From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jack Steiner Date: Tue, 27 Mar 2007 19:30:19 +0000 Subject: Re: [PATCH] - Speed up boot - skip unnecessary clock calibration Message-Id: <20070327193019.GA24749@sgi.com> List-Id: References: <20070327132953.GA14401@sgi.com> In-Reply-To: <20070327132953.GA14401@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Skip clock calibration if cpu being brought online is exactly the same speed, stepping, etc., as the previous cpu. This significantly reduces the time to boot very large systems. Signed-off-by: Jack Steiner ---- Add suggestion from Matthew Wilcox to use local variables to shorten lines. Index: linux/arch/ia64/kernel/smpboot.c =================================--- linux.orig/arch/ia64/kernel/smpboot.c 2007-03-27 10:08:13.664475719 -0500 +++ linux/arch/ia64/kernel/smpboot.c 2007-03-27 14:20:44.070836177 -0500 @@ -375,6 +375,7 @@ static void __devinit smp_callin (void) { int cpuid, phys_id, itc_master; + struct cpuinfo_ia64 *last_cpuinfo, *this_cpuinfo; extern void ia64_init_itm(void); extern volatile int time_keeper_id; @@ -424,7 +425,21 @@ smp_callin (void) * Get our bogomips. */ ia64_init_itm(); - calibrate_delay(); + + /* + * Delay calibration can be skipped if new processor is identical to the + * previous processor. + */ + last_cpuinfo = cpu_data(cpuid - 1); + this_cpuinfo = local_cpu_data; + if (last_cpuinfo->itc_freq != this_cpuinfo->itc_freq || + last_cpuinfo->proc_freq != this_cpuinfo->proc_freq || + last_cpuinfo->features != this_cpuinfo->features || + last_cpuinfo->revision != this_cpuinfo->revision || + last_cpuinfo->family != this_cpuinfo->family || + last_cpuinfo->archrev != this_cpuinfo->archrev || + last_cpuinfo->model != this_cpuinfo->model) + calibrate_delay(); local_cpu_data->loops_per_jiffy = loops_per_jiffy; #ifdef CONFIG_IA32_SUPPORT