Messages in this thread Patch in this message | | | From | Viresh Kumar <> | Subject | [PATCH 1/3] timer: Allocate per-cpu tvec_base's statically | Date | Mon, 30 Mar 2015 10:47:17 +0530 |
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From: Peter Zijlstra <peterz@infradead.org>
Memory for tvec_base is allocated separately for boot CPU (statically) and non-boot CPUs (dynamically).
The reason is because __TIMER_INITIALIZER() needs to set ->base to a valid pointer (because we've made NULL special, hint: lock_timer_base()) and we cannot get a compile time pointer to per-cpu entries because we don't know where we'll map the section, even for the boot cpu.
This can be simplified a bit by statically allocating per-cpu memory. The only disadvantage is that memory for one of the structures will stay unused, i.e. for the boot CPU, which uses boot_tvec_bases.
This will also guarantee that tvec_base is cacheline aligned. Even though tvec_base has ____cacheline_aligned stuck on, kzalloc_node() does not actually respect that (but guarantees a minimum u64 alignment).
Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- kernel/time/timer.c | 36 ++++++++---------------------------- 1 file changed, 8 insertions(+), 28 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 2d3f5c504939..6e8220ec8a62 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -93,6 +93,7 @@ struct tvec_base { struct tvec_base boot_tvec_bases; EXPORT_SYMBOL(boot_tvec_bases); static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases; +static DEFINE_PER_CPU(struct tvec_base, __tvec_bases); /* Functions below help us manage 'deferrable' flag */ static inline unsigned int tbase_get_deferrable(struct tvec_base *base) @@ -1534,46 +1535,25 @@ EXPORT_SYMBOL(schedule_timeout_uninterruptible); static int init_timers_cpu(int cpu) { - int j; - struct tvec_base *base; + struct tvec_base *base = per_cpu(tvec_bases, cpu); static char tvec_base_done[NR_CPUS]; + int j; if (!tvec_base_done[cpu]) { static char boot_done; - if (boot_done) { - /* - * The APs use this path later in boot - */ - base = kzalloc_node(sizeof(*base), GFP_KERNEL, - cpu_to_node(cpu)); - if (!base) - return -ENOMEM; - - /* Make sure tvec_base has TIMER_FLAG_MASK bits free */ - if (WARN_ON(base != tbase_get_base(base))) { - kfree(base); - return -ENOMEM; - } - per_cpu(tvec_bases, cpu) = base; + if (!boot_done) { + boot_done = 1; /* skip the boot cpu */ } else { - /* - * This is for the boot CPU - we use compile-time - * static initialisation because per-cpu memory isn't - * ready yet and because the memory allocators are not - * initialised either. - */ - boot_done = 1; - base = &boot_tvec_bases; + base = per_cpu_ptr(&__tvec_bases, cpu); + per_cpu(tvec_bases, cpu) = base; } + spin_lock_init(&base->lock); tvec_base_done[cpu] = 1; base->cpu = cpu; - } else { - base = per_cpu(tvec_bases, cpu); } - for (j = 0; j < TVN_SIZE; j++) { INIT_LIST_HEAD(base->tv5.vec + j); INIT_LIST_HEAD(base->tv4.vec + j); -- 2.3.0.rc0.44.ga94655d
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