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From Suresh Thalamati <tsur...@Source-Zone.org>
Subject Re: java1.4.2 "rws" mode - log write performance - OSX numbers
Date Tue, 07 Sep 2004 21:40:34 GMT
Joseph Grace wrote:

> Suresh:
>
>> Does Mac  OS  has concept of write cache enabling  ?   Numbers below
>> are with write cache enabled/disabled ?
>
>
> Yes, OSX has write cache enabling.  Presumably it's on by default 
> (though I admit to not knowing how to confirm that), so my numbers 
> include it.  That's why I ran the test under a variety of 
> circumstances.  Benchmarks are hard, and the numbers vary a lot, so I 
> flagged the variance.  I'm not sure what all the factors are, but I 
> believe your (implied) suspicion that cache'ing is one such factor.
>
> = Joe =
>

Yes, trying to find out the write cache factor in  "rws"/"rwd" 
performance numbers.  What I observerd is on Win2k  i
when write cache is enabled  "rws" mode  does not seem to sync 
immediately to the disk unlike FileDescriptor.sync();  I think  this
is ok  because user  has chosen the write cache enabling option.  When 
write cache is disabled on windows the "rws" mode
write does seem to perform the sync.(Note: On JDK141 sycn does not  
happen this case also).

 I don't  have much knoweledge of jvm internals ,  but if the expected 
behaviour  jvm on  MAC OS  is similar
 to Windows,  write performance numbers in "rws/rwd"  mode won't  be 
accurate when  write cache is enabled.
I also don't know how to disable the write cache on Mac.  Can't really 
say "rws" does not sync for sure  on Mac
unless the write cache is disabled. 


-suresht




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