Commit-ID: 2fde46b79e2fdbc90d0d97cf992782732b5a371c
Gitweb: http://git.kernel.org/tip/2fde46b79e2fdbc90d0d97cf992782732b5a371c
Author: Len Brown <len.br...@intel.com>
AuthorDate: Sun, 22 Nov 2015 18:16:15 -0500
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Mon, 23 Nov 2015 09:08:33 +0100
x86/smpboot: Re-enable init_udelay=0 by default on modern CPUs
Fix a Linux-4.3 corner case performance regression, introduced by commit:
f1ccd249319e ("x86/smpboot: Fix cpu_init_udelay=10000 corner case boot
parameter misbehavior")
which allowed the cmdline "cpu_init_udelay=" to work with all values,
including the default of 10000.
But in setting the default of 10000, it over-rode the code stat sets
the delay 0 on modern processors.
Also, tidy up use of INT/UINT.
Reported-by: Shane <shryb...@teksavvy.com>
Signed-off-by: Len Brown <len.br...@intel.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: dpars...@brightdsl.net
Link:
http://lkml.kernel.org/r/9082eb809ef40dad02db714759c7aaf618c518d4.1448232494.git.len.br...@intel.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
arch/x86/kernel/smpboot.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 892ee2e5..fbabe4f 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -509,7 +509,7 @@ void __inquire_remote_apic(int apicid)
*/
#define UDELAY_10MS_DEFAULT 10000
-static unsigned int init_udelay = INT_MAX;
+static unsigned int init_udelay = UINT_MAX;
static int __init cpu_init_udelay(char *str)
{
@@ -522,14 +522,15 @@ 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 != INT_MAX)
+ if (init_udelay != UINT_MAX)
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)))
+ ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && (boot_cpu_data.x86
>= 0xF))) {
init_udelay = 0;
-
+ return;
+ }
/* else, use legacy delay */
init_udelay = UDELAY_10MS_DEFAULT;
}
--
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