[10/23] SCHED: Only allocate per cpu cpu mask buffer with offstack cpumasks
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From: Andi Kleen on 10 Jun 2010 11:10 Peter Zijlstra <peterz(a)infradead.org> writes: > On Thu, 2010-06-10 at 16:52 +0200, Andi Kleen wrote: >> > This patch will actually break things.. please read the code. >> > >> > I guess we could move the unsigned long into that block, but I really >> > don't see the point. >> >> How does it break things? >> >> ptr is not used for anything unless that define is set. gcc doesn't >> lie on this. Ok. For the !FAIR_GROUP_SCHED || !CPUMASK_OFFSTACK case it's still wasted memory because it is not used for anything. If you enable the kmemleak tracer you should also get a warning about this I updated the patch with a better ifdef to have CONFIG_UNFAIR_GROUP_SCHED too. -Andi --- SCHED: Only allocate per cpu cpu mask buffer with offstack cpumasks v2 This will save a few bytes in the non offstack cpumask case. Found by gcc 4.6's new warnings. Cc: peterz(a)infradead.org Cc: mingo(a)elte.hu Signed-off-by: Andi Kleen <ak(a)linux.intel.com> --- kernel/sched.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) Index: linux-2.6.35-rc2-gcc/kernel/sched.c =================================================================== --- linux-2.6.35-rc2-gcc.orig/kernel/sched.c +++ linux-2.6.35-rc2-gcc/kernel/sched.c @@ -7482,7 +7482,7 @@ static void init_tg_rt_entry(struct task void __init sched_init(void) { int i, j; - unsigned long alloc_size = 0, ptr; + unsigned long alloc_size = 0; #ifdef CONFIG_FAIR_GROUP_SCHED alloc_size += 2 * nr_cpu_ids * sizeof(void **); @@ -7494,7 +7494,10 @@ void __init sched_init(void) alloc_size += num_possible_cpus() * cpumask_size(); #endif if (alloc_size) { +#if defined(CONFIG_CPUMASK_OFFSTACK) || defined(CONFIG_FAIR_GROUP_SCHED) + unsigned long ptr; ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT); +#endif #ifdef CONFIG_FAIR_GROUP_SCHED init_task_group.se = (struct sched_entity **)ptr; -- ak(a)linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |