Re: [PATCH]: adding counters to count bytes read/written

[Manik Raina]

	Thanks for the comments Matti, Please see inline ...

Matti Aarnio wrote:
> 
> On Mon, May 20, 2002 at 03:09:36PM +0530, Manik Raina wrote:
> > Hi Linus,
> >
> >       This patch adds 2 counters to the task_struct for
> >       counting how many bytes were read/written using
> >       the read()/write() system calls.
> >
> >       These counters may be useful in determining how
> >       many IO requests are made by each process.
> 
>   These are defined as UINTegers, are you sure that is appropriate type ?
>   What to do when they will overflow ?  For short term activity tracking
>   they may be ok (4GB/200 MB/sec = 20 sec to wrap around), but for accounting
>   the overflow might not be liked thing..

	How about 64 bit counters ? i feel those should go on without
	wraparound for a _very_ long time.

	Did you have anything else in mind ?
	
> 
>   For short-term IO-activity tracking they may indeed make sense, but I
>   would add another pair of counters to assist on that tracking.  Namely
>   "values at the end of previous interval", which are maintained by the
>   activity tracking code.

	Would this still be required if the counters are 64 bit ?

> 
>   Reading one byte at the time won't grow those counters very fast, but will
>   cause massive amounts of syscalls, and context switches, so tracking data
>   amount alone isn't good enough.

	What else would you suggest i track ?
	thanks
	Manik

> 
> ....
> > diff -u -r ../temp/linux-2.5.12/include/linux/sched.h ./include/linux/sched.h
> > --- ../temp/linux-2.5.12/include/linux/sched.h        Wed May  1 05:38:47 2002
> > +++ ./include/linux/sched.h   Mon May 20 09:25:32 2002
> > @@ -315,6 +315,7 @@
> >       int link_count, total_link_count;
> >       struct tty_struct *tty; /* NULL if no tty */
> >       unsigned int locks; /* How many file locks are being held */
> > +     unsigned int bytes_written, bytes_read;
> >  /* ipc stuff */
> >       struct sysv_sem sysvsem;
> >  /* CPU-specific state of this task */
> 
> /Matti Aarnio