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    Contents of /trunk/kernel26-alx/patches-2.6.20-r6/0003-2.6.20-sched-staircase17_compute_tunable.patch

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    Revision 1175 - (show annotations) (download)
    Thu Oct 14 12:15:46 2010 UTC (13 years, 6 months ago) by niro
    File size: 6142 byte(s) 
    -2.6.20-alx-r6 new magellan 0.5.2 kernel
    1 Add the compute tunable for the staircase cpu scheduler. This modifies the
    2 cpu scheduler behaviour for significantly longer cpu timeslices and delays
    3 normal preemption to minimise the cpu cache harming effects of multiple
    4 concurrent running tasks. This increases cpu throughput at the cost of
    5 significantly increased latencies.
    6
    7 Signed-off-by: Con Kolivas <kernel@kolivas.org>
    8
    9 Documentation/sysctl/kernel.txt | 11 ++++++++++
    10 include/linux/sched.h | 2 -
    11 kernel/sched.c | 41 +++++++++++++++++++++++++++++++---------
    12 kernel/sysctl.c | 8 +++++++
    13 4 files changed, 52 insertions(+), 10 deletions(-)
    14
    15 Index: linux-2.6.20-ck1/include/linux/sched.h
    16 ===================================================================
    17 --- linux-2.6.20-ck1.orig/include/linux/sched.h 2007-02-16 19:01:30.000000000 +1100
    18 +++ linux-2.6.20-ck1/include/linux/sched.h 2007-02-16 19:01:30.000000000 +1100
    19 @@ -216,7 +216,7 @@ extern void show_stack(struct task_struc
    20
    21 void io_schedule(void);
    22 long io_schedule_timeout(long timeout);
    23 -extern int sched_interactive;
    24 +extern int sched_interactive, sched_compute;
    25
    26 extern void cpu_init (void);
    27 extern void trap_init(void);
    28 Index: linux-2.6.20-ck1/kernel/sched.c
    29 ===================================================================
    30 --- linux-2.6.20-ck1.orig/kernel/sched.c 2007-02-16 19:01:30.000000000 +1100
    31 +++ linux-2.6.20-ck1/kernel/sched.c 2007-02-16 19:01:30.000000000 +1100
    32 @@ -63,8 +63,17 @@
    33 /*
    34 * sched_interactive - sysctl which allows interactive tasks to have bonus
    35 * raise its priority.
    36 + * sched_compute - sysctl which enables long timeslices and delayed preemption
    37 + * for compute server usage.
    38 */
    39 int sched_interactive __read_mostly = 1;
    40 +int sched_compute __read_mostly;
    41 +
    42 +/*
    43 + * CACHE_DELAY is the time preemption is delayed in sched_compute mode
    44 + * and is set to a nominal 10ms.
    45 + */
    46 +#define CACHE_DELAY (10 * (HZ) / 1001 + 1)
    47
    48 /*
    49 * Convert user-nice values [ -20 ... 0 ... 19 ]
    50 @@ -96,9 +105,10 @@ int sched_interactive __read_mostly = 1;
    51
    52 /*
    53 * This is the time all tasks within the same priority round robin.
    54 - * Set to a minimum of 6ms.
    55 + * Set to a minimum of 6ms. It is 10 times longer in compute mode.
    56 */
    57 -#define RR_INTERVAL ((6 * HZ / 1001) + 1)
    58 +#define _RR_INTERVAL ((6 * HZ / 1001) + 1)
    59 +#define RR_INTERVAL (_RR_INTERVAL * (1 + 9 * sched_compute))
    60 #define DEF_TIMESLICE (RR_INTERVAL * 19)
    61
    62 /*
    63 @@ -132,6 +142,7 @@ struct rq {
    64
    65 /* Cached timestamp set by update_cpu_clock() */
    66 unsigned long long most_recent_timestamp;
    67 + unsigned short cache_ticks, preempted;
    68 struct task_struct *curr, *idle;
    69 unsigned long next_balance;
    70 struct mm_struct *prev_mm;
    71 @@ -873,7 +884,7 @@ static inline int __normal_prio(struct t
    72
    73 best_bonus = bonus(p);
    74 prio = MAX_RT_PRIO + best_bonus;
    75 - if (sched_interactive && !batch_task(p))
    76 + if (sched_interactive && !sched_compute && !batch_task(p))
    77 prio -= p->bonus;
    78
    79 rr = rr_interval(p);
    80 @@ -1347,14 +1358,22 @@ static inline int wake_idle(int cpu, str
    81 #endif
    82
    83 /*
    84 - * Check to see if p preempts rq->curr and resched if it does.
    85 + * Check to see if p preempts rq->curr and resched if it does. In compute
    86 + * mode we do not preempt for at least CACHE_DELAY and set rq->preempted.
    87 */
    88 -static inline void preempt(const struct task_struct *p, struct rq *rq)
    89 +static void fastcall preempt(const struct task_struct *p, struct rq *rq)
    90 {
    91 - if (TASK_PREEMPTS_CURR(p, rq))
    92 - resched_task(rq->curr);
    93 -}
    94 + struct task_struct *curr = rq->curr;
    95
    96 + if (p->prio >= curr->prio)
    97 + return;
    98 + if (!sched_compute || rq->cache_ticks >= CACHE_DELAY || !p->mm ||
    99 + rt_task(p) || curr == rq->idle) {
    100 + resched_task(curr);
    101 + return;
    102 + }
    103 + rq->preempted = 1;
    104 +}
    105
    106 /***
    107 * try_to_wake_up - wake up a thread
    108 @@ -3008,6 +3027,9 @@ static void task_running_tick(struct rq
    109 time_slice_expired(p, rq);
    110 goto out_unlock;
    111 }
    112 + rq->cache_ticks++;
    113 + if (rq->preempted && rq->cache_ticks >= CACHE_DELAY)
    114 + set_tsk_need_resched(p);
    115 out_unlock:
    116 spin_unlock(&rq->lock);
    117 }
    118 @@ -3304,6 +3326,7 @@ switch_tasks:
    119
    120 sched_info_switch(prev, next);
    121 if (likely(prev != next)) {
    122 + rq->preempted = rq->cache_ticks = 0;
    123 next->timestamp = now;
    124 rq->nr_switches++;
    125 rq->curr = next;
    126 @@ -6625,7 +6648,7 @@ void __init sched_init(void)
    127 rq = cpu_rq(i);
    128 spin_lock_init(&rq->lock);
    129 lockdep_set_class(&rq->lock, &rq->rq_lock_key);
    130 - rq->nr_running = 0;
    131 + rq->nr_running = rq->cache_ticks = rq->preempted = 0;
    132
    133 #ifdef CONFIG_SMP
    134 rq->sd = NULL;
    135 Index: linux-2.6.20-ck1/kernel/sysctl.c
    136 ===================================================================
    137 --- linux-2.6.20-ck1.orig/kernel/sysctl.c 2007-02-16 19:01:30.000000000 +1100
    138 +++ linux-2.6.20-ck1/kernel/sysctl.c 2007-02-16 19:01:30.000000000 +1100
    139 @@ -684,6 +684,14 @@ static ctl_table kern_table[] = {
    140 .mode = 0644,
    141 .proc_handler = &proc_dointvec,
    142 },
    143 + {
    144 + .ctl_name = CTL_UNNUMBERED,
    145 + .procname = "compute",
    146 + .data = &sched_compute,
    147 + .maxlen = sizeof (int),
    148 + .mode = 0644,
    149 + .proc_handler = &proc_dointvec,
    150 + },
    151 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
    152 {
    153 .ctl_name = KERN_UNKNOWN_NMI_PANIC,
    154 Index: linux-2.6.20-ck1/Documentation/sysctl/kernel.txt
    155 ===================================================================
    156 --- linux-2.6.20-ck1.orig/Documentation/sysctl/kernel.txt 2007-02-16 19:01:30.000000000 +1100
    157 +++ linux-2.6.20-ck1/Documentation/sysctl/kernel.txt 2007-02-16 19:01:30.000000000 +1100
    158 @@ -18,6 +18,7 @@ Currently, these files might (depending
    159 show up in /proc/sys/kernel:
    160 - acpi_video_flags
    161 - acct
    162 +- compute
    163 - core_pattern
    164 - core_uses_pid
    165 - ctrl-alt-del
    166 @@ -85,6 +86,16 @@ valid for 30 seconds.
    167
    168 ==============================================================
    169
    170 +compute:
    171 +
    172 +This flag controls the long timeslice, delayed preemption mode in the
    173 +cpu scheduler suitable for scientific computation applications. It
    174 +leads to large latencies so is unsuitable for normal usage.
    175 +
    176 +Disabled by default.
    177 +
    178 +==============================================================
    179 +
    180 core_pattern:
    181
    182 core_pattern is used to specify a core dumpfile pattern name.