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Date: Wed, 22 Dec 2010 16:27:32 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: shaohui.zheng@...el.com
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
haicheng.li@...ux.intel.com, lethal@...ux-sh.org,
ak@...ux.intel.com, shaohui.zheng@...ux.intel.com,
rientjes@...gle.com, dave@...ux.vnet.ibm.com, gregkh@...e.de,
Sam Ravnborg <sam@...nborg.org>,
Haicheng Li <haicheng.li@...el.com>
Subject: Re: [6/7, v9] NUMA Hotplug Emulator: Fake CPU socket with logical
CPU on x86
On Fri, 10 Dec 2010 15:31:25 +0800
shaohui.zheng@...el.com wrote:
> From: Shaohui Zheng <shaohui.zheng@...el.com>
>
> When hotplug a CPU with emulator, we are using a logical CPU to emulate the
> CPU hotplug process. For the CPU supported SMT, some logical CPUs are in the
> same socket, but it may located in different NUMA node after we have emulator.
> it misleads the scheduling domain to build the incorrect hierarchy, and it
> causes the following call trace when rebalance the scheduling domain:
>
> divide error: 0000 [#1] SMP
> last sysfs file: /sys/devices/system/cpu/cpu8/online
> CPU 0
> Modules linked in: fbcon tileblit font bitblit softcursor radeon ttm drm_kms_helper e1000e usbhid via_rhine mii drm i2c_algo_bit igb dca
> Pid: 0, comm: swapper Not tainted 2.6.32hpe #78 X8DTN
> RIP: 0010:[<ffffffff81051da5>] [<ffffffff81051da5>] find_busiest_group+0x6c5/0xa10
> RSP: 0018:ffff880028203c30 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000015ac0 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffff880277e8cfa0 RDI: 0000000000000000
> RBP: ffff880028203dc0 R08: ffff880277e8cfa0 R09: 0000000000000040
> R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> FS: 0000000000000000(0000) GS:ffff880028200000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> CR2: 00007f16cfc85770 CR3: 0000000001001000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process swapper (pid: 0, threadinfo ffffffff81822000, task ffffffff8184a600)
> Stack:
> ffff880028203d60 ffff880028203cd0 ffff8801c204ff08 ffff880028203e38
> <0> 0101ffff81018c59 ffff880028203e44 00000001810806bd ffff8801c204fe00
> <0> 0000000528200000 ffffffff00000000 0000000000000018 0000000000015ac0
> Call Trace:
> <IRQ>
> [<ffffffff81088ee0>] ? tick_dev_program_event+0x40/0xd0
> [<ffffffff81053b2c>] rebalance_domains+0x17c/0x570
> [<ffffffff81018c89>] ? read_tsc+0x9/0x20
> [<ffffffff81088ee0>] ? tick_dev_program_event+0x40/0xd0
> [<ffffffff810569ed>] run_rebalance_domains+0xbd/0xf0
> [<ffffffff8106471f>] __do_softirq+0xaf/0x1e0
> [<ffffffff810b7d18>] ? handle_IRQ_event+0x58/0x160
> [<ffffffff810130ac>] call_softirq+0x1c/0x30
> [<ffffffff81014a85>] do_softirq+0x65/0xa0
> [<ffffffff810645cd>] irq_exit+0x7d/0x90
> [<ffffffff81013ff0>] do_IRQ+0x70/0xe0
> [<ffffffff810128d3>] ret_from_intr+0x0/0x11
> <EOI>
> [<ffffffff8133387f>] ? acpi_idle_enter_bm+0x281/0x2b5
> [<ffffffff81333878>] ? acpi_idle_enter_bm+0x27a/0x2b5
> [<ffffffff8145dc8f>] ? cpuidle_idle_call+0x9f/0x130
> [<ffffffff81010e2b>] ? cpu_idle+0xab/0x100
> [<ffffffff8158aee6>] ? rest_init+0x66/0x70
> [<ffffffff81905d90>] ? start_kernel+0x3e3/0x3ef
> [<ffffffff8190533a>] ? x86_64_start_reservations+0x125/0x129
> [<ffffffff81905438>] ? x86_64_start_kernel+0xfa/0x109
> Code: 00 00 e9 4c fb ff ff 0f 1f 80 00 00 00 00 48 8b b5 d8 fe ff ff 48 8b 45 a8 4d 29 ef 8b 56 08 48 c1 e0 0a 49 89 f0 48 89 d7 31 d2 <48> f7 f7 31 d2 48 89 45 a0 8b 76 08 4c 89 f0 48 c1 e0 0a 48 f7
> RIP [<ffffffff81051da5>] find_busiest_group+0x6c5/0xa10
> RSP <ffff880028203c30>
>
> Solution:
>
> We put the logical CPU into a fake CPU socket, and assign it an unique
> phys_proc_id. For the fake socket, we put one logical CPU in only. This
> method fixes the above bug.
>
>
> ...
>
> --- linux-hpe4.orig/arch/x86/include/asm/processor.h 2010-11-17 09:00:51.354100239 +0800
> +++ linux-hpe4/arch/x86/include/asm/processor.h 2010-11-17 09:01:10.222837594 +0800
> @@ -113,6 +113,15 @@
> /* Index into per_cpu list: */
> u16 cpu_index;
> #endif
> +
> +#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
> + /*
> + * Use a logic cpu to emulate a physical cpu's hotplug. We put the
"logical".
> + * logical cpu into a fake socket, assign a fake physical id to it,
> + * and create a fake core.
> + */
> + __u8 cpu_probe_on; /* A flag to enable cpu probe/release */
> +#endif
> } __attribute__((__aligned__(SMP_CACHE_BYTES)));
>
> #define X86_VENDOR_INTEL 0
> Index: linux-hpe4/arch/x86/kernel/smpboot.c
> ===================================================================
> --- linux-hpe4.orig/arch/x86/kernel/smpboot.c 2010-11-17 09:01:10.202837209 +0800
> +++ linux-hpe4/arch/x86/kernel/smpboot.c 2010-11-17 09:01:10.222837594 +0800
> @@ -97,6 +97,7 @@
> */
> static DEFINE_MUTEX(x86_cpu_hotplug_driver_mutex);
>
> +#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
> void cpu_hotplug_driver_lock()
> {
> mutex_lock(&x86_cpu_hotplug_driver_mutex);
> @@ -106,6 +107,7 @@
> {
> mutex_unlock(&x86_cpu_hotplug_driver_mutex);
> }
> +#endif
>
> #else
> static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
> @@ -198,6 +200,8 @@
> {
> int cpuid, phys_id;
> unsigned long timeout;
> + u8 cpu_probe_on = 0;
Unneeded initialisation.
Does this cause an unused var warning when
CONFIG_ARCH_CPU_PROBE_RELEASE=n?
> + struct cpuinfo_x86 *c;
>
> /*
> * If waken up by an INIT in an 82489DX configuration
>
> ...
>
> +#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
> +/*
> + * Put the logical cpu into a new sokect, and encapsule it into core 0.
That comment needs help.
> + */
> +static void fake_cpu_socket_info(int cpu)
> +{
> + struct cpuinfo_x86 *c = &cpu_data(cpu);
> + int i, phys_id = 0;
> +
> + /* calculate the max phys_id */
> + for_each_present_cpu(i) {
> + struct cpuinfo_x86 *c = &cpu_data(i);
> + if (phys_id < c->phys_proc_id)
> + phys_id = c->phys_proc_id;
> + }
> +
> + c->phys_proc_id = phys_id + 1; /* pick up a unused phys_proc_id */
> + c->cpu_core_id = 0; /* always put the logical cpu to core 0 */
> + c->cpu_probe_on = 1;
> +}
> +
>
> ...
>
--
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