Robert Love wrote:
>
> During 2.5.5-pre, an optimization was made that removed schedule_tail
> from UP kernels. This causes the initial preempt_count of a new task,
> which starts at 1, to never decrement to zero and thus never become
> preemptible.
>
> Thanks to everyone who pointed out the lousy performance - it took
> awhile to find but it should be fixed now. Please comment if not.
>
> Patch is against 2.5.6-pre2 and is critical for all UP+preempt users.
With out a lot of looking, wouldn't it be easier to just change fork?
-g
>
> Robert Love
>
> diff -urN linux-2.5.6-pre2/arch/alpha/kernel/entry.S linux/arch/alpha/kernel/entry.S
> --- linux-2.5.6-pre2/arch/alpha/kernel/entry.S Fri Mar 1 17:21:14 2002
> +++ linux/arch/alpha/kernel/entry.S Mon Mar 4 17:49:27 2002
> @@ -495,7 +495,7 @@
> ret $31,($26),1
> .end alpha_switch_to
>
> -#ifdef CONFIG_SMP
> +#ifdef CONFIG_SMP || CONFIG_PREEMPT
> .globl ret_from_fork
> .align 3
> .ent ret_from_fork
> diff -urN linux-2.5.6-pre2/arch/i386/kernel/entry.S linux/arch/i386/kernel/entry.S
> --- linux-2.5.6-pre2/arch/i386/kernel/entry.S Tue Feb 19 21:10:58 2002
> +++ linux/arch/i386/kernel/entry.S Mon Mar 4 17:48:32 2002
> @@ -195,7 +195,7 @@
>
>
> ENTRY(ret_from_fork)
> -#if CONFIG_SMP
> +#if CONFIG_SMP || CONFIG_PREEMPT
> call SYMBOL_NAME(schedule_tail)
> #endif
> GET_THREAD_INFO(%ebx)
> diff -urN linux-2.5.6-pre2/arch/ppc/kernel/entry.S linux/arch/ppc/kernel/entry.S
> --- linux-2.5.6-pre2/arch/ppc/kernel/entry.S Tue Feb 19 21:10:59 2002
> +++ linux/arch/ppc/kernel/entry.S Mon Mar 4 17:48:41 2002
> @@ -343,7 +343,7 @@
>
> .globl ret_from_fork
> ret_from_fork:
> -#ifdef CONFIG_SMP
> +#ifdef CONFIG_SMP || CONFIG_PREEMPT
> bl schedule_tail
> #endif
> rlwinm r3,r1,0,0,18
> diff -urN linux-2.5.6-pre2/arch/ppc64/kernel/entry.S linux/arch/ppc64/kernel/entry.S
> --- linux-2.5.6-pre2/arch/ppc64/kernel/entry.S Tue Feb 19 21:10:53 2002
> +++ linux/arch/ppc64/kernel/entry.S Mon Mar 4 17:52:16 2002
> @@ -311,7 +311,7 @@
> blr
>
> _GLOBAL(ret_from_fork)
> -#ifdef CONFIG_SMP
> +#ifdef CONFIG_SMP || CONFIG_PREEMPT
> bl .schedule_tail
> #endif
> clrrdi r4,r1,THREAD_SHIFT
> diff -urN linux-2.5.6-pre2/arch/s390/kernel/entry.S linux/arch/s390/kernel/entry.S
> --- linux-2.5.6-pre2/arch/s390/kernel/entry.S Tue Feb 19 21:10:57 2002
> +++ linux/arch/s390/kernel/entry.S Mon Mar 4 17:48:12 2002
> @@ -295,7 +295,7 @@
> stosm 24(%r15),0x03 # reenable interrupts
> sr %r0,%r0 # child returns 0
> st %r0,SP_R2(%r15) # store return value (change R2 on stack)
> -#ifdef CONFIG_SMP
> +#ifdef CONFIG_SMP || CONFIG_PREEMPT
> l %r1,BASED(.Lschedtail)
> la %r14,BASED(sysc_return)
> br %r1 # call schedule_tail, return to sysc_return
> @@ -896,7 +896,7 @@
> #error .Ltrace: .long syscall_trace
> .Lvfork: .long sys_vfork
>
> -#ifdef CONFIG_SMP
> +#ifdef CONFIG_SMP || CONFIG_PREEMPT
> .Lschedtail: .long schedule_tail
> #endif
>
> diff -urN linux-2.5.6-pre2/arch/s390x/kernel/entry.S linux/arch/s390x/kernel/entry.S
> --- linux-2.5.6-pre2/arch/s390x/kernel/entry.S Tue Feb 19 21:10:58 2002
> +++ linux/arch/s390x/kernel/entry.S Mon Mar 4 17:53:31 2002
> @@ -280,7 +280,7 @@
> GET_CURRENT # load pointer to task_struct to R9
> stosm 48(%r15),0x03 # reenable interrupts
> xc SP_R2(8,%r15),SP_R2(%r15) # child returns 0
> -#ifdef CONFIG_SMP
> +#ifdef CONFIG_SMP || CONFIG_PREEMPT
> larl %r14,sysc_return
> jg schedule_tail # return to sysc_return
> #else
> diff -urN linux-2.5.6-pre2/kernel/sched.c linux/kernel/sched.c
> --- linux-2.5.6-pre2/kernel/sched.c Fri Mar 1 17:21:16 2002
> +++ linux/kernel/sched.c Mon Mar 4 17:54:00 2002
> @@ -397,7 +397,7 @@
> p->sleep_avg) / (EXIT_WEIGHT + 1);
> }
>
> -#if CONFIG_SMP
> +#if CONFIG_SMP || CONFIG_PREEMPT
> asmlinkage void schedule_tail(void)
> {
> spin_unlock_irq(&this_rq()->lock);
>
> -
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-- George george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Real time sched: http://sourceforge.net/projects/rtsched/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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