1. 24 9月, 2009 28 次提交
  2. 23 9月, 2009 11 次提交
    • K
      walk system ram range · 908eedc6
      KAMEZAWA Hiroyuki 提交于
      Originally, walk_memory_resource() was introduced to traverse all memory
      of "System RAM" for detecting memory hotplug/unplug range.  For doing so,
      flags of IORESOUCE_MEM|IORESOURCE_BUSY was used and this was enough for
      memory hotplug.
      
      But for using other purpose, /proc/kcore, this may includes some firmware
      area marked as IORESOURCE_BUSY | IORESOUCE_MEM.  This patch makes the
      check strict to find out busy "System RAM".
      
      Note: PPC64 keeps their own walk_memory_resouce(), which walk through
      ppc64's lmb informaton.  Because old kclist_add() is called per lmb, this
      patch makes no difference in behavior, finally.
      
      And this patch removes CONFIG_MEMORY_HOTPLUG check from this function.
      Because pfn_valid() just show "there is memmap or not* and cannot be used
      for "there is physical memory or not", this function is useful in generic
      to scan physical memory range.
      Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: WANG Cong <xiyou.wangcong@gmail.com>
      Cc: Américo Wang <xiyou.wangcong@gmail.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Roland Dreier <rolandd@cisco.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      908eedc6
    • S
      procfs: provide stack information for threads · d899bf7b
      Stefani Seibold 提交于
      A patch to give a better overview of the userland application stack usage,
      especially for embedded linux.
      
      Currently you are only able to dump the main process/thread stack usage
      which is showed in /proc/pid/status by the "VmStk" Value.  But you get no
      information about the consumed stack memory of the the threads.
      
      There is an enhancement in the /proc/<pid>/{task/*,}/*maps and which marks
      the vm mapping where the thread stack pointer reside with "[thread stack
      xxxxxxxx]".  xxxxxxxx is the maximum size of stack.  This is a value
      information, because libpthread doesn't set the start of the stack to the
      top of the mapped area, depending of the pthread usage.
      
      A sample output of /proc/<pid>/task/<tid>/maps looks like:
      
      08048000-08049000 r-xp 00000000 03:00 8312       /opt/z
      08049000-0804a000 rw-p 00001000 03:00 8312       /opt/z
      0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
      a7d12000-a7d13000 ---p 00000000 00:00 0
      a7d13000-a7f13000 rw-p 00000000 00:00 0          [thread stack: 001ff4b4]
      a7f13000-a7f14000 ---p 00000000 00:00 0
      a7f14000-a7f36000 rw-p 00000000 00:00 0
      a7f36000-a8069000 r-xp 00000000 03:00 4222       /lib/libc.so.6
      a8069000-a806b000 r--p 00133000 03:00 4222       /lib/libc.so.6
      a806b000-a806c000 rw-p 00135000 03:00 4222       /lib/libc.so.6
      a806c000-a806f000 rw-p 00000000 00:00 0
      a806f000-a8083000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
      a8083000-a8084000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
      a8084000-a8085000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
      a8085000-a8088000 rw-p 00000000 00:00 0
      a8088000-a80a4000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
      a80a4000-a80a5000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
      a80a5000-a80a6000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
      afaf5000-afb0a000 rw-p 00000000 00:00 0          [stack]
      ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
      
      Also there is a new entry "stack usage" in /proc/<pid>/{task/*,}/status
      which will you give the current stack usage in kb.
      
      A sample output of /proc/self/status looks like:
      
      Name:	cat
      State:	R (running)
      Tgid:	507
      Pid:	507
      .
      .
      .
      CapBnd:	fffffffffffffeff
      voluntary_ctxt_switches:	0
      nonvoluntary_ctxt_switches:	0
      Stack usage:	12 kB
      
      I also fixed stack base address in /proc/<pid>/{task/*,}/stat to the base
      address of the associated thread stack and not the one of the main
      process.  This makes more sense.
      
      [akpm@linux-foundation.org: fs/proc/array.c now needs walk_page_range()]
      Signed-off-by: NStefani Seibold <stefani@seibold.net>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Alexey Dobriyan <adobriyan@gmail.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Randy Dunlap <randy.dunlap@oracle.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d899bf7b
    • M
      lockdep: use new arch_is_kernel_data() · 2a9ad18d
      Mike Frysinger 提交于
      This allows lockdep to locate symbols that are in arch-specific data
      sections (such as data in Blackfin on-chip SRAM regions).
      Signed-off-by: NMike Frysinger <vapier@gentoo.org>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Robin Getz <rgetz@blackfin.uclinux.org>
      Cc: Sam Ravnborg <sam@ravnborg.org>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2a9ad18d
    • M
      kallsyms: use new arch_is_kernel_text() · 128e8db3
      Mike Frysinger 提交于
      This allows kallsyms to locate symbols that are in arch-specific text
      sections (such as text in Blackfin on-chip SRAM regions).
      Signed-off-by: NMike Frysinger <vapier@gentoo.org>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Robin Getz <rgetz@blackfin.uclinux.org>
      Cc: Sam Ravnborg <sam@ravnborg.org>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      128e8db3
    • J
      getrusage: fill ru_maxrss value · 1f10206c
      Jiri Pirko 提交于
      Make ->ru_maxrss value in struct rusage filled accordingly to rss hiwater
      mark.  This struct is filled as a parameter to getrusage syscall.
      ->ru_maxrss value is set to KBs which is the way it is done in BSD
      systems.  /usr/bin/time (gnu time) application converts ->ru_maxrss to KBs
      which seems to be incorrect behavior.  Maintainer of this util was
      notified by me with the patch which corrects it and cc'ed.
      
      To make this happen we extend struct signal_struct by two fields.  The
      first one is ->maxrss which we use to store rss hiwater of the task.  The
      second one is ->cmaxrss which we use to store highest rss hiwater of all
      task childs.  These values are used in k_getrusage() to actually fill
      ->ru_maxrss.  k_getrusage() uses current rss hiwater value directly if mm
      struct exists.
      
      Note:
      exec() clear mm->hiwater_rss, but doesn't clear sig->maxrss.
      it is intetionally behavior. *BSD getrusage have exec() inheriting.
      
      test programs
      ========================================================
      
      getrusage.c
      ===========
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #include <sys/types.h>
       #include <sys/time.h>
       #include <sys/resource.h>
       #include <sys/types.h>
       #include <sys/wait.h>
       #include <unistd.h>
       #include <signal.h>
       #include <sys/mman.h>
      
       #include "common.h"
      
       #define err(str) perror(str), exit(1)
      
      int main(int argc, char** argv)
      {
      	int status;
      
      	printf("allocate 100MB\n");
      	consume(100);
      
      	printf("testcase1: fork inherit? \n");
      	printf("  expect: initial.self ~= child.self\n");
      	show_rusage("initial");
      	if (__fork()) {
      		wait(&status);
      	} else {
      		show_rusage("fork child");
      		_exit(0);
      	}
      	printf("\n");
      
      	printf("testcase2: fork inherit? (cont.) \n");
      	printf("  expect: initial.children ~= 100MB, but child.children = 0\n");
      	show_rusage("initial");
      	if (__fork()) {
      		wait(&status);
      	} else {
      		show_rusage("child");
      		_exit(0);
      	}
      	printf("\n");
      
      	printf("testcase3: fork + malloc \n");
      	printf("  expect: child.self ~= initial.self + 50MB\n");
      	show_rusage("initial");
      	if (__fork()) {
      		wait(&status);
      	} else {
      		printf("allocate +50MB\n");
      		consume(50);
      		show_rusage("fork child");
      		_exit(0);
      	}
      	printf("\n");
      
      	printf("testcase4: grandchild maxrss\n");
      	printf("  expect: post_wait.children ~= 300MB\n");
      	show_rusage("initial");
      	if (__fork()) {
      		wait(&status);
      		show_rusage("post_wait");
      	} else {
      		system("./child -n 0 -g 300");
      		_exit(0);
      	}
      	printf("\n");
      
      	printf("testcase5: zombie\n");
      	printf("  expect: pre_wait ~= initial, IOW the zombie process is not accounted.\n");
      	printf("          post_wait ~= 400MB, IOW wait() collect child's max_rss. \n");
      	show_rusage("initial");
      	if (__fork()) {
      		sleep(1); /* children become zombie */
      		show_rusage("pre_wait");
      		wait(&status);
      		show_rusage("post_wait");
      	} else {
      		system("./child -n 400");
      		_exit(0);
      	}
      	printf("\n");
      
      	printf("testcase6: SIG_IGN\n");
      	printf("  expect: initial ~= after_zombie (child's 500MB alloc should be ignored).\n");
      	show_rusage("initial");
      	signal(SIGCHLD, SIG_IGN);
      	if (__fork()) {
      		sleep(1); /* children become zombie */
      		show_rusage("after_zombie");
      	} else {
      		system("./child -n 500");
      		_exit(0);
      	}
      	printf("\n");
      	signal(SIGCHLD, SIG_DFL);
      
      	printf("testcase7: exec (without fork) \n");
      	printf("  expect: initial ~= exec \n");
      	show_rusage("initial");
      	execl("./child", "child", "-v", NULL);
      
      	return 0;
      }
      
      child.c
      =======
       #include <sys/types.h>
       #include <unistd.h>
       #include <sys/types.h>
       #include <sys/wait.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #include <sys/types.h>
       #include <sys/time.h>
       #include <sys/resource.h>
      
       #include "common.h"
      
      int main(int argc, char** argv)
      {
      	int status;
      	int c;
      	long consume_size = 0;
      	long grandchild_consume_size = 0;
      	int show = 0;
      
      	while ((c = getopt(argc, argv, "n:g:v")) != -1) {
      		switch (c) {
      		case 'n':
      			consume_size = atol(optarg);
      			break;
      		case 'v':
      			show = 1;
      			break;
      		case 'g':
      
      			grandchild_consume_size = atol(optarg);
      			break;
      		default:
      			break;
      		}
      	}
      
      	if (show)
      		show_rusage("exec");
      
      	if (consume_size) {
      		printf("child alloc %ldMB\n", consume_size);
      		consume(consume_size);
      	}
      
      	if (grandchild_consume_size) {
      		if (fork()) {
      			wait(&status);
      		} else {
      			printf("grandchild alloc %ldMB\n", grandchild_consume_size);
      			consume(grandchild_consume_size);
      
      			exit(0);
      		}
      	}
      
      	return 0;
      }
      
      common.c
      ========
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #include <sys/types.h>
       #include <sys/time.h>
       #include <sys/resource.h>
       #include <sys/types.h>
       #include <sys/wait.h>
       #include <unistd.h>
       #include <signal.h>
       #include <sys/mman.h>
      
       #include "common.h"
       #define err(str) perror(str), exit(1)
      
      void show_rusage(char *prefix)
      {
          	int err, err2;
          	struct rusage rusage_self;
          	struct rusage rusage_children;
      
          	printf("%s: ", prefix);
          	err = getrusage(RUSAGE_SELF, &rusage_self);
          	if (!err)
          		printf("self %ld ", rusage_self.ru_maxrss);
          	err2 = getrusage(RUSAGE_CHILDREN, &rusage_children);
          	if (!err2)
          		printf("children %ld ", rusage_children.ru_maxrss);
      
          	printf("\n");
      }
      
      /* Some buggy OS need this worthless CPU waste. */
      void make_pagefault(void)
      {
      	void *addr;
      	int size = getpagesize();
      	int i;
      
      	for (i=0; i<1000; i++) {
      		addr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
      		if (addr == MAP_FAILED)
      			err("make_pagefault");
      		memset(addr, 0, size);
      		munmap(addr, size);
      	}
      }
      
      void consume(int mega)
      {
          	size_t sz = mega * 1024 * 1024;
          	void *ptr;
      
          	ptr = malloc(sz);
          	memset(ptr, 0, sz);
      	make_pagefault();
      }
      
      pid_t __fork(void)
      {
      	pid_t pid;
      
      	pid = fork();
      	make_pagefault();
      
      	return pid;
      }
      
      common.h
      ========
      void show_rusage(char *prefix);
      void make_pagefault(void);
      void consume(int mega);
      pid_t __fork(void);
      
      FreeBSD result (expected result)
      ========================================================
      allocate 100MB
      testcase1: fork inherit?
        expect: initial.self ~= child.self
      initial: self 103492 children 0
      fork child: self 103540 children 0
      
      testcase2: fork inherit? (cont.)
        expect: initial.children ~= 100MB, but child.children = 0
      initial: self 103540 children 103540
      child: self 103564 children 0
      
      testcase3: fork + malloc
        expect: child.self ~= initial.self + 50MB
      initial: self 103564 children 103564
      allocate +50MB
      fork child: self 154860 children 0
      
      testcase4: grandchild maxrss
        expect: post_wait.children ~= 300MB
      initial: self 103564 children 154860
      grandchild alloc 300MB
      post_wait: self 103564 children 308720
      
      testcase5: zombie
        expect: pre_wait ~= initial, IOW the zombie process is not accounted.
                post_wait ~= 400MB, IOW wait() collect child's max_rss.
      initial: self 103564 children 308720
      child alloc 400MB
      pre_wait: self 103564 children 308720
      post_wait: self 103564 children 411312
      
      testcase6: SIG_IGN
        expect: initial ~= after_zombie (child's 500MB alloc should be ignored).
      initial: self 103564 children 411312
      child alloc 500MB
      after_zombie: self 103624 children 411312
      
      testcase7: exec (without fork)
        expect: initial ~= exec
      initial: self 103624 children 411312
      exec: self 103624 children 411312
      
      Linux result (actual test result)
      ========================================================
      allocate 100MB
      testcase1: fork inherit?
        expect: initial.self ~= child.self
      initial: self 102848 children 0
      fork child: self 102572 children 0
      
      testcase2: fork inherit? (cont.)
        expect: initial.children ~= 100MB, but child.children = 0
      initial: self 102876 children 102644
      child: self 102572 children 0
      
      testcase3: fork + malloc
        expect: child.self ~= initial.self + 50MB
      initial: self 102876 children 102644
      allocate +50MB
      fork child: self 153804 children 0
      
      testcase4: grandchild maxrss
        expect: post_wait.children ~= 300MB
      initial: self 102876 children 153864
      grandchild alloc 300MB
      post_wait: self 102876 children 307536
      
      testcase5: zombie
        expect: pre_wait ~= initial, IOW the zombie process is not accounted.
                post_wait ~= 400MB, IOW wait() collect child's max_rss.
      initial: self 102876 children 307536
      child alloc 400MB
      pre_wait: self 102876 children 307536
      post_wait: self 102876 children 410076
      
      testcase6: SIG_IGN
        expect: initial ~= after_zombie (child's 500MB alloc should be ignored).
      initial: self 102876 children 410076
      child alloc 500MB
      after_zombie: self 102880 children 410076
      
      testcase7: exec (without fork)
        expect: initial ~= exec
      initial: self 102880 children 410076
      exec: self 102880 children 410076
      Signed-off-by: NJiri Pirko <jpirko@redhat.com>
      Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
      Cc: Ingo Molnar <mingo@elte.hu>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1f10206c
    • S
      proc connector: add event for process becoming session leader · 02b51df1
      Scott James Remnant 提交于
      The act of a process becoming a session leader is a useful signal to a
      supervising init daemon such as Upstart.
      
      While a daemon will normally do this as part of the process of becoming a
      daemon, it is rare for its children to do so.  When the children do, it is
      nearly always a sign that the child should be considered detached from the
      parent and not supervised along with it.
      
      The poster-child example is OpenSSH; the per-login children call setsid()
      so that they may control the pty connected to them.  If the primary daemon
      dies or is restarted, we do not want to consider the per-login children
      and want to respawn the primary daemon without killing the children.
      
      This patch adds a new PROC_SID_EVENT and associated structure to the
      proc_event event_data union, it arranges for this to be emitted when the
      special PIDTYPE_SID pid is set.
      
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: NScott James Remnant <scott@ubuntu.com>
      Acked-by: NMatt Helsley <matthltc@us.ibm.com>
      Cc: Oleg Nesterov <oleg@tv-sign.ru>
      Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
      Acked-by: N"David S. Miller" <davem@davemloft.net>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      02b51df1
    • J
      seq_file: constify seq_operations · 88e9d34c
      James Morris 提交于
      Make all seq_operations structs const, to help mitigate against
      revectoring user-triggerable function pointers.
      
      This is derived from the grsecurity patch, although generated from scratch
      because it's simpler than extracting the changes from there.
      Signed-off-by: NJames Morris <jmorris@namei.org>
      Acked-by: NSerge Hallyn <serue@us.ibm.com>
      Acked-by: NCasey Schaufler <casey@schaufler-ca.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      88e9d34c
    • X
      generic-ipi: make struct call_function_data lockless · 54fdade1
      Xiao Guangrong 提交于
      This patch can remove spinlock from struct call_function_data, the
      reasons are below:
      
      1: add a new interface for cpumask named cpumask_test_and_clear_cpu(),
         it can atomically test and clear specific cpu, we can use it instead
         of cpumask_test_cpu() and cpumask_clear_cpu() and no need data->lock
         to protect those in generic_smp_call_function_interrupt().
      
      2: in smp_call_function_many(), after csd_lock() return, the current's
         cfd_data is deleted from call_function list, so it not have race
         between other cpus, then cfs_data is only used in
         smp_call_function_many() that must disable preemption and not from
         a hardware interrupthandler or from a bottom half handler to call,
         only the correspond cpu can use it, so it not have race in current
         cpu, no need cfs_data->lock to protect it.
      
      3: after 1 and 2, cfs_data->lock is only use to protect cfs_data->refs in
         generic_smp_call_function_interrupt(), so we can define cfs_data->refs
         to atomic_t, and no need cfs_data->lock any more.
      Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Jens Axboe <jens.axboe@oracle.com>
      Cc: Nick Piggin <nickpiggin@yahoo.com.au>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Acked-by: NRusty Russell <rusty@rustcorp.com.au>
      [akpm@linux-foundation.org: use atomic_dec_return()]
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      54fdade1
    • N
      kmod: fix race in usermodehelper code · c02e3f36
      Neil Horman 提交于
      The user mode helper code has a race in it.  call_usermodehelper_exec()
      takes an allocated subprocess_info structure, which it passes to a
      workqueue, and then passes it to a kernel thread which it creates, after
      which it calls complete to signal to the caller of
      call_usermodehelper_exec() that it can free the subprocess_info struct.
      
      But since we use that structure in the created thread, we can't call
      complete from __call_usermodehelper(), which is where we create the kernel
      thread.  We need to call complete() from within the kernel thread and then
      not use subprocess_info afterward in the case of UMH_WAIT_EXEC.  Tested
      successfully by me.
      Signed-off-by: NNeil Horman <nhorman@tuxdriver.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c02e3f36
    • D
      printk: add printk_delay to make messages readable for some scenarios · af91322e
      Dave Young 提交于
      When syslog is not possible, at the same time there's no serial/net
      console available, it will be hard to read the printk messages.  For
      example oops/panic/warning messages in shutdown phase.
      
      Add a printk delay feature, we can make each printk message delay some
      milliseconds.
      
      Setting the delay by proc/sysctl interface: /proc/sys/kernel/printk_delay
      
      The value range from 0 - 10000, default value is 0
      
      [akpm@linux-foundation.org: fix a few things]
      Signed-off-by: NDave Young <hidave.darkstar@gmail.com>
      Acked-by: NIngo Molnar <mingo@elte.hu>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      af91322e
    • D
      printk boot_delay: rename printk_delay_msec to loops_per_msec · 3a3b6ed2
      Dave Young 提交于
      Rename `printk_delay_msec' to `loops_per_msec', because the patch "printk:
      add printk_delay to make messages readable for some scenarios" wishes to
      more appropriately use the `printk_delay_msec' identifier.
      
      [akpm@linux-foundation.org: add a comment]
      Signed-off-by: NDave Young <hidave.darkstar@gmail.com>
      Acked-by: NIngo Molnar <mingo@elte.hu>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3a3b6ed2
  3. 22 9月, 2009 1 次提交
    • A
      cpuidle: fix the menu governor to boost IO performance · 69d25870
      Arjan van de Ven 提交于
      Fix the menu idle governor which balances power savings, energy efficiency
      and performance impact.
      
      The reason for a reworked governor is that there have been serious
      performance issues reported with the existing code on Nehalem server
      systems.
      
      To show this I'm sure Andrew wants to see benchmark results:
      (benchmark is "fio", "no cstates" is using "idle=poll")
      
      		no cstates	current linux	new algorithm
      1 disk		107 Mb/s	85 Mb/s		105 Mb/s
      2 disks		215 Mb/s	123 Mb/s	209 Mb/s
      12 disks	590 Mb/s	320 Mb/s	585 Mb/s
      
      In various power benchmark measurements, no degredation was found by our
      measurement&diagnostics team.  Obviously a small percentage more power was
      used in the "fio" benchmark, due to the much higher performance.
      
      While it would be a novel idea to describe the new algorithm in this
      commit message, I cheaped out and described it in comments in the code
      instead.
      
      [changes since first post: spelling fixes from akpm, review feedback,
      folded menu-tng into menu.c]
      Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
      Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
      Cc: Len Brown <lenb@kernel.org>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
      Acked-by: NIngo Molnar <mingo@elte.hu>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      69d25870