Re: clarification about redhat and vm

[Wilhelm Nuesser <wilhelm.nuesser@sap.com>]

Alan Cox wrote:

>>"If redhat doesn't use the -aa VM " was a short form of "if redhat
>>cannot see the goodness of all the bugfixing work that happened between
>>the 2.4.9 VM and any current branch 2.4, and so if they keep shipping
>>2.4.9 VM as the best one for DBMS and critical VM apps like the SAP
>>benchmark".
>>
>
>The RH VM is totally unrelated to the crap in 2.4.9 vanilla. The SAP comment
>begs a question. 2.4.10 seems to have problems remembering to actually 
>do fsync()'s. How much of your SAP benchmark is from fsync's that dont
>happen ? Do you get the same values with 2.4.18-aa ?
>
Well, basically we checked the thing many times with quite different 
kernels.
Our current tests - which show exactly the same results as 
2.4.[10,14,15] - run
on the new "official" SuSE kernel 2.4.16.  Again, we  observe a 
performance increase
in high swap situations of about  a factor of ten compared to 2.4.[7,9].
 
IMO, this shows that errors like fsync etc. are _not_ responsible for 
the improved
performance.


But of course, we will check the newer kernels as well.  I think we 
could live with another
factor of ten ...

Best regards
    Willi

-----------------------

   Willi Nüßer
    SAP LinuxLab