Messages in this thread Patch in this message |  | | | Date | Sat, 20 Dec 2008 10:06:38 +0530 | | From | Vaidyanathan Srinivasan <> | | Subject | Re: [PATCH v7 4/8] sched: nominate preferred wakeup cpu |
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* Andrew Morton <akpm@linux-foundation.org> [2008-12-19 13:55:08]:
> On Thu, 18 Dec 2008 23:26:22 +0530 > Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> wrote: > > > When the system utilisation is low and more cpus are idle, > > then the process waking up from sleep should prefer to > > wakeup an idle cpu from semi-idle cpu package (multi core > > package) rather than a completely idle cpu package which > > would waste power. > > > > Use the sched_mc balance logic in find_busiest_group() to > > nominate a preferred wakeup cpu. > > > > This info can be sored in appropriate sched_domain, but > > updating this info in all copies of sched_domain is not > > practical. Hence this information is stored in root_domain > > struct which is one copy per partitioned sched domain. > > The root_domain can be accessed from each cpu's runqueue > > and there is one copy per partitioned sched domain. > > > > kernel/sched.c: In function 'find_busiest_group': > kernel/sched.c:3403: warning: passing argument 1 of '__first_cpu' from incompatible pointer type > > Due to > > first_cpu(group_leader->cpumask); > > apparently because Rusty changed sched_group.cpumask into a plain old > array and nobody tests their stuff against the tree into which it is > actually integrated :(
Hi Andrew,
I agree. These are integration issues and I will test better next time.
There were two such bugs which Ingo fixed in the tip.
commit 220e7f617826e0527bbc523ba859f6a4bae0bfe1 Author: Ingo Molnar <mingo@elte.hu> Date: Fri Dec 19 00:53:40 2008 +0100
sched: fix warning in kernel/sched.c
Impact: fix cpumask conversion bug
this warning:
kernel/sched.c: In function find_busiest_group: kernel/sched.c:3429: warning: passing argument 1 of __first_cpu from incompatible pointer type
shows that we forgot to convert a new patch to the new cpumask APIs.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
commit edb4c71953409c1deac1a80528ac0aa768762b33 Author: Ingo Molnar <mingo@elte.hu> Date: Thu Dec 18 21:30:23 2008 +0100
sched: move test_sd_parent() to an SMP section of sched.h
Impact: build fix
Signed-off-by: Ingo Molnar <mingo@elte.hu>
I have tested the sched-tip with these fixes.
> > kernel/sched.c: In function 'schedule': > kernel/sched.c:3679: warning: 'active_balance' may be used uninitialized in this function > > This warning is correct - the code is buggy.
Yes this is my code bug. I did not see the warning in sched.c. Is there any build option that I need to pass in order to get -Wall effect?
Here is the fix to initialise the active_balance=0.
Thanks for the detailed review. I will work to improve the quality of my submission.
--Vaidy
sched: bug fix -- initialise active_balance variable
In sched.c load_balance_newidle, potential use of uninitialised variable.
Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
diff --git a/kernel/sched.c b/kernel/sched.c index e6a88bf..a21fe6d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3692,7 +3692,7 @@ redo: } if (!ld_moved) { - int active_balance; + int active_balance = 0; schedstat_inc(sd, lb_failed[CPU_NEWLY_IDLE]); if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
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