From 09a9982016499daeb3fbee5ac8d87797310a565a Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 19 Nov 2015 11:43:09 +0100 Subject: [PATCH] timekeeping: Lift clocksource cacheline restriction We cache all hotpath members of a clocksource in the time keeper core. So there is no requirement in general to cache line align struct clocksource. Remove the enforces alignment. That allows users which need to wrap struct clocksource into their own struct to align the struct without getting extra padding. Signed-off-by: Thomas Gleixner Cc: John Stultz Cc: Russell King - ARM Linux Cc: Marc Gonzalez Cc: Daniel Lezcano Cc: Mans Rullgard Cc: Viresh Kumar Cc: Nicolas Pitre Cc: Tony Lindgren Cc: Sebastian Frias Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1511191209000.3898@nanos --- include/linux/clocksource.h | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 7784b597e959..6013021a3b39 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -62,12 +62,18 @@ struct module; * @suspend: suspend function for the clocksource, if necessary * @resume: resume function for the clocksource, if necessary * @owner: module reference, must be set by clocksource in modules + * + * Note: This struct is not used in hotpathes of the timekeeping code + * because the timekeeper caches the hot path fields in its own data + * structure, so no line cache alignment is required, + * + * The pointer to the clocksource itself is handed to the read + * callback. If you need extra information there you can wrap struct + * clocksource into your own struct. Depending on the amount of + * information you need you should consider to cache line align that + * structure. */ struct clocksource { - /* - * Hotpath data, fits in a single cache line when the - * clocksource itself is cacheline aligned. - */ cycle_t (*read)(struct clocksource *cs); cycle_t mask; u32 mult; @@ -95,7 +101,7 @@ struct clocksource { cycle_t wd_last; #endif struct module *owner; -} ____cacheline_aligned; +}; /* * Clock source flags bits::