Linus Torvalds wrote: > > On Mon, 25 Aug 2008, Linus Torvalds wrote: >> But I'll look at your vmlinux, see what stands out. > > Oops. I already see the problem. > > Your .config has soem _huge_ CPU count, doesn't it? > > checkstack.pl shows these things as the top problems: > > 0xffffffff80266234 smp_call_function_mask [vmlinux]: 2736 > 0xffffffff80234747 __build_sched_domains [vmlinux]: 2232 > 0xffffffff8023523f __build_sched_domains [vmlinux]: 2232 > 0xffffffff8021e884 setup_IO_APIC_irq [vmlinux]: 1616 > 0xffffffff8021ee24 arch_setup_ht_irq [vmlinux]: 1600 > 0xffffffff8021f144 arch_setup_msi_irq [vmlinux]: 1600 > 0xffffffff8021e3b0 __assign_irq_vector [vmlinux]: 1592 > 0xffffffff8021e626 __assign_irq_vector [vmlinux]: 1592 > 0xffffffff8023257e move_task_off_dead_cpu [vmlinux]: 1592 > 0xffffffff802326e8 move_task_off_dead_cpu [vmlinux]: 1592 > 0xffffffff8025dbc5 tick_handle_oneshot_broadcast [vmlinux]:1544 > 0xffffffff8025dcb4 tick_handle_oneshot_broadcast [vmlinux]:1544 > 0xffffffff803f3dc4 store_scaling_governor [vmlinux]: 1376 > 0xffffffff80279ef4 cpuset_write_resmask [vmlinux]: 1360 > 0xffffffff803f465d cpufreq_add_dev [vmlinux]: 1352 > 0xffffffff803f495b cpufreq_add_dev [vmlinux]: 1352 > 0xffffffff803f3fc4 store_scaling_max_freq [vmlinux]: 1328 > 0xffffffff803f4064 store_scaling_min_freq [vmlinux]: 1328 > 0xffffffff803f44c4 cpufreq_update_policy [vmlinux]: 1328 > .. > > and sys_init_module is actually way way down the list. I bet the only > reason it showed up at all was because dynamically it was such a deep > callchain, and part of that callchain probably called some of those really > nasty things. > > Anyway, the reason smp_call_function_mask and friends have such _huge_ > stack usages for you is that they contain a 'cpumask_t' on the stack. > > For example, for me, usign a sane NR_CPU, the size of the stack frame for > smp_call_function_mask is under 200 bytes. For you, it's 2736 bytes. > > How about you make CONFIG_NR_CPU's something _sane_? Like 16? Or do you > really have four thousand CPU's in that system? > > Oh, I guess you have the MAXSMP config enabled? I really think that was a > bit too aggressive. > > Linus This probably all started when I was working on a software tool (aiod) that was failing because somebody ELSE had 4,096 CPUs configured. [[Seems that gcc had/has? it's MAX CPU value set to 1,024 (bits/sched.h __CPU_SETSIZE), so when you issue system calls like sched_getaffinity, it will "fail" for systems configured w/ 4,096 CPUs. I worked around it by simply forgetting about the gcc values, and kept allocating larger CPU masks until it worked.]] I think you're right: the kernel as a whole may not be ready for 4,096 CPUs apparently... Thanks for taking the time to look into this... Alan -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
