oprofiled (no symbols)
332683 100.000 oprofiled oprofiled (no symbols) [self]
-------------------------------------------------------------------------------
254736 1.0634 vmlinux vmlinux ocfs2_local_alloc_count_bits
254736 100.000 vmlinux vmlinux ocfs2_local_alloc_count_bits [self]
-------------------------------------------------------------------------------
176794 0.7381 tar tar (no symbols)
176794 100.000 tar tar (no symbols) [self]
-------------------------------------------------------------------------------
Note, this is uniprocessor, single node on a local disk. Something
pretty badly broken all right. Tomorrow I will take a look at the hash
distribution and see what's up.
I guess there are about 250k symbols in the table before purging
finally kicks in, which happens 5th or 6th time I untar a kernel tree.
So, 20,000 names times 5-6 times the three locks per inode Mark
mentioned. I'll actually measure that tomorrow instead of inferring
it.
I think this table is per-ocfs2-mount, and really really, a meg is
nothing if it makes CPU cycles go away. That's .05% of the memory
on this box, which is a small box where clusters are concerned. But
there is also some gratuitous cpu suck still happening in there that
needs investigating. I would not be surprised at all to learn that
full_name_hash is a terrible hash function.
Regards,
Daniel
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