From 0f0b7e1cc7abf8e1a8b301f2868379d611d05ae2 Mon Sep 17 00:00:00 2001 From: Juri Lelli Date: Thu, 7 Mar 2019 13:09:13 +0100 Subject: x86/tsc: Add option to disable tsc clocksource watchdog Clocksource watchdog has been found responsible for generating latency spikes (in the 10-20 us range) when woken up to check for TSC stability. Add an option to disable it at boot. Signed-off-by: Juri Lelli Signed-off-by: Thomas Gleixner Cc: bigeasy@linutronix.de Cc: linux-rt-users@vger.kernel.org Cc: peterz@infradead.org Cc: bristot@redhat.com Cc: williams@redhat.com Link: https://lkml.kernel.org/r/20190307120913.13168-1-juri.lelli@redhat.com --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ arch/x86/kernel/tsc.c | 5 ++++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2b8ee90bb644..c4d830003b21 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4703,6 +4703,10 @@ [x86] unstable: mark the TSC clocksource as unstable, this marks the TSC unconditionally unstable at bootup and avoids any further wobbles once the TSC watchdog notices. + [x86] nowatchdog: disable clocksource watchdog. Used + in situations with strict latency requirements (where + interruptions from clocksource watchdog are not + acceptable). turbografx.map[2|3]= [HW,JOY] TurboGraFX parallel port interface diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 3fae23834069..aab0c82e0a0d 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -283,6 +283,7 @@ int __init notsc_setup(char *str) __setup("notsc", notsc_setup); static int no_sched_irq_time; +static int no_tsc_watchdog; static int __init tsc_setup(char *str) { @@ -292,6 +293,8 @@ static int __init tsc_setup(char *str) no_sched_irq_time = 1; if (!strcmp(str, "unstable")) mark_tsc_unstable("boot parameter"); + if (!strcmp(str, "nowatchdog")) + no_tsc_watchdog = 1; return 1; } @@ -1349,7 +1352,7 @@ static int __init init_tsc_clocksource(void) if (tsc_unstable) goto unreg; - if (tsc_clocksource_reliable) + if (tsc_clocksource_reliable || no_tsc_watchdog) clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY; if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3)) -- cgit v1.2.3 From 81423c37415fe45057d64196ae0ce8e17a9c7148 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Fri, 29 Mar 2019 17:47:38 -0700 Subject: x86/timer: Don't inline __const_udelay() LTO will happily inline __const_udelay() everywhere it is used. Forcing it noinline saves ~44k text in a LTO build. 13999560 1740864 1499136 17239560 1070e08 vmlinux-with-udelay-inline 13954764 1736768 1499136 17190668 1064f0c vmlinux-wo-udelay-inline Even without LTO this function should never be inlined. Signed-off-by: Andi Kleen Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20190330004743.29541-4-andi@firstfloor.org --- arch/x86/lib/delay.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c index f5b7f1b3b6d7..b7375dc6898f 100644 --- a/arch/x86/lib/delay.c +++ b/arch/x86/lib/delay.c @@ -162,7 +162,7 @@ void __delay(unsigned long loops) } EXPORT_SYMBOL(__delay); -void __const_udelay(unsigned long xloops) +noinline void __const_udelay(unsigned long xloops) { unsigned long lpj = this_cpu_read(cpu_info.loops_per_jiffy) ? : loops_per_jiffy; int d0; -- cgit v1.2.3