[PATCH v2] xen: sched: removal of redundant check in Credit

[PATCH v2] xen: sched: removal of redundant check in Credit

[Praveen Kumar]

The patch gets rid of a redundant check in csched_vcpu_acct. In fact,
the function is only called from csched_tick, which already checks
that current is not the idle vcpu. The patch also adds an ASSERT to
the same effect, in order to make assumption ( i.e., no calling this
on idle vcpus) even more clear and as a guard for future mis-use.

Signed-off-by: Praveen Kumar <kpraveen.lkml@gmail.com>

---
Changed since v1:
   * Changelog updated as per the comment.

v2:

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index fc3a321..dfe8545 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -941,6 +941,7 @@ csched_vcpu_acct(struct csched_private *prv,
unsigned int cpu)

     ASSERT( current->processor == cpu );
     ASSERT( svc->sdom != NULL );
+    ASSERT( !is_idle_vcpu(svc->vcpu) );

     /*
      * If this VCPU's priority was boosted when it last awoke, reset
it.
@@ -957,8 +958,7 @@ csched_vcpu_acct(struct csched_private *prv,
unsigned int cpu)
     /*
      * Update credits
      */
-    if ( !is_idle_vcpu(svc->vcpu) )
-        burn_credits(svc, NOW());
+    burn_credits(svc, NOW());

     /*
      * Put this VCPU and domain back on the active list if it was

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Re: [PATCH v2] xen: sched: removal of redundant check in Credit

[Dario Faggioli]

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On Thu, 2016-12-15 at 23:39 +0530, Praveen Kumar wrote:
> The patch gets rid of a redundant check in csched_vcpu_acct. In fact,
> the function is only called from csched_tick, which already checks
> that current is not the idle vcpu. The patch also adds an ASSERT to
> the same effect, in order to make assumption ( i.e., no calling this
> on idle vcpus) even more clear and as a guard for future mis-use.
> 
> Signed-off-by: Praveen Kumar <kpraveen.lkml@gmail.com>
> 
This is all good and can have my:

Acked-by: Dario Faggioli <dario.faggioli@citrix.com>

_HOWEVER_ when I tried to apply the patch directly from this email I
get this:

(Stripping trailing CRs from patch; use --binary to disable.)
checking file xen/common/sched_credit.c
patch: **** malformed patch at line 6: unsigned int cpu)

Which I think means that the patch has been corrupted, most likely by
the email program.

This is a common issue, and although it is possible to paste patches in
an email client and teach it not to mangle them, I would say:
 1) it's a very boring thing to do, it does not scale, it's not
    practical when sending patch series and it's not reliable;
 2) I've only done a couple of times at the beginning of my OS 
    contribution history, and would not be able to help on how to make 
    that happen.

For this reason, I encourage you to look at and learn alternative ways 
of submitting patches, like git-send-email. Personally, I use StGit for
development, and it has its own sending patches machinery too.

I think you should send a v3, by using one of these methods (or, in
general, not in a mangled state). When doing that (and if you don't
change anything), you can stick my 'Acked-by:' tag right below your own
'Signed-off-by:'

Thanks and Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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