Re: [PATCH] dentry and inode cache hash algorithm performance changes.

["Jose R. Santos" <jrsantos@austin.ibm.com>]

On 05/04/04 13:55:10, Andrew Morton wrote:
> > Andrew - Is there any workload you want me to run to show that this hash
> > function is going to be equal or better that the one already provided
> > in Linux?
> 
> Not really - it sounds like you've covered it pretty well.  Did you try SDET?
> 
> It could be that reducing the hash table size will turn pretty much any
> workload into a test of the hash quality.

Sorry for the late reply...

Steve Pratt seem to have a SDET setup already and he did me the favor of 
running SDET with a reduce dentry entry hash table size.  I belive that
his table suggest that less than 3% change is acceptable variability, but
overall he got a 5% better number using the new hash algorith.

-JRS

=========================================================================
A) x4408way1.sdet.2.6.5100000-8p.04-05-05_12.08.44 vs 
B) x4408way1.sdet.2.6.5+hash-100000-8p.04-05-05_11.48.02


<6>Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)
<4>Inode-cache hash table entries: 1048576 (order: 10, 4194304 bytes) 

Results:Throughput 

                                          tolerance = 0.00 + 3.00% of A
                      A            B
   Threads      Ops/sec      Ops/sec    %diff         diff    tolerance
---------- ------------ ------------ -------- ------------ ------------
         1    4341.9300    4401.9500     1.38        60.02       130.26 
         2    8242.2000    8165.1200    -0.94       -77.08       247.27 
         4   15274.4900   15257.1000    -0.11       -17.39       458.23 
         8   21326.9200   21320.7000    -0.03        -6.22       639.81 
        16   23056.2100   24282.8000     5.32      1226.59       691.69  * 
        32   23397.2500   24684.6100     5.50      1287.36       701.92  * 
        64   23372.7600   23632.6500     1.11       259.89       701.18 
       128   17009.3900   16651.9600    -2.10      -357.43       510.28 
=========================================================================