On Fri, Feb 22, 2002 at 10:35:53AM -0800, Hanna Linder wrote:
> --On Friday, February 22, 2002 23:52:04 +0530 Dipankar Sarma <dipankar@...> wrote:
> > On Fri, Feb 22, 2002 at 09:18:41AM -0800, Hanna Linder wrote:
> >> 3.1% 3.5% 0.6us(1047us) 3.2us( 979us)(0.07%) 25499542 96.5% 3.5% 0% dcache_lock
> > IIUC, holding the dcache_lock while walking the path as long as
> > we can find things in cache should decrease the number of times
> > we grab dcache_lock, but it seems both 2.4.17 and fast-walk patch
> Well, I am actually adding holding the dcache_lock where
> it was not held before (instead of incrementing d_count). So my
> understanding is the dcache_lock contention should go up a little
> bit. Although perhaps there is more tuning that needs to happen.
That is not what I understood.
My point is this - if you are walking up /home/hanna/foo/mysql/blah,
in 2.4.17 you would have to do 6 d_lookup()s and thus acquire the
lock 6 times. If you hold the lock during cached lookups as long
as you can find them during walk and assuming all of them are in
cache, you will have only 1 acquisition of dcache_lock. But, yes,
the average lock hold time should increase.
Does this logic make sense or have I missed something ?
Dipankar Sarma <dipankar@...> http://lse.sourceforge.net
Linux Technology Center, IBM Software Lab, Bangalore, India.