diff options
| author | Len Brown <len.brown@intel.com> | 2015-11-23 02:16:15 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-11-23 11:08:33 +0300 |
| commit | 2fde46b79e2fdbc90d0d97cf992782732b5a371c (patch) | |
| tree | b98b4ca898b9f55111f9921b46bdc729042e6955 | |
| parent | 72613184a1f076659e8a902d64351f50d3f9c990 (diff) | |
| download | linux-2fde46b79e2fdbc90d0d97cf992782732b5a371c.tar.xz | |
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 <shrybman@teksavvy.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dparsons@brightdsl.net
Link: http://lkml.kernel.org/r/9082eb809ef40dad02db714759c7aaf618c518d4.1448232494.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 892ee2e5ecbc..fbabe4fcc7fb 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; } |