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    SubjectRe: UP optimizations ..
    Herbert =?iso-8859-1?Q?P=F6tzl?= writes:
    >
    > Hi Mikael!
    > Hi Marcelo!
    >
    > stumbled repeatedly over the patches (or what remained of them)
    > from Mikael?, replacing task->processor and friends by inline
    > functions task_cpu(task), to eliminate them on UP systems ...
    >
    > my questions:
    > - is there an up to date patchset?

    Yes, I've kept it up to date. In fact I've been using it in
    every single 2.4 kernel I've built for the last 18+ months.
    Lately also on ppc32 and x86-64.

    Below is the current UP micro-optimisation patch set for 2.4.22.
    It changes p->processor, p->cpus_allowed, and p->cpus_runnable
    accesses (reads and writes) to use inline functions. In UP kernels
    these reduce to doing nothing or returning a constant.

    To keep the patch small, it doesn't change accesses in SMP-only code.
    (This is also the reason why p->cpus_runnable only has a wrapper for
    updates, since all reads are in SMP-only code.)

    /Mikael

    diff -ruN linux-2.4.22/fs/proc/array.c linux-2.4.22.up-opt/fs/proc/array.c
    --- linux-2.4.22/fs/proc/array.c 2003-06-14 13:30:27.000000000 +0200
    +++ linux-2.4.22.up-opt/fs/proc/array.c 2003-08-27 19:42:34.159566477 +0200
    @@ -390,7 +390,7 @@
    task->nswap,
    task->cnswap,
    task->exit_signal,
    - task->processor);
    + task_cpu(task));
    if(mm)
    mmput(mm);
    return res;
    diff -ruN linux-2.4.22/include/linux/sched.h linux-2.4.22.up-opt/include/linux/sched.h
    --- linux-2.4.22/include/linux/sched.h 2003-06-14 13:30:29.000000000 +0200
    +++ linux-2.4.22.up-opt/include/linux/sched.h 2003-08-27 19:42:34.161566172 +0200
    @@ -559,17 +559,77 @@
    return p;
    }

    +/*
    + * Wrappers for p->processor/cpus_allowed/cpus_runnable access. No-op on UP.
    + */
    +#ifdef CONFIG_SMP
    +
    +static inline int task_cpu(const struct task_struct *p)
    +{
    + return p->processor;
    +}
    +
    +static inline void set_task_cpu(struct task_struct *p, int cpu)
    +{
    + p->processor = cpu;
    +}
    +
    +static inline unsigned long task_cpus_allowed(const struct task_struct *p)
    +{
    + return p->cpus_allowed;
    +}
    +
    +static inline void set_task_cpus_allowed(struct task_struct *p,
    + unsigned long cpus_allowed)
    +{
    + p->cpus_allowed = cpus_allowed;
    +}
    +
    +static inline void set_task_cpus_runnable(struct task_struct *p,
    + unsigned long cpus_runnable)
    +{
    + p->cpus_runnable = cpus_runnable;
    +}
    +
    +#else
    +
    +static inline int task_cpu(const struct task_struct *p)
    +{
    + return 0;
    +}
    +
    +static inline void set_task_cpu(struct task_struct *p, int cpu)
    +{
    +}
    +
    +static inline unsigned long task_cpus_allowed(const struct task_struct *p)
    +{
    + return ~0UL;
    +}
    +
    +static inline void set_task_cpus_allowed(struct task_struct *p,
    + unsigned long cpus_allowed)
    +{
    +}
    +
    +static inline void set_task_cpus_runnable(struct task_struct *p,
    + unsigned long cpus_runnable)
    +{
    +}
    +
    +#endif /* CONFIG_SMP */
    +
    #define task_has_cpu(tsk) ((tsk)->cpus_runnable != ~0UL)

    static inline void task_set_cpu(struct task_struct *tsk, unsigned int cpu)
    {
    - tsk->processor = cpu;
    - tsk->cpus_runnable = 1UL << cpu;
    + set_task_cpu(tsk, cpu);
    + set_task_cpus_runnable(tsk, 1UL << cpu);
    }

    static inline void task_release_cpu(struct task_struct *tsk)
    {
    - tsk->cpus_runnable = ~0UL;
    + set_task_cpus_runnable(tsk, ~0UL);
    }

    /* per-UID process charging. */
    diff -ruN linux-2.4.22/kernel/sched.c linux-2.4.22.up-opt/kernel/sched.c
    --- linux-2.4.22/kernel/sched.c 2003-08-25 20:07:50.000000000 +0200
    +++ linux-2.4.22.up-opt/kernel/sched.c 2003-08-27 19:42:34.163565866 +0200
    @@ -359,7 +359,7 @@
    if (task_on_runqueue(p))
    goto out;
    add_to_runqueue(p);
    - if (!synchronous || !(p->cpus_allowed & (1UL << smp_processor_id())))
    + if (!synchronous || !(task_cpus_allowed(p) & (1UL << smp_processor_id())))
    reschedule_idle(p);
    success = 1;
    out:
    @@ -557,7 +557,7 @@
    BUG_ON(!current->active_mm);
    need_resched_back:
    prev = current;
    - this_cpu = prev->processor;
    + this_cpu = task_cpu(prev);

    if (unlikely(in_interrupt())) {
    printk("Scheduling in interrupt\n");
    @@ -1364,7 +1364,7 @@
    }
    sched_data->curr = current;
    sched_data->last_schedule = get_cycles();
    - clear_bit(current->processor, &wait_init_idle);
    + clear_bit(task_cpu(current), &wait_init_idle);
    }

    extern void init_timervecs (void);
    @@ -1378,7 +1378,7 @@
    int cpu = smp_processor_id();
    int nr;

    - init_task.processor = cpu;
    + set_task_cpu(&init_task, cpu);

    for(nr = 0; nr < PIDHASH_SZ; nr++)
    pidhash[nr] = NULL;
    diff -ruN linux-2.4.22/kernel/softirq.c linux-2.4.22.up-opt/kernel/softirq.c
    --- linux-2.4.22/kernel/softirq.c 2002-11-30 17:12:32.000000000 +0100
    +++ linux-2.4.22.up-opt/kernel/softirq.c 2003-08-27 19:42:34.164565713 +0200
    @@ -368,7 +368,7 @@
    sigfillset(&current->blocked);

    /* Migrate to the right CPU */
    - current->cpus_allowed = 1UL << cpu;
    + set_task_cpus_allowed(current, 1UL << cpu);
    while (smp_processor_id() != cpu)
    schedule();

    -
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