Re: What is rw_vm

["Shourya P. Bhattacharya" <sbhattacharya@xxxxxxxxx>]

Hi,
> >
> > The symbol rw_vm is recurring and seems to be consuming lots of time.
> > As I don't know what rw_vm does, and I can't find this symbol in the
> > sources, I can't understand what's happening in the system.
> >
> > Could someone explain me what rw_vm is ? And maybe tell me to what part
> > of the kernel code it's related ?
> >
> > My system runs a 2.6.9 kernel with smp enabled.
> 
> rw_vm is a fedora specific routine that basically is the workhorse for
> copy_from_user and copy_to_user and friends...

I suggest you try compiling your kernel in UNI mode and then look at
the percentage of time spent in  rw_vm.  Compare  the  percentage of
time spent in rw_vm in both SMP  and UNI kernels. If there is big
difference, it is quite possible that cache line bouncing  is taking
place  between  processors  causing  a large overhead for the  copy
routines.
Do share  your experience, I would be interested in the result.

Shourya

--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive:       http://mail.nl.linux.org/kernelnewbies/
FAQ:           http://kernelnewbies.org/faq/