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Commit 1a744cb3 authored by Len Brown's avatar Len Brown Committed by Ingo Molnar
Browse files

x86/smp/boot: Remove 10ms delay from cpu_up() on modern processors 



Modern processor familes do not require the 10ms delay
in cpu_up() to de-assert INIT.  This speeds up boot
and resume by 10ms per (application) processor.

Signed-off-by: default avatarLen Brown <len.brown@intel.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan H. Schönherr <jschoenh@amazon.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/021ce30c88f216ad39686646421194dc25671e55.1431379433.git.len.brown@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d68921f9

arch/x86/kernel/smpboot.c

+15 −0
Original line number Diff line number Diff line
@@ -521,6 +521,7 @@ void __inquire_remote_apic(int apicid) 
 * many cores and don't require that delay.

 *

 * Cmdline "init_cpu_udelay=" is available to over-ride this delay.

 * Modern processor families are quirked to remove the delay entirely.

 */

#define UDELAY_10MS_DEFAULT 10000
@@ -534,6 +535,18 @@ static int __init cpu_init_udelay(char *str) 
}

early_param("cpu_init_udelay", cpu_init_udelay);



static void __init smp_quirk_init_udelay(void)

{

	/* if cmdline changed it from default, leave it alone */

	if (init_udelay != UDELAY_10MS_DEFAULT)

		return;



	/* if modern processor, use no delay */

	if (((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) && (boot_cpu_data.x86 == 6)) ||

	    ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && (boot_cpu_data.x86 >= 0xF)))

		init_udelay = 0;

}



/*

 * Poke the other CPU in the eye via NMI to wake it up. Remember that the normal

 * INIT, INIT, STARTUP sequence will reset the chip hard for us, and this
@@ -1210,6 +1223,8 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) 
		uv_system_init();



	set_mtrr_aps_delayed_init();



	smp_quirk_init_udelay();

}



void arch_enable_nonboot_cpus_begin(void)