[PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[Mikael Pettersson]

Clean up perfctr/virtual by using the new cpus_andnot() operation
instead of messing with cpus_complement() and a new temporary.

Signed-off-by: Mikael Pettersson <mikpe@csd.uu.se>

diff -ruN linux-2.6.7-rc3-mm1/drivers/perfctr/virtual.c linux-2.6.7-rc3-mm1.perfctr-update/drivers/perfctr/virtual.c
--- linux-2.6.7-rc3-mm1/drivers/perfctr/virtual.c	2004-06-09 19:38:38.000000000 +0200
+++ linux-2.6.7-rc3-mm1.perfctr-update/drivers/perfctr/virtual.c	2004-06-09 21:04:33.000000000 +0200
@@ -403,13 +403,11 @@
 		return -EFAULT;
 
 	if (control.cpu_control.nractrs || control.cpu_control.nrictrs) {
-		cpumask_t tmp, old_mask, new_mask, tmp1;
+		cpumask_t tmp, old_mask, new_mask;
 
 		tmp = perfctr_cpus_forbidden_mask;
-		cpus_complement(tmp1, tmp);
-		tmp = tmp1;
 		old_mask = tsk->cpus_allowed;
-		cpus_and(new_mask, old_mask, tmp);
+		cpus_andnot(new_mask, old_mask, tmp);
 
 		if (cpus_empty(new_mask))
 			return -EINVAL;

Re: [PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[Paul Jackson]

> Clean up perfctr/virtual by using the new cpus_andnot() operation

Neat.

Do you still need "tmp" ?  Perhaps you could further add the
following patch (untested, unbuilt, ...).

This saves copies and stack space for one cpumask (that's
512 bits on my SN2 systems).

Signed-off-by: Paul Jackson <pj@sgi.com>

Index: 2.6.7-rc3-mm1/drivers/perfctr/virtual.c
===================================================================
--- 2.6.7-rc3-mm1.orig/drivers/perfctr/virtual.c	2004-06-09 15:34:34.000000000 -0700
+++ 2.6.7-rc3-mm1/drivers/perfctr/virtual.c	2004-06-09 15:38:32.000000000 -0700
@@ -403,11 +403,10 @@
 		return -EFAULT;
 
 	if (control.cpu_control.nractrs || control.cpu_control.nrictrs) {
-		cpumask_t tmp, old_mask, new_mask;
+		cpumask_t old_mask, new_mask;
 
-		tmp = perfctr_cpus_forbidden_mask;
 		old_mask = tsk->cpus_allowed;
-		cpus_andnot(new_mask, old_mask, tmp);
+		cpus_andnot(new_mask, old_mask, perfctr_cpus_forbidden_mask);
 
 		if (cpus_empty(new_mask))
 			return -EINVAL;


-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373

Re: [PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[Paul Jackson]

Or ... pushing the point further ... one _could_ remove the old_mask as
well.  However I think this makes the code less clear, even if it does
save a stack copy of a cpumask_t.  So I'm of mixed feelings on this
patch, edging slightly toward negative.  Same utter lack of testing as
the previous patch.

Signed-off-by: Paul Jackson <pj@sgi.com>

Index: 2.6.7-rc3-mm1/drivers/perfctr/virtual.c
===================================================================
--- 2.6.7-rc3-mm1.orig/drivers/perfctr/virtual.c	2004-06-09 15:38:32.000000000 -0700
+++ 2.6.7-rc3-mm1/drivers/perfctr/virtual.c	2004-06-09 15:53:06.000000000 -0700
@@ -403,14 +403,14 @@
 		return -EFAULT;
 
 	if (control.cpu_control.nractrs || control.cpu_control.nrictrs) {
-		cpumask_t old_mask, new_mask;
+		cpumask_t new_mask;
 
-		old_mask = tsk->cpus_allowed;
-		cpus_andnot(new_mask, old_mask, perfctr_cpus_forbidden_mask);
+		cpus_andnot(new_mask, tsk->cpus_allowed,
+						perfctr_cpus_forbidden_mask);
 
 		if (cpus_empty(new_mask))
 			return -EINVAL;
-		if (!cpus_equal(new_mask, old_mask))
+		if (!cpus_equal(tsk->cpus_allowed, new_mask))
 			set_cpus_allowed(tsk, new_mask);
 	}
 


-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373

Re: [PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[Mikael Pettersson]

Paul Jackson writes:
 > > Clean up perfctr/virtual by using the new cpus_andnot() operation
 > 
 > Neat.
 > 
 > Do you still need "tmp" ?  Perhaps you could further add the
 > following patch (untested, unbuilt, ...).
 > 
 > This saves copies and stack space for one cpumask (that's
 > 512 bits on my SN2 systems).
 > 
 > Signed-off-by: Paul Jackson <pj@sgi.com>
 > 
 > Index: 2.6.7-rc3-mm1/drivers/perfctr/virtual.c
 > ===================================================================
 > --- 2.6.7-rc3-mm1.orig/drivers/perfctr/virtual.c	2004-06-09 15:34:34.000000000 -0700
 > +++ 2.6.7-rc3-mm1/drivers/perfctr/virtual.c	2004-06-09 15:38:32.000000000 -0700
 > @@ -403,11 +403,10 @@
 >  		return -EFAULT;
 >  
 >  	if (control.cpu_control.nractrs || control.cpu_control.nrictrs) {
 > -		cpumask_t tmp, old_mask, new_mask;
 > +		cpumask_t old_mask, new_mask;
 >  
 > -		tmp = perfctr_cpus_forbidden_mask;
 >  		old_mask = tsk->cpus_allowed;
 > -		cpus_andnot(new_mask, old_mask, tmp);
 > +		cpus_andnot(new_mask, old_mask, perfctr_cpus_forbidden_mask);

Doesn't work because cpus_andnot() requires all three parameters
to be lvalues. In UP and PowerPC builds, perfctr_cpus_forbidden_mask
is #define:d to CPU_MASK_NONE to allow client-side optimisations.

Making it always be a variable will slow down UP and PowerPC with
unoptimisable cpumask tests; alternatively I'll have to wrap my
cpumask uses with optimisation macros and/or #ifdefs.

/Mikael

Re: [PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[Paul Jackson]

Mikael wrote:
>  > -		cpus_andnot(new_mask, old_mask, tmp);
>  > +		cpus_andnot(new_mask, old_mask, perfctr_cpus_forbidden_mask);
> 
> Doesn't work because cpus_andnot() requires all three parameters
> to be lvalues. ... CPU_MASK_NONE ...

I think your other fix (also done by Bill Irwin), make the above possible:

 #define CPU_MASK_NONE							\
-{ {									\
+((cpumask_t) { {							\


-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373

Re: [PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[William Lee Irwin III]

Mikael wrote:
>> Doesn't work because cpus_andnot() requires all three parameters
>> to be lvalues. ... CPU_MASK_NONE ...

On Thu, Jun 10, 2004 at 09:01:57AM -0700, Paul Jackson wrote:
> I think your other fix (also done by Bill Irwin), make the above possible:
>  #define CPU_MASK_NONE							\
> -{ {									\
> +((cpumask_t) { {							\

I've posted this at least twice, I think once in isolation for some
driver (MSI?) and once as part of the Alpha fixes.

Please get some cross-compilers together so we don't have every non-x86
arch exploding at once. Alpha vs. cpu_possible_map was horrendous.


-- wli

Re: [PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[Randy.Dunlap]

On Thu, 10 Jun 2004 09:03:50 -0700 William Lee Irwin III wrote:

| Mikael wrote:
| >> Doesn't work because cpus_andnot() requires all three parameters
| >> to be lvalues. ... CPU_MASK_NONE ...
| 
| On Thu, Jun 10, 2004 at 09:01:57AM -0700, Paul Jackson wrote:
| > I think your other fix (also done by Bill Irwin), make the above possible:
| >  #define CPU_MASK_NONE							\
| > -{ {									\
| > +((cpumask_t) { {							\
| 
| I've posted this at least twice, I think once in isolation for some
| driver (MSI?) and once as part of the Alpha fixes.
| 
| Please get some cross-compilers together so we don't have every non-x86
| arch exploding at once. Alpha vs. cpu_possible_map was horrendous.

or submit such patches to OSDL PLM.  PLM will apply the patch
(to whatever base you say, although you may have to supply the
"base" also; linus and -mm bases are already there)
and then try to cross-compile it on ia32, ia64, ppc32, ppc64, alpha,
sparc32, sparc64, and x86_64.

E.g., here's the results of 2.6.7-rc3-bk3:
https://www.osdl.org/plm-cgi/plm?module=patch_info&patch_id=3010

--
~Randy

Re: [PATCH][2.6.7-rc3-mm1] perfctr cpumask cleanup

[Paul Jackson]

William Lee Irwin wrote:
> Please get some cross-compilers together so we don't have every non-x86
> arch exploding at once.  Alpha vs. cpu_possible_map was horrendous.

Yes sir.

Randy Dunlap wrote:
> or submit such patches to OSDL PLM.

That too.

I'm reminded of the old saw:

  Fools rush in where angels fear to tread.

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373