Re: clarification about redhat and vm

[Andrea Arcangeli]

On Fri, Jan 18, 2002 at 05:46:33PM +0100, Wilhelm Nuesser wrote:
> 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.

and I assume you were using either ext2 or reiserfs anyways, so the
fsync problem never affected you since the first place (also with older
kernels) I believe.

Andrea