[PlanetCCRMA] kjournald configuration

Rick B zajelo3@cfl.rr.com
Tue Nov 9 11:21:01 2004

Juan Reyes wrote:

>I am trying to change the commit interval for kjournald from 5 seconds
>to something like 30.
>The reason is because I am having periodic and I should say constant
>disk access. This issue freezes other priority processes including X and
>thus mouse and keyboard.
>I am running planet kernels and Fedora on an HP laptop. As far as I been
>able to google it seems that I need to recompile a new kernel with a new
>value for the variable ¨journal->j_commit_interval ¨  in the file  ¨
>fs/jbd/journal.c ¨
>Has any of you had this problem, any suggestions ?
>  --* Juan 
>PlanetCCRMA mailing list
    Kjournald probably isn't your problem and if it is you wouldn't 
necessarily want to extend the time it writes journals to disk you would 
probably need to shorten it. If you wait 30 seconds to write the journal 
to disk that just means that there is going to be that much more to 
write to disk, thus creating longer disk write times. But I don't 
believe that's your problem as I've struggled with this issue before and 
tuning my virtual memory has always solved the problem. By tuning vm to 
write to disk more often in smaller chunks it will help if not cure your 
problem. How to tune vm is dependent on which kernel you are using, the 
2.4 is easier to me because there is more documentation. With the 2.6 
kernel it's harder as the powers that be switched how vm works on the 
2.6 kernel and the documentation is minimal. By the way if your using a 
2.6.9 kernel, there was a bug in kswapd that caused excessive disk 
thrashing, but I'm sure Fernando would have patched that by now :-)

                    Rick B