Messages in this thread Patch in this message | | | Date | Fri, 17 Jan 2003 05:08:03 -0500 (EST) | From | Zwane Mwaikambo <> | Subject | Re: [PATCH][2.5] per-CPU task runqueues |
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On Fri, 17 Jan 2003, Andrew Morton wrote:
> Zwane Mwaikambo <zwane@holomorphy.com> wrote: > > > > This patch simply switches over to per-CPU runqueues as defined by the new > > per cpu api. > > ... > > +static DEFINE_PER_CPU(struct runqueue, runqueues); > > These must be initialised to something. gcc-2.91/92 bug. There is a > build-time check for this, but it only detects the mistake if you're using a > compiler which has the bug.
Thanks i can work around that.
> Your patch works here, but I was never able to get this working when the > per-cpu areas were allocated as the CPU's come online, which is something we > kinda should work towards. This patch would need to be reverted if we try to > do that again. Which is a shame, because appreciable amounts of memory would > be saved if nr_cpus < NR_CPUS. scheduler startup is fragile..
I think i'll have a stab at that.
> I don't think it buys us a lot, really. These structures are so humongous > that we don't get much per-cpuness in accessing them.
Point.
Index: linux-2.5.59/kernel/sched.c =================================================================== RCS file: /build/cvsroot/linux-2.5.59/kernel/sched.c,v retrieving revision 1.1.1.1 diff -u -r1.1.1.1 sched.c --- linux-2.5.59/kernel/sched.c 17 Jan 2003 02:46:29 -0000 1.1.1.1 +++ linux-2.5.59/kernel/sched.c 17 Jan 2003 10:03:31 -0000 @@ -160,9 +160,9 @@ atomic_t nr_iowait; } ____cacheline_aligned; -static struct runqueue runqueues[NR_CPUS] __cacheline_aligned; +static DEFINE_PER_CPU(struct runqueue, runqueues) = {{ 0 }}; -#define cpu_rq(cpu) (runqueues + (cpu)) +#define cpu_rq(cpu) (&per_cpu(runqueues, cpu)) #define this_rq() cpu_rq(smp_processor_id()) #define task_rq(p) cpu_rq(task_cpu(p)) #define cpu_curr(cpu) (cpu_rq(cpu)->curr) -- function.linuxpower.ca
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