Re: [PATCH] Add Documentation for FAIR_USER_SCHED sysfs files

[Dhaval Giani <dhaval@linux.vnet.ibm.com>]

On Tue, Dec 11, 2007 at 09:35:56PM -0800, Greg KH wrote:
> On Wed, Dec 12, 2007 at 08:08:36AM +0530, Dhaval Giani wrote:
> > 
> > This patch adds documentation about /sys/kernel/uids/<uid>/cpu_share
> > to Documentation/ABI.
> > 
> > Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
> > 
> > ---
> >  Documentation/ABI/testing/sysfs-kernel-uids |   10 ++++++++++
> >  1 files changed, 10 insertions(+)
> > 
> > Index: current/Documentation/ABI/testing/sysfs-kernel-uids
> > ===================================================================
> > --- /dev/null
> > +++ current/Documentation/ABI/testing/sysfs-kernel-uids
> > @@ -0,0 +1,10 @@
> > +What:		/sys/kernel/uids/<uid>/cpu_shares
> > +Date:		December 2007
> > +Contact:	Dhaval Giani <dhaval@linux.vnet.ibm.com>
> > +		Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
> > +Description:
> > +		The /sys/kernel/uids/<uid>/cpu_shares tunable is used
> > +		to set the cpu bandwidth a user is allowed. This is a
> > +		propotional value. What that means is that if there
> > +		are two users logged in, each with shares 1024, they
> > +		will get equal CPU bandwidth.
> 
> Hm, how about describing the units here?  Can you put "10" in each file
> and everyone will get the same share?  100?  1?  1024 seems like an odd
> "share" number.  Unless there is some other document you wish to refer
> people to do help describe these values?
> 

It is proportional. That is, if two users have same value for shares,
they will get equal bandwidth on the CPU. If they are in the ratio 1:2,
then they will share it in that ratio. I've updated the patch for this.
Hope it is clearer.

Thanks,
--

This patch adds documentation about /sys/kernel/uids/<uid>/cpu_share
to Documentation/ABI.

Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>

---
 Documentation/ABI/testing/sysfs-kernel-uids |   14 ++++++++++++++
 1 files changed, 14 insertions(+)

Index: current/Documentation/ABI/testing/sysfs-kernel-uids
===================================================================
--- /dev/null
+++ current/Documentation/ABI/testing/sysfs-kernel-uids
@@ -0,0 +1,14 @@
+What:		/sys/kernel/uids/<uid>/cpu_shares
+Date:		December 2007
+Contact:	Dhaval Giani <dhaval@linux.vnet.ibm.com>
+		Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
+Description:
+		The /sys/kernel/uids/<uid>/cpu_shares tunable is used
+		to set the cpu bandwidth a user is allowed. This is a
+		propotional value. What that means is that if there
+		are two users logged in, each with an equal number of
+		shares, then they will get equal CPU bandwidth. Another
+		example would be, if User A has shares = 1024 and user
+		B has shares = 2048, User B will get twice the CPU
+		bandwidth user A will. For more details refer
+		Documentation/sched-design-CFS.txt

-- 
regards,
Dhaval