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Message-ID: <AANLkTikZiRw2w9hveCxA2XQp8SYs-4rYpH4BdZOns2CS@mail.gmail.com>
Date: Sat, 15 May 2010 18:47:00 +0530
From: Jaswinder Singh Rajput <jaswinderlinux@...il.com>
To: akpm@...ux-foundation.org, linux-mm@...ck.org,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Yinghai Lu <yinghai@...nel.org>,
David Rientjes <rientjes@...gle.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Mel Gorman <mel@....ul.ie>,
Lee Schermerhorn <lee.schermerhorn@...com>,
linux-kernel@...r.kernel.org, ak@...ux.intel.co,
fengguang.wu@...el.com, haicheng.li@...ux.intel.com,
shaohui.zheng@...ux.intel.com
Subject: Re: [RFC,2/7] NUMA Hotplug emulator
Hello,
On Thu, May 13, 2010 at 5:15 PM, Shaohui Zheng <shaohui.zheng@...el.com> wrote:
> x86: infrastructure of NUMA hotplug emulation
>
> NUMA hotplug emulator introduces a new node state N_HIDDEN to
> identify the fake offlined node. It firstly hides RAM via E820
> table and then emulates fake offlined nodes with the hidden RAM.
>
> After system bootup, user is able to hotplug-add these offlined
> nodes, which is just similar to a real hardware hotplug behavior.
>
> Using boot option "numa=hide=N*size" to fake offlined nodes:
> - N is the number of hidden nodes
> - size is the memory size (in MB) per hidden node.
>
> OPEN: Kernel might use part of hidden memory region as RAM buffer,
> now emulator directly hide 128M extra space to workaround
> this issue. Any better way to avoid this conflict?
>
> Signed-off-by: Haicheng Li <haicheng.li@...ux.intel.com>
> Signed-off-by: Shaohui Zheng <shaohui.zheng@...el.com>
> ---
> diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
> index 8948f47..3e0d94d 100644
> --- a/arch/x86/mm/numa_64.c
> +++ b/arch/x86/mm/numa_64.c
> @@ -307,6 +307,87 @@ void __init numa_init_array(void)
> }
> }
>
> +#ifdef CONFIG_NODE_HOTPLUG_EMU
> +static char *hp_cmdline __initdata;
> +static struct bootnode *hidden_nodes;
> +static u64 hp_start, hp_end;
> +static long hidden_num, hp_size;
> +
> +int hotadd_hidden_nodes(int nid)
> +{
> + int ret;
> +
> + if (!node_hidden(nid))
> + return -EINVAL;
> +
> + ret = add_memory(nid, hidden_nodes[nid].start,
> + hidden_nodes[nid].end - hidden_nodes[nid].start);
> + if (!ret) {
> + node_clear_hidden(nid);
> + return 0;
> + } else {
> + return -EEXIST;
> + }
> +}
> +
> +static void __init numa_hide_nodes(void)
> +{
> + char *c;
> + int ret;
> +
> + c = strchr(hp_cmdline, '*');
> + if (!c)
> + return;
> + else
> + *c = '\0';
> + ret = strict_strtol(hp_cmdline, 0, &hidden_num);
> + if (ret == -EINVAL)
> + return;
> + ret = strict_strtol(c + 1, 0, &hp_size);
> + if (ret == -EINVAL)
> + return;
> + hp_size <<= 20;
> +
> + hp_start = e820_hide_mem(hidden_num * hp_size);
> + if (hp_start <= 0) {
> + printk(KERN_ERR "Hide too much memory, disable node hotplug emualtion.");
> + hidden_num = 0;
> + return;
> + }
> +
> + hp_end = hp_start + hidden_num * hp_size;
> +
> + /* leave 128M space for possible RAM buffer usage later
> + * any other better way to avoid this conflict?
> + */
> + e820_hide_mem(128*1024*1024);
> +}
> +
> +static void __init numa_hotplug_emulation(void)
> +{
> + int i, num_nodes = 0;
> +
> + for_each_online_node(i)
> + if (i > num_nodes)
> + num_nodes = i;
> +
> + i = num_nodes + hidden_num;
> + if (!hidden_nodes) {
> + hidden_nodes = alloc_bootmem(sizeof(struct bootnode) * i);
> + memset(hidden_nodes, 0, sizeof(struct bootnode) * i);
> + }
> +
> + if (hidden_num)
if (hidden_num) is not required, as next line's for statement is also
doing the same thing.
Thanks,
--
Jaswinder Singh.
> + for (i = 0; i < hidden_num; i++) {
> + int nid = num_nodes + i + 1;
> + node_set(nid, node_possible_map);
> + hidden_nodes[nid].start = hp_start + hp_size * i;
> + hidden_nodes[nid].end = hp_start + hp_size * (i+1);
> + node_set_hidden(nid);
> + }
> +}
> +#endif /* CONFIG_NODE_HOTPLUG_EMU */
> +
> #ifdef CONFIG_NUMA_EMU
> /* Numa emulation */
> static struct bootnode nodes[MAX_NUMNODES] __initdata;
> @@ -661,7 +742,7 @@ void __init initmem_init(unsigned long start_pfn, unsigned long last_pfn,
>
> #ifdef CONFIG_NUMA_EMU
> if (cmdline && !numa_emulation(start_pfn, last_pfn, acpi, k8))
> - return;
> + goto done;
> nodes_clear(node_possible_map);
> nodes_clear(node_online_map);
> #endif
> @@ -669,14 +750,14 @@ void __init initmem_init(unsigned long start_pfn, unsigned long last_pfn,
> #ifdef CONFIG_ACPI_NUMA
> if (!numa_off && acpi && !acpi_scan_nodes(start_pfn << PAGE_SHIFT,
> last_pfn << PAGE_SHIFT))
> - return;
> + goto done;
> nodes_clear(node_possible_map);
> nodes_clear(node_online_map);
> #endif
>
> #ifdef CONFIG_K8_NUMA
> if (!numa_off && k8 && !k8_scan_nodes())
> - return;
> + goto done;
> nodes_clear(node_possible_map);
> nodes_clear(node_online_map);
> #endif
> @@ -696,6 +777,12 @@ void __init initmem_init(unsigned long start_pfn, unsigned long last_pfn,
> numa_set_node(i, 0);
> e820_register_active_regions(0, start_pfn, last_pfn);
> setup_node_bootmem(0, start_pfn << PAGE_SHIFT, last_pfn << PAGE_SHIFT);
> +done:
> +#ifdef CONFIG_NODE_HOTPLUG_EMU
> + if (hidden_num)
> + numa_hotplug_emulation();
> +#endif
> + return;
> }
>
> unsigned long __init numa_free_all_bootmem(void)
> @@ -723,6 +810,12 @@ static __init int numa_setup(char *opt)
> if (!strncmp(opt, "fake=", 5))
> cmdline = opt + 5;
> #endif
> +#ifdef CONFIG_NODE_HOTPLUG_EMU
> + if (!strncmp(opt, "hide=", 5)) {
> + hp_cmdline = opt + 5;
> + numa_hide_nodes();
> + }
> +#endif
> #ifdef CONFIG_ACPI_NUMA
> if (!strncmp(opt, "noacpi", 6))
> acpi_numa = -1;
> diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> index dba35e4..ba0f82d 100644
> --- a/include/linux/nodemask.h
> +++ b/include/linux/nodemask.h
> @@ -371,6 +371,10 @@ static inline void __nodes_fold(nodemask_t *dstp, const nodemask_t *origp,
> */
> enum node_states {
> N_POSSIBLE, /* The node could become online at some point */
> +#ifdef CONFIG_NODE_HOTPLUG_EMU
> + N_HIDDEN, /* The node is hidden at booting time, could be
> + * onlined in run time */
> +#endif
> N_ONLINE, /* The node is online */
> N_NORMAL_MEMORY, /* The node has regular memory */
> #ifdef CONFIG_HIGHMEM
> @@ -470,6 +474,13 @@ static inline int num_node_state(enum node_states state)
> #define node_online(node) node_state((node), N_ONLINE)
> #define node_possible(node) node_state((node), N_POSSIBLE)
>
> +#ifdef CONFIG_NODE_HOTPLUG_EMU
> +#define node_set_hidden(node) node_set_state((node), N_HIDDEN)
> +#define node_clear_hidden(node) node_clear_state((node), N_HIDDEN)
> +#define node_hidden(node) node_state((node), N_HIDDEN)
> +extern int hotadd_hidden_nodes(int nid);
> +#endif
> +
> #define for_each_node(node) for_each_node_state(node, N_POSSIBLE)
> #define for_each_online_node(node) for_each_node_state(node, N_ONLINE)
>
> --
> Thanks & Regards,
> Shaohui
>
>
--
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