[Ocfs2-devel] [PATCH] Dynamic lockres hash table

[Jan Kara]

On Wed 05-03-08 10:41:34, Sunil Mushran wrote:
> Jan Kara wrote:
>>   Actually, it's non-trivial to measure (differently than by profiling).
>> You cannot use standard time functions because they have too low 
>> resolution
>> - we are speaking about microseconds here...
>>   
> jiffies should have enough resolution.
  Not really. On SLES kernels HZ=250 and thus 1 jiffie tick is 4ms. That's
quite a lot - actually, my lockres statistics show that quite a lot of lock
operations get below 4 ms (i.e., time for that acquisition was counted as
0). I guess they are operations that don't require any network
communication...

>>   Definitely, they should have 16 or even 32 pages per mount.  With 500K
>> lockres, which is not so extreme on bigger FS, 16 pages mean hash chains 
>> of
>> average length 61 on x86_64. It is not ideal but I guess it should be
>> sufficient.
>
> Any objections to increasing the default to 32 pages for 1.4?
  32 pages is fine with me.

								Honza
-- 
Jan Kara <jack at suse.cz>
SUSE Labs, CR