From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756344AbXD2K6M (ORCPT ); Sun, 29 Apr 2007 06:58:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756367AbXD2K5u (ORCPT ); Sun, 29 Apr 2007 06:57:50 -0400 Received: from mx1.suse.de ([195.135.220.2]:52221 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756344AbXD2Kxj (ORCPT ); Sun, 29 Apr 2007 06:53:39 -0400 From: Andi Kleen References: <200704291252.514680000@suse.de> In-Reply-To: <200704291252.514680000@suse.de> To: Eric Dumazet , patches@x86-64.org, linux-kernel@vger.kernel.org Subject: [PATCH] [44/48] x86_64: vsyscall_gtod_data diet and vgettimeofday() fix Message-Id: <20070429105334.AE68A151C5@wotan.suse.de> Date: Sun, 29 Apr 2007 12:53:34 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet Current vsyscall_gtod_data is large (3 or 4 cache lines dirtied at timer interrupt). We can shrink it to exactly 64 bytes (1 cache line on AMD64) Instead of copying a whole struct clocksource, we copy only needed fields. I deleted an unused field : offset_base This patch fixes one oddity in vgettimeofday(): It can returns a timeval with tv_usec = 1000000. Maybe not a bug, but why not doing the right thing ? Signed-off-by: Eric Dumazet Signed-off-by: Andi Kleen --- arch/x86_64/kernel/vsyscall.c | 53 ++++++++++++++++++++++++++++-------------- 1 file changed, 36 insertions(+), 17 deletions(-) Index: linux/arch/x86_64/kernel/vsyscall.c =================================================================== --- linux.orig/arch/x86_64/kernel/vsyscall.c +++ linux/arch/x86_64/kernel/vsyscall.c @@ -51,13 +51,28 @@ asm("" : "=r" (v) : "0" (x)); \ ((v - VSYSCALL_FIRST_PAGE) + __pa_symbol(&__vsyscall_0)); }) +/* + * vsyscall_gtod_data contains data that is : + * - readonly from vsyscalls + * - writen by timer interrupt or systcl (/proc/sys/kernel/vsyscall64) + * Try to keep this structure as small as possible to avoid cache line ping pongs + */ struct vsyscall_gtod_data_t { - seqlock_t lock; - int sysctl_enabled; - struct timeval wall_time_tv; + seqlock_t lock; + + /* open coded 'struct timespec' */ + time_t wall_time_sec; + u32 wall_time_nsec; + + int sysctl_enabled; struct timezone sys_tz; - cycle_t offset_base; - struct clocksource clock; + struct { /* extract of a clocksource struct */ + cycle_t (*vread)(void); + cycle_t cycle_last; + cycle_t mask; + u32 mult; + u32 shift; + } clock; }; int __vgetcpu_mode __section_vgetcpu_mode; @@ -73,9 +88,13 @@ void update_vsyscall(struct timespec *wa write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags); /* copy vsyscall data */ - vsyscall_gtod_data.clock = *clock; - vsyscall_gtod_data.wall_time_tv.tv_sec = wall_time->tv_sec; - vsyscall_gtod_data.wall_time_tv.tv_usec = wall_time->tv_nsec/1000; + vsyscall_gtod_data.clock.vread = clock->vread; + vsyscall_gtod_data.clock.cycle_last = clock->cycle_last; + vsyscall_gtod_data.clock.mask = clock->mask; + vsyscall_gtod_data.clock.mult = clock->mult; + vsyscall_gtod_data.clock.shift = clock->shift; + vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec; + vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec; vsyscall_gtod_data.sys_tz = sys_tz; write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags); } @@ -110,7 +129,8 @@ static __always_inline long time_syscall static __always_inline void do_vgettimeofday(struct timeval * tv) { cycle_t now, base, mask, cycle_delta; - unsigned long seq, mult, shift, nsec_delta; + unsigned seq; + unsigned long mult, shift, nsec; cycle_t (*vread)(void); do { seq = read_seqbegin(&__vsyscall_gtod_data.lock); @@ -126,21 +146,20 @@ static __always_inline void do_vgettimeo mult = __vsyscall_gtod_data.clock.mult; shift = __vsyscall_gtod_data.clock.shift; - *tv = __vsyscall_gtod_data.wall_time_tv; - + tv->tv_sec = __vsyscall_gtod_data.wall_time_sec; + nsec = __vsyscall_gtod_data.wall_time_nsec; } while (read_seqretry(&__vsyscall_gtod_data.lock, seq)); /* calculate interval: */ cycle_delta = (now - base) & mask; /* convert to nsecs: */ - nsec_delta = (cycle_delta * mult) >> shift; + nsec += (cycle_delta * mult) >> shift; - /* convert to usecs and add to timespec: */ - tv->tv_usec += nsec_delta / NSEC_PER_USEC; - while (tv->tv_usec > USEC_PER_SEC) { + while (nsec >= NSEC_PER_SEC) { tv->tv_sec += 1; - tv->tv_usec -= USEC_PER_SEC; + nsec -= NSEC_PER_SEC; } + tv->tv_usec = nsec / NSEC_PER_USEC; } int __vsyscall(0) vgettimeofday(struct timeval * tv, struct timezone * tz) @@ -159,7 +178,7 @@ time_t __vsyscall(1) vtime(time_t *t) time_t result; if (unlikely(!__vsyscall_gtod_data.sysctl_enabled)) return time_syscall(t); - result = __vsyscall_gtod_data.wall_time_tv.tv_sec; + result = __vsyscall_gtod_data.wall_time_sec; if (t) *t = result; return result;