Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 11 Jan 2002 12:07:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 11 Jan 2002 12:07:34 -0500 Received: from artemis.rus.uni-stuttgart.de ([129.69.1.28]:60099 "EHLO artemis.rus.uni-stuttgart.de") by vger.kernel.org with ESMTP id ; Fri, 11 Jan 2002 12:07:18 -0500 Message-ID: <3C3F1BB8.C666F57@hlrs.de> Date: Fri, 11 Jan 2002 18:07:04 +0100 From: Rainer Keller Organization: Rechenzentrum =?iso-8859-1?Q?Universit=E4t?= Stuttgart X-Mailer: Mozilla 4.78 [en] (X11; U; Linux 2.4.17 i686) X-Accept-Language: de, en MIME-Version: 1.0 To: Jeff Garzik CC: linux-kernel@vger.kernel.org, Marcelo Tosatti Subject: Re: [PATCH] Small optimization for UP in sched and prefetch (take 3) In-Reply-To: <3C3EBF76.3AEB82AB@hlrs.de> <3C3EC3A2.C9C9D184@mandrakesoft.com> Content-Type: multipart/mixed; boundary="------------62E47A84FD5C9077C3204CC6" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------62E47A84FD5C9077C3204CC6 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Jeff Garzik wrote: > > PS: Because of usage of prefetch in include/linux/list.h, the > > memory prefetch is triggered 137 times on my configuration... > We need to merge in __builtin_prefetch support into the kernel, > because gcc 3.1 recently got support for it. It would be nice at > least for future prefetch-related patches to perhaps call > __builtin_prefetch, and have the headers substitute a prefetch if > the compiler does not support it. OK, I added this suggestion -- it changes compiler.h to look out for gcc-3.1 and then set macros for __builtin_prefetch. But in order to get gcc 3.1 to issue prefetches, the -mcpu (and/or -march?) must be set to pentium3 or pentium4 (same applies for AMD athlons). There's one minor nit to this: "copy_to_user" has declared the parameter "from" as const and then does a prefetch on "from".... This produces a warning: /usr/src/linux-2.4.17-mine/include/asm/uaccess.h: In function `__constant_copy_to_user': /usr/src/linux-2.4.17-mine/include/asm/uaccess.h:549: warning: passing arg 1 of `__builtin_prefetch' discards qualifiers from pointer target type How can I resolve this ? Greetings, raY -- --------------------------------------------------------------- Rainer Keller Mail: Keller@hlrs.de Allmandring 30 WWW: http://www.hlrs.de/people/keller 70550 Stuttgart Tel. 0711 / 685 5858 --------------62E47A84FD5C9077C3204CC6 Content-Type: text/plain; charset=us-ascii; name="patch_prefetch_sched-2.4.17_third.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="patch_prefetch_sched-2.4.17_third.diff" diff -ur linux-2.4.17/include/asm-i386/processor.h linux-2.4.17-mine/include/asm-i386/processor.h --- linux-2.4.17/include/asm-i386/processor.h Thu Nov 22 20:46:19 2001 +++ linux-2.4.17-mine/include/asm-i386/processor.h Fri Jan 11 13:27:30 2002 @@ -478,8 +478,14 @@ #define cpu_relax() rep_nop() -/* Prefetch instructions for Pentium III and AMD Athlon */ -#ifdef CONFIG_MPENTIUMIII +/* + * If we don't have a compiler, which offers builtin_prefetch, do it our selve, + * if the processor supports it. + */ +#ifndef HAVE_builtin_prefetch + +/* Prefetch instructions for Pentium III, Pentium 4 and AMD Athlon */ +#if defined(CONFIG_MPENTIUMIII) || defined(CONFIG_MPENTIUM4) #define ARCH_HAS_PREFETCH extern inline void prefetch(const void *x) @@ -502,8 +508,14 @@ { __asm__ __volatile__ ("prefetchw (%0)" : : "r"(x)); } -#define spin_lock_prefetch(x) prefetchw(x) +#ifndef CONFIG_SMP +#define spin_lock_prefetch(x) do { } while(0) +#else +#define spin_lock_prefetch(x) prefetchw(x) #endif + +#endif /* CONFIG_MPENTIUMII || CONFIG_MPENTIUM4 */ +#endif /* HAVE_builtin_prefetch */ #endif /* __ASM_I386_PROCESSOR_H */ diff -ur linux-2.4.17/include/linux/compiler.h linux-2.4.17-mine/include/linux/compiler.h --- linux-2.4.17/include/linux/compiler.h Tue Sep 18 23:12:45 2001 +++ linux-2.4.17-mine/include/linux/compiler.h Fri Jan 11 13:19:40 2002 @@ -1,6 +1,8 @@ #ifndef __LINUX_COMPILER_H #define __LINUX_COMPILER_H +#include + /* Somewhere in the middle of the GCC 2.96 development cycle, we implemented a mechanism by which the user can annotate likely branch directions and expect the blocks to be reordered appropriately. Define __builtin_expect @@ -12,5 +14,24 @@ #define likely(x) __builtin_expect((x),1) #define unlikely(x) __builtin_expect((x),0) + + +/* + * Starting somewhere in GCC 3.1, builtin_prefetch support was added, i.e. we're + * not dependant on information by include/asm/processor.h + */ +#if __GNUC__ == 3 && __GNUC_MINOR__ >= 1 +#define HAVE_builtin_prefetch + +#define prefetch(x) __builtin_prefetch((x)) +#define prefetchw(x) __builtin_prefetch((x), 2) + +#ifndef CONFIG_SMP +#define spin_lock_prefetch(x) do { } while(0) +#else +#define spin_lock_prefetch(x) prefetchw(x) +#endif + +#endif #endif /* __LINUX_COMPILER_H */ diff -ur linux-2.4.17/include/linux/prefetch.h linux-2.4.17-mine/include/linux/prefetch.h --- linux-2.4.17/include/linux/prefetch.h Thu Nov 22 20:46:19 2001 +++ linux-2.4.17-mine/include/linux/prefetch.h Fri Jan 11 12:44:30 2002 @@ -10,6 +10,8 @@ #ifndef _LINUX_PREFETCH_H #define _LINUX_PREFETCH_H +#include +#include #include #include @@ -26,7 +28,9 @@ prefetch(x) - prefetches the cacheline at "x" for read prefetchw(x) - prefetches the cacheline at "x" for write - spin_lock_prefetch(x) - prefectches the spinlock *x for taking + spin_lock_prefetch(x) - prefetches the spinlock *x for taking, + if on SMP, otherwise not needed + (except for debugging reasons -- slow anyway). there is also PREFETCH_STRIDE which is the architecure-prefered "lookahead" size for prefetching streamed operations. @@ -37,7 +41,9 @@ * These cannot be do{}while(0) macros. See the mental gymnastics in * the loop macro. */ - + +#ifndef HAVE_builtin_prefetch + #ifndef ARCH_HAS_PREFETCH #define ARCH_HAS_PREFETCH static inline void prefetch(const void *x) {;} @@ -50,11 +56,17 @@ #ifndef ARCH_HAS_SPINLOCK_PREFETCH #define ARCH_HAS_SPINLOCK_PREFETCH +#ifndef CONFIG_SMP +#define spin_lock_prefetch(x) do { } while(0) +#else #define spin_lock_prefetch(x) prefetchw(x) #endif +#endif #ifndef PREFETCH_STRIDE #define PREFETCH_STRIDE (4*L1_CACHE_BYTES) #endif + +#endif /* HAVE_builtin_prefetch */ #endif diff -ur linux-2.4.17/kernel/sched.c linux-2.4.17-mine/kernel/sched.c --- linux-2.4.17/kernel/sched.c Fri Dec 21 18:42:04 2001 +++ linux-2.4.17-mine/kernel/sched.c Fri Jan 11 11:30:43 2002 @@ -117,11 +117,13 @@ #define idle_task(cpu) (init_tasks[cpu_number_map(cpu)]) #define can_schedule(p,cpu) \ ((p)->cpus_runnable & (p)->cpus_allowed & (1 << cpu)) +#define processor_of_tsk(tsk) (tsk)->processor #else #define idle_task(cpu) (&init_task) #define can_schedule(p,cpu) (1) +#define processor_of_tsk(tsk) (0) #endif @@ -172,7 +174,7 @@ #ifdef CONFIG_SMP /* Give a largish advantage to the same processor... */ /* (this is equivalent to penalizing other processors) */ - if (p->processor == this_cpu) + if (processor_of_tsk(p) == this_cpu) weight += PROC_CHANGE_PENALTY; #endif @@ -221,7 +223,7 @@ * shortcut if the woken up task's last CPU is * idle now. */ - best_cpu = p->processor; + best_cpu = processor_of_tsk(p); if (can_schedule(p, best_cpu)) { tsk = idle_task(best_cpu); if (cpu_curr(best_cpu) == tsk) { @@ -295,18 +297,18 @@ tsk = target_tsk; if (tsk) { if (oldest_idle != -1ULL) { - best_cpu = tsk->processor; + best_cpu = processor_of_tsk(tsk); goto send_now_idle; } tsk->need_resched = 1; - if (tsk->processor != this_cpu) - smp_send_reschedule(tsk->processor); + if (processor_of_tsk(tsk) != this_cpu) + smp_send_reschedule(processor_of_tsk(tsk)); } return; #else /* UP */ - int this_cpu = smp_processor_id(); + const int this_cpu = smp_processor_id(); struct task_struct *tsk; tsk = cpu_curr(this_cpu); @@ -559,7 +561,7 @@ if (!current->active_mm) BUG(); need_resched_back: prev = current; - this_cpu = prev->processor; + this_cpu = processor_of_tsk(prev); if (unlikely(in_interrupt())) { printk("Scheduling in interrupt\n"); @@ -1311,7 +1313,7 @@ } sched_data->curr = current; sched_data->last_schedule = get_cycles(); - clear_bit(current->processor, &wait_init_idle); + clear_bit(processor_of_tsk(current), &wait_init_idle); } extern void init_timervecs (void); --------------62E47A84FD5C9077C3204CC6-- - 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/